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Impact of agricultural inputs on soil organisms--a review.

Introduction

Agricultural inputs

External inputs to agricultural production systems include mineral fertilisers such as urea, ammonium nitrate, sulfates, and phosphates; organic fertilisers such as animal manures, composts, and biosolids; various other organic products such as humic acids and microbial inoculants, and pesticides including herbicides, insecticides, nematicides, fungicides, veterinary health products, and soil fumigants. All these products are applied with the ultimate goal of maximising productivity and economic returns.

Mineral fertilisers are a major physical input into Australian agricultural production and account for over 12% of the value of material and services inputs used (Fertilizer Industry Federation of Australia Inc., www.fifa.asn.au). In 1999, Australian farmers used around 5.25 million t of fertiliser products with a value of approximately AU$2 billion. Common types of mineral fertilisers and their abbreviations as used in this review are shown in Table 1. Manures from intensive animal industries are a major source of organic amendments for agricultural land. In Australia, beef and dairy cattle alone produce approximately 4 million t of manure every year. Human waste is another important source. Sydney, Australia's largest urban area, produces 185 000 t of biosolids each year (Sydney Water Annual Report 2004). Nearly all of this is used for land amendment, either as dewatered solids, lime-stabilised solids, or in composts with green wastes. Pesticides are a diverse group of inorganic and organic chemicals. More than 380 active constituent pesticides are currently registered in Australia (Record of Approved Active Constituents at: www.apvma.gov.au). Pesticide inputs constitute a major cost for Australian agriculture. For herbicide inputs alone it was estimated at AU$571 million to annual winter crops in the 1998-99 growing season (Jones et al. 2005).

Soil organisms: groups, activities, methods

Soil organisms consist of the microflora (bacteria and fungi) and the soil fauna (protozoa and invertebrate groups such as nematodes, mites, and earthworms). They influence the availability of nutrients for crop production via a range of activities such as the decomposition of crop residues, immobilisation of nutrients, mineralisation, biological nitrogen fixation, and bioturbation. The soil fauna is crucial for the initial comminution and mixing of residues into the soil, whilst the microflora has a greater suite of enzymes for chemical breakdown of organic material (Paul and Clark 1996). Bacteria and fungi are often considered as a labile pool of nutrients (C, N, P, S) called the soil microbial biomass that has a pivotal role in nutrient immobilisation and mineralisation. The release of nutrients from the microbial biomass is partly regulated through grazing by the soil fauna.

The effect of agricultural inputs on soil organisms can be measured either as changes in the amount of single organisms, organism groups or methodologically defined pools such as the microbial biomass, or as changes in biological activity, e.g. soil respiration and enzyme activities. The most commonly used methods are listed and explained in Table 2. Variable effects of a given amendment on different organisms may change the composition of the microbial (or faunal) community without changing total amounts or activities. However, most studies have focussed on the soil microbial biomass as the central pool in nutrient cycling.

Concept of this review

In this paper we summarise the current understanding of the effects of inorganic and organic agricultural inputs on soil organisms. The underlying concept is that these inputs can affect soil organisms through direct or indirect effects (Table 3). Direct effects via changes in nutrient availability or toxicity will become already apparent in the first season after the application or in the longer term if repeated additions are required to reach a threshold above which effects are seen. Indirect effects will usually take more than one season to establish, especially when changes in soil organic matter levels are involved. In the case of long-term data, it can be difficult to separate direct and indirect effects.

Existing data are presented for the different amendments separately but discussed together. The evidence from Australia is rather limited, and therefore the review includes literature from overseas, in an attempt to establish the main principles and to draw some conclusions applicable to agro-ecosystems in Australia.

Mineral fertilisers

Most mineral fertiliser in Australia and elsewhere is applied to systems with regular and significant nutrient exports in harvested products, i.e. to grasslands and land under arable cropping. Experimental approaches to assess the effect of mineral fertilisers range from laboratory incubations, pot experiments, and 1-season studies in the field to long-term field experiments and sampling of paired sites under different management, thus covering time frames from days to more than 1 O0 years. In an attempt to separate direct from indirect effects, in the following sections we have compiled studies according to their experimental approach and time frame.

Laboratory incubations

Laboratory incubations allow the study of short-term effects under controlled conditions, i.e. in the absence of plants, climatic variation, and external inputs or losses. We found, however, very limited and often contradictory results from laboratory studies. For example, the addition of 200 mg N/kg soil as ammonium sulfate to 2 pasture soils of varying P status from New Zealand resulted in a decrease in microbial P, no change in the turnover of added C, and an increase in N mineralisation during 168 days of incubation (Saggar et al. 2000). An earlier study from New Zealand had, however, found an increase in soil respiration and microbial P, but no effect on microbial N and a decrease in various enzyme activities upon addition of 500 mg P/kg soil as calcium diphosphate (Haynes and Swift 1988). The addition of N, P, K, and S at 100, 20, 100, and 20mg/kg soil, respectively, to a range of soils from southern Australia, followed by incubation for 20 days, resulted in minor changes (increase or decrease) of soil respiration and microbial C, N, and P that remained within 20% difference from the non-amended controls (Bunemann, unpublished). Remarkably, changes in microbial C, N, and P were not interrelated.

Contradicting evidence such as an increase in microbial P while microbial C and N are unaffected might be interpreted as shifts in the composition of the microbial community. This possibility has been investigated in recent studies using biochemical markers and molecular techniques. The addition of N did not change the community composition as indicated by the phospholipid fatty acid (PLFA) profile in a study where total soil respiration was unaffected, but peroxidase activity and the preferential use of older, more stable soil organic matter increased after N addition (Waldrop and Firestone 2004). In 2 studies from Germany, ammonium addition did not change the composition of the microbial community during 28 days of incubation (Avrahami et al. 2003a), but led to community shifts after 16 weeks of incubation (Avrahami et al. 2003b). Using molecular techniques in a range of pot experiments, Marschner et al. (2004) showed that soil pH and N and P fertilisation can affect the microbial community composition, but that substrate availability, e.g. in the form of root exudates in the rhizosphere, appears to be the main factor determining the community composition in the rhizosphere. It is thus important to consider the potential feedback from improved plant nutrition when examining fertiliser effects on soil organisms.

Pot experiments and field studies

Pot experiments (Table 4) have mainly been used to investigate the effect of mineral P and N fertiliser on root colonisation by arbuscular mycorrhizal fungi (AMF). Whereas the addition of mineral N did not affect AMF, increasing additions of inorganic P decreased the rate of root length colonisation in 2 cases (Ryan and Ash 1999; Rubio et al. 2003). A decrease in AMF root colonisation was also observed in pastures after 15-17 years of mineral P and N fertilisation (Ryan et al. 2000).

Many field experiments have shown a lack of response of the microbial biomass and earthworms to mineral fertilisers (Table 4), even in cases where pasture production increased (e.g. Perrott et al. 1992; Sarathchandra et al. 1993). Where a decrease in microbial C was observed, it was usually accompanied by a decrease in soil pH after application of N or S fertilisers (e.g. Gupta et al. 1988; Ladd et al. 1994; Sarathchandra et al. 2001). Other methods such as microbial enumeration by plate counts (Sarathchandra et al. 1993), enzyme activities (Graham and Haynes 2005), and nematode counts (Parfitt et al. 2005), which are possibly more sensitive than measurements of microbial biomass, show variable changes due to mineral fertilisation (Table 4). For example, although the total number of nematodes was not affected by N fertilisation and a concomitant decrease in pH, some nematode species increased, whereas others were decreased (Sarathchandra et al. 2001).

The absence of changes in microbial C in response to N fertilisation and a related decrease in pH in the 2 long-term field experiments studied by Moore et al. (2000) are interesting, because in the same study microbial C was found to be correlated to levels of organic C (OC) as induced by different crop rotations. Several long-term field experiments in which mineral and organic fertiliser inputs have been compared (Table 5) have likewise shown good correlations between the microbial biomass and soil organic C (Witter et al. 1993; Houot and Chaussod 1995; Leita et al. 1999). Although soil organic C levels are often increased by mineral fertilisation compared with the non-fertilised control, even greater increases in soil organic C are usually achieved in treatments receiving organic amendments. This is also reflected in the fact that whereas mineral fertilisers show variable effects on soil organisms, organic amendments have only been reported to have insignificant or positive long-term effects (Table 5). The only exception was a decrease in microbial C after sewage sludge application, which also decreased soil pH (Witter et al. 1993). These observations point towards the role of C inputs, either with the organic amendment, or indirectly via increased plant growth and resulting plant residue input.

Graham et al. (2002) investigated the amounts of microbial C and N under sugarcane after 59 years of differential crop residue management and NPK fertilisation and showed that the microbial biomass was directly influenced by residue management and indirectly by NPK fertilisation through increased residue inputs. A follow-up study in the same trial revealed the interaction of soil acidification with negative effects and organic matter accumulation with positive effects on soil organisms and enzyme activities (Graham and Haynes 2005). The long-term field experiment studied by Houot and Chaussod (1995) exemplifies that agro-ecosystems can be relatively slow to respond to changes in management and thus illustrates the value of long-term field experiments. The excellent correlation between microbial C and soil organic C found after > 100 years of constant management practices remained disturbed 2 years after a change in crop rotation and crop residue management. The time required to reach a new equilibrium is a factor that may confound the results from many short-term studies.

Another potential indirect effect of fertiliser inputs was investigated in a long-term fertilisation experiment without plants (Pernes-Debuyser and Tessier 2004). The comparison of various N, P, and K fertilisers, liming, and manure treatments revealed that ammonium fertilisers decreased pH and CEC, causing a degradation of hydraulic properties, whereas basic amendments increased pH and CEC. Aggregate stability was lowest in acid plots, intermediate in basic plots, and highest in plots treated with manure. A short-term study suggested that ammonium nitrate enhanced soil porosity by 18%, compared with 46% increase in a manure treatment. Since soil respiration almost doubled in the mineral fertiliser treatment compared with the unfertilised control, the authors discussed a potential priming effect of N addition on the decomposition of soil organic matter. Although such a priming effect is often observed (Kuzyakov et al. 2000), it seems to be rather short-lived, which might explain why we did not find much evidence for it (Table 4).

A decreased amount or activity of soil organisms after mineral fertilisation could be due to the toxicity of metal contaminants contained in mineral fertilisers. In general, N and K fertilisers contain very low levels of contaminants, whereas P fertilisers often contain significant amounts of cadmium, mercury, and lead (McLaughlin et al. 2000). Metal contaminants are, however, most prevalent in waste products from urban and industrial areas and will be dealt with more in-depth in the section on organic fertilisers. Long-term chronic toxicity due to gradually accumulating metals appears to be far more common than immediate, acute toxicity (Giller et al. 1998). Quality control of fertiliser products is therefore required. This applies in particular to any new products. For example, the application of rare earth elements such as lanthanum, which is increasing in China, was shown to decrease soil respiration and dehydrogenase activity at high application rates (Chu et al. 2003). Such observations warrant more detailed investigation into processes of accumulation, bioavailability, and threshold levels of elements contained in fertilisers that can be toxic to soil organisms.

Organic fertilisers

Since most organic fertilisers are waste products, their application rate is often determined by availability rather than demand. Most amendments are applied primarily to benefit plant growth. In contrast to mineral fertilisers, however, effects on the soil's physical, chemical, and biological properties are sometimes intended as well (Table 6). In the following sections, we try to establish some links between the properties of various organic inputs and their effects on soil organisms.

Compostable organics

Compostable and composted materials vary widely in characteristics such as dry matter content, pH, salinity, carbon content, plant nutrient concentrations, non-nutrient elements, and microbial types, numbers, and activity. Although studies of amendments vary widely in nature of materials, application rates, and experimental conditions (Albiach et al. 2000), amendment with raw and composted organics generally results in increased microbial proliferation in the soil (Table 7). The duration of observed increases in soil organisms depends on the amount and proportions of readily decomposable carbon substrates added and the availability of nutrients, particularly nitrogen (Hartz et al. 2000; Adediran et al. 2003). However, microbial characteristics of amended soils often return to their baseline within a few years (Speir et al. 2003; Garcia Gil et al. 2004). Sustained changes in microbial biomass, diversity, and function are more likely where organic amendments are ongoing, as is the case in organic and biodynamic farms (Mader et al. 2002; Zaller and Kopke 2004). Ryan (1999) argues, however, that an increase in microbial populations may not be seen when system productivity is limited by nutrient input or water supply.

Manures and sewage sludge generally have higher salinity than municipal garden wastes, and salts can build up in soil with repeated heavy applications (Hao and Chang 2003; Usman et al. 2004). Sewage sludges (biosolids) often contain heavy metals such as copper, zinc, or cadmium, especially where industries contribute to the waste stream. Heavy metals can affect microbial processes more than they affect soil animals or plants growing on the same soils. For example, nitrogen-fixing rhizobia were far more sensitive to metal toxicity than their host plant clover. This resulted in N deficiency of clover due to ineffective rhizobia in sludge-amended soils (Giller et al. 1998). Sewage sludge and livestock manure may also contain active residues of therapeutic agents used to treat or cure diseases in humans and animals (Jjemba 2002). Green wastes from farms and gardens are typically lower in nutrient concentrations than manures or sewage sludges, but may contain residues of synthetic compounds such as herbicides, insecticides, fungicides, and plant growth regulators. Composting degrades some but not all such compounds, depending on the nature of the pesticide and the specific composting conditions (Buyuksonmez et al. 2000). Negative effects of heavy metals (Giller et al. 1998) can persist for many years following cessation of application (Abaye et al. 2005), since metals persist in soil practically indefinitely (McLaughlin et al. 2000). Such observations warrant strict regulations of organic fertiliser quality and applied quantity, especially of waste products such as sewage sludge and biosolids, in order to minimise contamination of agricultural land with toxic metals.

Humic substances

Humus in soil has traditionally been separated into humin, humic acid, and fulvic acid based on extraction with an alkaline solution and subsequent precipitation after addition of an acid (Swift 1996). The fractions typically rank in their resistance to microbial decomposition in the order humic acid > fulvic acid > humin (Qualls 2004). Concentrated sources of organic material such as peat, composts, and brown coal (oxidised coal, lignite, leonardite) also contain humic substances and are often marketed on the basis of their humic and fulvic acid contents as determined by similar procedures. Contents of humic acids vary, however, widely (Riffaldi et al. 1983). Some of the chemically extracted humic and fulvic acid separates are themselves sold as soil amendments. In discussion of organic amendments, a clear distinction must be made between products containing humic substances and those products that are humic (or fulvic) acids extracted from the primary sources listed above.

Humic substances can stimulate microbial activity directly through provision of carbon substrate, supplementation of nutrients, and enhanced nutrient uptake across cell walls (Valdrighi et al. 1996). Several studies showed that increasing amounts of compost or brown coal-derived humic acid stimulated aerobic bacterial growth, but had only slight effects on actinomycetes and no effect on filamentous fungi (Vallini et al. 1993; Valdrighi et al. 1995, 1996). Differences in microbial response were related to the molecular weight of the humic acids, with the lower weight fractions, typical of composts, causing greater microbial stimulation than the higher molecular weight fractions extracted from brown coal (Garcia et al. 1991; Valdrighi et al. 1995). Application of humic substances may induce changes in metabolism, allowing organisms to proliferate on substrates which they could not previously use (Visser 1985). Both heterotrophic and autotrophic bacteria can be stimulated by humic acid addition, mostly through the enhanced surfactant-like absorption of mineral nutrients, although heterotrophs also benefit from the direct uptake of organic compounds (Valdrighi et al. 1996). Vallini et al. (1997) showed that nitrifiers (chemotrophs) cannot use humic acids as an alternative carbon and energy source. Microbial activity may even be inhibited if humic acid is the sole carbon source (Filip and Tesarova 2004).

The principal indirect effects of humic substances on soil organisms are through increased plant productivity by mechanisms as listed in Table 6, but excessive applications can negatively affect plant growth (Fagbenro and Agboola 1993; Vallini et al. 1993; Valdrighi et al. 1995; Atiyeh et al. 2002), possibly through reduced availability of chelated nutrients (Chen et al. 2004). Field studies vary widely in the applied amounts of humic substances and in outcomes. Kim et al. (1997a) found no effect of commercial humate applied at 8.2t/ha on microbial activity or microbial functional groups (total fungi, actinomycetes, total Gram-negative bacteria, fluorescent pseudomonads, and P. cupsici) in a sandy soil used to grow bell peppers. Similarly, after 5 years of annual applications of 100 L/ha liquid humic acid to a horticultural soil, Albiach et al. (2000) found no effect on microbial biomass or enzyme activity. They ascribed the lack of effect to the low rates recommended by the manufacturer because of high product costs. Municipal solid waste compost and sewage sludge were more affordable and led to significant increases in microbial biomass in the same study. Only fungi were stimulated by humate added to soil being restored post-mining (Gosz et al. 1978), whereas Whiteley and Pettit (1994) found that lignite-derived humic acid inhibited decomposition of wheat straw. Chen et al. (2004) calculated from laboratory studies that 67.5 kg/ha of humic substances were needed for effective application to a sandy soil, but thought beneficial effects to plants may only occur in semi-arid or arid areas when applied in combination with irrigation and mineral nutrients.

Microbial inoculants

Inoculation with natural or genetically engineered microbial formulations can be broadly categorised according to whether they are intended to (a) exist on their own in the bulk soil, (b) populate the rhizosphere, (c) form symbiotic associations with plants, or (d) promote microbial activity on leaf or straw surfaces. To achieve the desired effect in the field, the inoculant organism must not only survive but establish itself and dominate in the soil or rhizosphere. Survival depends firstly on the quality of the inoculant itself, i.e. purity, strain trueness, viable numbers, the degree of infectivity, and level of contaminants (Abbott and Robson 1982; Kennedy et al. 2004). Secondly, the establishment and proliferation of inoculant in the soil environment are determined by many edaphic and climatic factors, the presence of host organisms (for symbionts and endophytes) and, most importantly, by competitive interactions with other microorganisms and soil fauna (Stotzky 1997; Slattery et al. 2001; McInnes and Haq 2003). Effects of inoculation on indigenous soil organisms can therefore either result from direct addition effects and interactions with indigenous soil organisms, or from indirect effects via increases in plant growth by one or several of the mechanisms listed in Table 6.

Positive effects of inoculants on the soil microbial biomass may be short-lived (Kim et al. 1997b), and increases in biomass or activity can even be due to the indigenous population feeding on the newly added microorganism (Bashan 1999). The most successful and widely studied inoculants are the diazotroph bacteria (Rhizobium, Bradyrhizobium, Sinorhizobium, Frankia) used for symbiotic fixation of [N.sub.2] from air. Provided soil conditions are favourable for rhizobia survival (Slattery et al. 2001), inoculation can increase microbial C and N in the rhizosphere compared with uninoculated soils (Beigh et al. 1998; Moharram et al. 1999). Population changes can be limited to the season of inoculation if the newly added organism is not as well adapted to the soil conditions as the indigenous population (McInnes and Haq 2003).

Inoculant application research is increasingly focussing on co-inoculation with several strains or mixed cultures enabling combined niche exploitation, cross-feeding, complementary effects, and enhancement of one organism's colonisation ability when co-inoculated with a rhizosphere-competent strain (Goddard et al. 2001). An example is the use of phosphorus-solubilising bacteria to increase available phosphorus along with mycorrhizae that enhance phosphorus uptake into the plant (Kim et al. 1997b). Saini et al. (2004) achieved maximum yields of sorghum and chickpea at half the recommended rates of inorganic fertiliser when a combination of mycorrhizae, [N.sub.2]-fixing bacteria, and phosphorus-solubilising bacteria was added. Increases in microbial biomass C, N, and P in soils of inoculated treatments were strongly correlated with N and P uptake of the plants. Garbaye (1994) suggested that specific 'helper' bacteria may improve the receptivity of the root to the fungus to enhance mycorrhizal colonisation and symbiotic development with plant roots (e.g. Founoune et al. 2002). Similarly, legume root nodulation can be enhanced by co-inoculation with Azospirillum, which increases root production and susceptibility for rhizobium infection and may also increase secretion of flavonoids from roots that activate nodulation genes in Rhizobium (Burdman et al. 1996). Conn and Franco (2004) found a significant reduction in indigenous actinobacterial endophytes upon inoculation of soil with a commercial multi-organism product, compared with no change in diversity after inoculation with a single species. Trial with 'effective microorganisms' (EM), a proprietary combination of photosynthetic bacteria, lactic acid bacteria, and yeasts used as a soil and compost inoculant, showed enhanced soil microbial biomass, plant growth, and produce quality (Daly and Stewart 1999; Cao et al. 2000). The interactions of microbial inoculants with indigenous soil organisms are likely to be complex, and a better mechanistic understanding is necessary to predict short- and long-term effects.

Pesticides

The results from our literature survey on the effects of selected pesticides on soil organisms are shown in Table 8 (herbicides), Table 9 (insecticides and nematicides), Table 10 (fungicides), and Table 11 (veterinary health products, fumigants, and biological/non-chemical products). Although more than 380 active constituent pesticides are currently registered in Australia, this current review has found data on the effects of only 55 of these on soil organisms. There is clearly a paucity of data in both the Australian and international literature on the effects of a large number of pesticides on soil organisms. Additional data may be available in the chemical reviews of the Australian Pesticide and Veterinary Medicines Authority (www.apvma.gov.au), but much of the information is contained within confidential company reports. Some of the chemicals such as DDT and chloropicrin are no longer registered for use in Australia; however, data have been included in this review as their use continues in many countries.

Herbicides

The herbicides (Table 8) generally had no major effects on soil organisms, with the exception of butachlor, which was shown to be very toxic to earthworms at agricultural rates (Panda and Sahu 2004). The authors showed, however, that butachlor had little effect on acetylcholinesterase activity. Butachlor is not registered for use in Australia. Phendimedipham induced avoidance behaviour in earthworms (Amorim et al. 2005) and collembola (Heupel 2002). These effects are expected to be relatively short lived, as phendimedipham is broken down moderately rapidly (25-day half-life) in soil (Tomlin 1997). Other effects of herbicides on soil organisms were mainly isolated changes in enzyme activities. Glyphosate, for example, was shown to suppress the phosphatase activity by up to 98% (Sannino and Gianfreda 2001) in a laboratory study; however, urease activity was stimulated by glyphosate as well as atrazine.

Insecticides

Insecticides (Table 9) were generally shown to have a greater direct effect on soil organisms than herbicides. Organophosphate insecticides (chlorpyrifos, quinalphos, dimethoate, diazinon, and malathion) had a range of effects including changes in bacterial and fungal numbers in soil (Pandey and Singh 2004), varied effects on soil enzymes (Menon et al. 2005; Singh and Singh 2005), as well as reductions in collembolan density (Endlweber et al. 2005) and earthworm reproduction (Panda and Sahu 1999). Carbamate insecticides (carbaryl, carbofuran, and methiocarb) had a range of effects on soil organsism, including a significant reduction of acetylcholinesterase activity in earthworms (Ribera et al. 2001; Pandey and Singh 2004), mixed effects on soil enzymes (Sannino and Gianfreda 2001), and inhibition of nitrogenase in Azospirillum species (Kanungo et al. 1998). Persistent compounds including arsenic, DDT, and lindane caused long-term effects, including reduced microbial activity (Van Zwieten et al. 2003), reduced microbial biomass, and significant decreases in soil enzyme activities (Ghosh et al. 2004; Singh and Singh 2005).

Fungicides

Fungicides (Table 10) generally had even greater effects on soil organisms than herbicides or insecticides. As these chemicals are applied to control fungal diseases, they will also affect beneficial soil fungi and other soil organisms. Very significant negative effects were found for copper-based fungicides, which caused long-term reductions of earthworm populations in soil (Van Zwieten et al. 2004; Eijsackers et al. 2005; Loureiro et al. 2005). Merrington et al. (2002) further demonstrated significant reductions in microbial biomass, while respiration rates were increased, and showed conclusively that copper residues resulted in stressed microbes. Other observed effects included the reduced degradation of the insecticide DDT (Gaw et al. 2003). These negative effects are likely to persist for many years, as copper accumulates in surface soils and is not prone to dissipative mechanisms such as biodegradation. Negative effects were also found for benomyl, which caused long-term reductions in mycorrhizal associations (Smith et al. 2000). Two fungicides, ehlorothalonil and azoxystrobin, have recently been shown to affect on a biocontrol agent used for the control of Fusarium wilt (Fravel et al. 2005), illustrating potential incompatibilities of chemical and biological pesticides.

Veterinary health products, soil fumigants, and non-chemical products

Veterinary health products (Table 11) include a range of nematicides, hormones, and antimicrobials. Data on the potential effect of these compounds on soil organisms are quite limited. The antimicrobials tylosin, oxytetracycline, and sulfachloropyridazine reduced Gram-positive bacterial populations and inhibited microbial respiration (Vaclavik et al. 2004), which is in accordance with changes in the microbial community structure after tylosin addition (Westergaard et al. 2001). The broad-spectrum anti-parasite Ivermectin was shown to be toxic to collembola at concentrations as low as 0.26 mg/kg soil; however, it was far less toxic to enchytraeid worms (Jensen et al. 2003) and earthworms (Svendsen et al. 2005).

Soil fumigants are designed to eliminate harmful soil organisms and any competition for soil resources between soil organisms and the crop. In spite of this, soil fumigants have not always been found to have significant effects on soil organisms (Table 11). Confirmed long-term effects on various soil functions (Karpouzas et al. 2005) are, however, a serious concern. The long-term effects of fumigants were shown to be reduced by the addition of composted steer manure, with normal biological activity being observed 8-12 weeks following high application rates of the fumigant (Dungan et al. 2003). In the absence of the organic amendment, little recuperation (resilience) of soil function was detected even after 12 weeks.

Microorganisms have been used to control plant diseases for over 100 years (Winding et al. 2004). However, risks of biological control agents are often forgotten. Although the selected microbes may occur naturally in the environment, there are concerns that altering the proportion of soil microbes will affect non-target species including mycorrhizal and saprophytic fungi, soil bacteria, plants, insects, aquatic and terrestrial animals, and humans (Brimner and Boland 2003). In a recent review of non-target effects of bacterial control agents suppressing root pathogenic fungi, Winding et al. (2004) concluded that significant non-target effects occurred that were, however, generally short lived. Residues from genetically modified maize expressing a protein from Bacillus thuringiensis (Bt) that is toxic to corn borers were found to decompose similarly to residues from conventional maize (Cortet et al. 2006), although the Bt toxin did inhibit some decomposition processes under laboratory conditions (Accinelli et al. 2004). Other methods for pest control include technologies such as solarisation (Table 11). This method uses plastic sheeting to heat-sterilise the surface soil. Several authors found reductions in microbial biomass and bacterial diversity (Gelsomino and Cacco 2006; Patricio et al. 2006).

Pesticide formulation

In addition to the active ingredient, the formulation of a pesticide may also influence soil organisms. This is, however, an aspect that is rarely investigated. Little is known about the environmental fate of adjuvants after application on agricultural land. Adjuvants constitute a broad range of substances, of which solvents and surfactants are the major types. Non-ionic surfactants such as alcohol ethoxylates (AEOs) and alkylamine ethoxylates (ANEOs) are typical examples of pesticide adjuvants (Krogh et al. 2003). Tsui and Chu (2003) demonstrated that the surfactant in the Roundup formulation polyoxyethylene amine (POEA) was significantly more toxic to Microtox bacterium than glyphosate acid or the IPA salt of glyphosate. Even Roundup was found to be less toxic. The toxicity of glyphosate acid was concluded to be a result of its inherent acidity. In another study, dos Santos et al. (2005) demonstrated that the presence of ethylamine in a glyphosate formulation had major effects on Bradyrhizobium, whereas the active ingredient (glyphosate) had little if any effect. In formulation, effects included reduced nodulation in a soybean crop.

General discussion

Main findings and knowledge gaps

In agreement with the main focus of this journal, we attempted to base our review primarily on results from Australia and New Zealand. However, we found that the existing database on the effect of agricultural inputs on soil organisms in this region was far too limited to draw sound conclusions. Even when considering the global literature, we identified several knowledge gaps.

There was little evidence for significant direct effects of mineral fertilisers on soil organisms, whereas the main indirect effects were shown to be an increase in biological activity with increasing plant productivity, crop residue inputs, and soil organic matter levels, and a depression with decreasing soil pH as a result primarily of N fertilisation. This is in accordance with a review by Wardle (1992) who suggested that soil organic matter is the main factor governing levels of microbial biomass in soil, followed by soil pH. Long-term field experiments comparing mineral and organic fertilisers illustrated the role of indirect and direct carbon inputs into the soil in supporting biological activity. There is, however, a lack of such experiments in Australia and New Zealand.

Although direct C addition with the various organic amendments plays a major role in stimulating soil organisms, the role of C quality is not yet well understood. Compostable organics are an extremely diverse commodity with many potential benefits to soil organisms but also potential harmful effects, particularly with long-term application. Proper composting negates many potential harmful effects but not all. The toxic components that are not degraded or deactivated need to be identified and their specific effects better quantified. Australian standard AS 4454-2003 (Composts, soil conditioners and mulches) specifies threshold limits of heavy metals, pathogens, and organic compound contaminants based on demonstrated effects on plants and animals, not microorganisms, which may have a much lower threshold (Giller et al. 1998). As more and more of this material is used as a soil amendment rather than landfill, more research must be done on the long-term effects of the various contaminants on microorganisms.

The main problem with evaluating effects of specific products such as humic substances lies in the variety of materials of various origins, and in the fact that the properties are often defined by extraction methods that vary among laboratories and product manufacturers. Very few studies have investigated how humic substances affect soil organisms, and a closer examination of the effects of humic substances in laboratory cultures and soil cultures is required for an improved process understanding.

Microbial inoculants have mainly been studied under the aspect of inoculant survival and efficiency rather than with respect to effects on indigenous soil organisms. Apart from rhizobial and some mycorrhizal inoculants, much of the potential for microbial inoculants is yet to be realised. Possibly, the conventional scientific approach has been too reductionist, producing single strain organisms that often cannot compete in complex field situations (Marx et al. 2002). Since there is evidence that multi-organism products may be in a better position to compete with indigenous microorganisms, it is necessary to investigate the mechanisms in order to derive a causal understanding. Non-target effects of inoculants appear to be small and transient. However, Winding et al. (2004) point out that not enough is known about some marketed products aimed at disease control whose antimicrobial effects may extend beyond the growth season.

Among the pesticides, herbicides appeared to have the least significant effects on soil organisms, whereas some insecticides and especially some fungicides proved to be quite toxic. Few studies have investigated long-term effects of pesticide application, and even less discuss measured or observed changes to soil processes. One example is the lack of bioturbation noted recently in a copper-contaminated orchard (Van Zwieten et al. 2004). Copper has been shown to reduce the burrowing activity of earthworms, which in turn led to increased soil bulk density in a vineyard (Eijsackers et al. 2005). Likewise, Gaw et al. (2003) described the lack of pesticide breakdown in soils where copper was a co-contaminant. There is clear evidence that soil organisms and thus soil functions can be affected by pesticides, but comprehensive data showing which of these changes are long-term and reduce soil health are lacking.

Methodological issues

A broad range of tests has been used to evaluate effects of agricultural inputs on soil organisms, measuring the amount, activity, and diversity of soil organisms (Table 2). The lack of standardised methods often precludes a direct comparison between the various studies. Even if a similar method is used, slight variations in environmental conditions during the assay may change the outcome considerably, resulting, for example, in threshold levels of metal toxicity that can vary among studies by several orders of magnitude (Giller et al. 1999). Microbial endpoints have therefore sometimes been deemed to have limited use in risk assessment (Kapustka 1999). Ideally, endpoints should be highly sensitive to the respective contaminant while at the same time being robust, i.e. showing little variation among soils in the absence of the contaminant. However, when testing 8 ecotoxicological endpoints on 2 sets of soils, one metal-contaminated and one non-contaminated, Broos et al. (2005) observed a negative relationship between sensitivity and robustness of an endpoint. Therefore, a reasonable compromise might be to use endpoints of average sensitivity and good robustness. In their study, the lag-times of substrate-induced respiration, clover yield, and N fixation in clover were the most suitable endpoints for metal toxicity.

The most commonly measured variable, the microbial biomass, generally appears to be less sensitive to the various agricultural inputs than microbial activities such as soil respiration and enzyme activities. In the context of using microbial parameters to monitor soil pollution by heavy metals, Brookes (1995) suggested that the ratio of microbial activity and biomass, i.e. the metabolic quotient (Table 2), is more sensitive as an indicator of stress than either of the measurements alone.

Interpretation of enzyme activities in soil is complicated by the fact that enzymes may remain active when stabilised on organic matter or mineral surfaces. In addition, enzyme assays are usually based on the hydrolysis of artificial substrates such as p-nitrophenyl phosphate, but enzyme activity against natural substrates and under soil rather than assay conditions may be different. Enzyme activity against an artificial substrate must therefore be viewed as a potential activity and cannot be translated into actual reaction rates, and soil respiration may be a more direct measurement of microbial activity.

Methods to determine the microbial diversity have greatly advanced in recent years with the development of DNA-based techniques. However, even these methods still suffer from shortcomings such as the dependence of results on the extraction protocol (Martin-Laurent et al. 2001). Inoculation research has benefited from recent methodological advances, especially the development of molecular methods that allow following specific microorganism after addition into the soil--plant system (Marx et al. 2002; Conn and Franco 2004). Another technique is to genetically 'tag' newly released organisms to monitor the effects of introducing genetically modified organisms into the rhizosphere (Hirsch 2005). At the cellular level, direct staining techniques and advanced microscopy can provide high-resolution data on the metabolic activity and growth of inoculants (Schwieger et al. 1997).

Although laboratory studies are important to investigate basic processes, only field studies can fully elucidate the complex interactions of plants, soil, and climatic variation. Extrapolation from short-term tests is often not possible, especially when the mechanisms behind observed changes are not fully understood. This is especially true when long-term chronic toxicity poses a different stress on soil organisms than the immediate shock effect in laboratory tests (Giller et al. 1999). Only long-term monitoring in the field can provide the information required to establish regulatory guidelines, and an improved understanding of the system is mandatory for a sound risk assessment.

Interpreting changes in measured variables: where is the limit?

Our review has shown that most agricultural management strategies and external inputs can cause changes in the measured variables, whether they represent the amount, activity, or diversity of soil organisms. The challenge lies in interpreting the findings: we need to establish the limits for changes that are acceptable in view of that fact that agricultural inputs are a necessity, and those that are unacceptable, e.g. because they decrease biodiversity, impede soil functions, and diminish system productivity. Ultimately, the question is: what do we want to protect?

Terrestrial endpoints are often based on sensitive, threatened, and endangered species, such as the charismatic megafauna (Kapustka 1999). Measurements on soil organisms are, however, complicated by great spatial and temporal variation as well as complexity, since I g of soil can host more than 10 000 species of bacteria and an unknown diversity of fungi. In aquatic toxicology, an underlying assumption has sometimes been that if thresholds for toxic substances are based on the most sensitive species, then all species will be protected. However, the relative sensitivity of 2 species to chemical A may differ from that to chemical B. This concept is additionally complicated by the fact that an identified most-sensitive species may not be present in another ecosystem, making the application in regulatory terms questionable (Cairns 1986).

Protection of soil organisms based on their roles in nutrient cycling may be more practical and relevant for agroecosystems, even though it carries the risk that functional redundancy may mask changes in a population. Loss of specific functions that can only be carried out by very few species such as the loss of symbiotic nitrogen fixation due to application of metal-contaminated sewage sludge (Giller et al. 1998) or decreased decomposition due to detrimental effects of copper on earthworms (Van Zwieten et al. 2004) is obviously the biggest concern. Complete loss of function is, however, an exception rather than the rule.

When judging whether a change in a measured variable is of concern or not, the concept of Domsch et al. (1983) provides a good framework: a decrease in biological activity by up to 30% is deemed negligible, whereas a decrease by up to 90% could still be considered acceptable if it is followed by recovery within 30-60 days. This concept acknowledges the natural variation in many of the biological variables measured. It also places more emphasis on resilience than on resistance, where resistance is defined as the ability of the soil to withstand the immediate effects of perturbation, and resilience as the ability of the soil to recover from perturbation (Griffiths et al. 2001). Therefore, even laboratory tests should be run for a minimum of 30 days (Somerville et al. 1987). However, Giller et al. (1998) stress that a fundamental difference remains between acute toxicity (disturbance) and long-term chronic toxicity (stress), i.e. studying an adapting v. an adapted community. Thus, only long-term monitoring and field experiments can provide the information required to develop a sound risk assessment.

An increase in the amount, activity, or diversity of soil organisms is generally viewed as positive. However, an increase in the microbial biomass often goes along with increased nutrient immobilisation, at least temporarily, and an increase in soil organic matter can increase populations of detrimental organisms such as parasitic nematodes and root diseases. As stated above, it is the resilience of the system that matters. In terms of biodiversity, a mild stress can actually increase species diversity by reducing competition effects, before diversity decreases at higher stress levels (Giller et al. 1998). This exemplifies the difficulties in interpreting changes, especially those in biodiversity.

Dahlin et al. (1997) observed that detrimental effects of metal contamination at one site were seen at metal concentrations below the background concentrations at the other site and asked in exasperation: 'Where is the limit?' One answer may be that there is no distinct threshold for metal toxicity, or for detrimental effects of other inputs, partly because the effects depend on site-specific characteristics such as climate and soil type. In testing procedures for the side effects of pesticides on soil microorganisms it has long been recognised that effects are more likely to be seen on light-textured soils that are low in organic matter than on heavier soils, and it is therefore recommended to use at least 2 contrasting soil types (Somerville et al. 1987). Likewise, changes in soil pH are more likely to have detrimental effects on soil organisms closer to the extreme points of the scale. For these reasons, it is mandatory to always choose a valid control, i.e. to allow for site-specific differences in the baseline, and to interpret changes in the context of the given site-specific characteristics.

An approach to assess the relative risk of pesticides to an agroecosystem (EcoRR) has been developed in Australia (Sanchez-Bayo et al. 2002). The methodology uses site-specific data and accounts for chemical dose, partitioning (air, soil, vegetation, surface and ground water), degradation, bioconcentration, and toxicity. Another model (PIRI) has been developed in Australia to assess the risk of pesticides entering groundwater (Kookana et al. 1998) and thus affecting the environment and human health. Neither of these models assesses, however, the risk of pesticides to soil organisms or even more broadly, soil quality.

Concluding remarks

The underlying principle for the protection of soil organisms should be to limit or prevent exposure of organisms to unacceptable hazards (McLaughlin et al. 2000). Our review has shown that some drastic negative effects such as those of copper fungicides and, to a lesser degree, soil acidification on soil organisms, have to be considered urgently if soil health is to be maintained. For some classes of inputs such as humic acids and various pesticides, the existing database is simply too small to draw sound conclusions. The main lesson learnt from the fertiliser section, however, is that any practice that increases levels of soil organic matter will also increase soil biological activity.

Acknowledgments

The senior author thanks the Grains Research and Development Corporation for support while this review was compiled. Questions and comments by 2 anonymous reviewers helped to improve the manuscript. We are also grateful to Kris Broos for providing us with relevant ecotoxicological references.

Manuscript received 30 August 2005, accepted 11 April 2006

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E. K. Bunemann (A,D), G. D. Schwenke (B), and L. Van Zwieten (C)

(A) School of Earth and Environmental Sciences, University of Adelaide, Adelaide, SA 5000, Australia.

(B) Tamworth Agricultural Institute, NSW Department of Primary Industries, Calala, NSW 2340, Australia.

(C) Wollongbar Agricultural Institute, NSW Department of Primary Industries, Wollongbar, NSW 2477, Australia.

(D) Corresponding author. Email: else.bunemann@adelaide.edu.au
Table 1. Some common inorganic fertilisers and their
abbreviations as used in this review

Name                          Abbreviation

Ammonium nitrate              AN
Ammonium sulfate              AS
Calcium nitrate               CaN
Diammonium phosphate          DAP
Elemental sulfur              [S.sup.0]
Phosphate rock                PR
Sodium dihydrogen phosphate   NaHP
Superphosphate                SP
Triple superphosphate         TSP
Urea                          U

Table 2. Common methods to assess the amount, activity, and diversity
of soil organisms

Name                       Method description       Reference

                           Enumeration/amount

Microbial C                C in microbial biomass   Vance et al.
                             by fumigation-           (1987), Islam
                             extraction or            and Weil (1998)
                             microwave methods
Microbial N                N in microbial biomass   Vance et al.
                             by fumigation-           (1987), Amato
                             extraction methods       and Ladd (1988)
Microbial P                P in microbial biomass   Brookes et al.
                             by fumigation-           (1982), Kouno
                             extraction methods       et al. (1995)
Adenosine triphosphate     Extractable ATP          Contin et
                             indicates size of        al. (2001)
                             microbial biomass
Total bacterial DNA        PicoGreen dsDNA          Angersbach and
                                                      Earp (2004)
CFU                        Colony forming units;    e.g.
                             plate counting           Sarathchandra
                             techniques, e.g.         et al. (1993)
                             Gram--ve bacteria,
                             actinomycetes, fungi
AMF                        Arbuscular mycorrhizal   e.g. Ryan et
                             fungi; usually root      al. (2000)
                             colonisation
                             observed
Soil fauna                 Nematodes, collembola    e.g. Martikainen
                             (springtails),           et al. (1998),
                             enchytraeids,            Van Zwieten et
                             earthworms               al. (2003)
                             (sometimes in
                             combination with
                             avoidance tests)

                           Activity

Soil respiration           C[O.sub.2]-release       Alef (1995)
                             from incubated soil
Metabolic quotient         Ratio of soil            Anderson and
                             respiration to           Domsch (1990)
                             microbial C; higher
                             values can indicate
                             physiological stress
Soil enzyme activities     Dehydrogenase, acid      Tabatabai (1994)
                             and alkaline
                             phosphatase,
                             amidase, urease,
                             arylsulfatase, etc.
FDA hydrolysis             Fluorescein diacetate    Adam and
                             (FDA) hydrolysis as      Duncan (2001)
                             a measure of total
                             microbial activity
Acetylcholin-esterase      Activity of the enzyme   e.g. Panda and
  activity in earthworms     that hydrolyses          Sahu (2004)
                             acetylcholine in
                             the nervous system;
                             reduced activity
                             indicates toxicity

                           Diversity

PLFA and FAME              Phospholipid fatty       Drenovsky et
                             acid and fatty acid      al. (2004)
                             methyl esters and
                             analysis: indicate
                             changes in microbial
                             community
                             composition
DGGE                       Microbial diversity      e.g. Marschner
                             assessed by DNA          et al. (2004)
                             extraction,
                             amplification with
                             polymerase chain
                             reaction (PCR) and
                             differentiation by
                             denaturing gradient
                             gel electrophoresis
                             (DGGE)
Biolog                     Soil microbial           Konopka et
                             substrate                al. (1998)
                             utilisation
                             potential

Table 3. Potential effects of inorganic and organic agricultural
inputs on soil organisms

                                                Time frame (A)
Direct effects
* Increased amount and/or activity after        Short- to long-term
  removal of nutrient limitations
* Decreased activity due to high nutrient
  availability
* Decreased amount and/or activity due to
  toxicity

Indirect effects
* Change in pH                                  Long-term
* Change in soil physical properties
  (aggregation, porosity)
* Change in productivity, residue inputs, and
  soil organic matter levels

(A) Short-term, 1 season; long-term, more than 1 season.

Table 4. Effects of inorganic fertilisers on soil organisms as
observed in pot experiments and field studies

Reference and           Soil type and           Vegetation/
location                characteristics (A)     test plant

Ryan and Ash            Red-brown earth,        Pot exp with white
  (1999), Australia       pH 6, OC 26 g/kg        clover and
                                                  ryegrass
Rubio et al. (2003),    Volcanic soil, pH 5.5,  Pot exp with wheat
  Chile                   18% SOM
Sarathchandra et al.    Not given               Pasture
  (1993), NZ
Lovell and Hatch        36% clay                Pasture
  (1997), UK
Lupwayi et al.          Gray Luvisols and       Wheat-canola
  (2001), Canada          Black
                          Chernozems,
                          pH 5.7 and 7.3,
                          OC 28 and 47
                          g/kg
Perrott et al. (1992),  Yellow-brown earth,     Pasture
  NZ                      silt loam, pH 5.8,
                          OC 76 g/kg
Sarathchandra et al.    Umbric                  Pasture
  (2001), NZ              Dystrochrept,
                          sandy loam,
                          pH 5.7, OC 63
                          g/kg
                        Typic Hapludand, silt   > 10 years
                          loam, pH 4.9, OC
                          77 g/kg
Gupta et al. (1988),    Grey Luvisols,          Canola-fallow
  Canada                  pH 5.4 and 5.7,         rotation
                          OC 11 and 34
                          g/kg
Gupta and Germida       Grey Luvisol,           Pasture
  (1988); Gupta           pH 5.7, OC 28
  et al. (1988),          g/kg
  Canada
Ladd et al. (1994),     Red-brown earth,        Wheat rotations
  Australia               14% clay, pH 6.8,
                          OC 10 g/kg
Parfitt et al. (2005),  Typic Dystrudepts,      Pasture
  NZ                      pH 5.6-6.0, OC
                          32-11 t/ha in
                          0-7.5 cm
Ryan et al. (2000),     Mostly red-brown        Pasture
  Australia               earths, mean
                          pH 6.2, mean OC
                          2.6 g/kg
Moore et al. (2000),    Hapludoll, 22% clay     Maize-soybean-oat-
  USA                     and 31% sand,           meadow
                          mean pH 6.9,            rotations
                          mean OC 21 g/kg
                        Haplaquoll, 33%
                          clay and 24%
                          sand, mean
                          pH 6.2, mean OC
                          34 g/kg
Graham et al.           Chromic Vertisol,       Sugarcane
  (2002); Graham          58% clay, pH 5.8,
  and Haynes 2005,        OC 42 g/kg
  S. Africa

Reference and           Soil type and           Time
location                characteristics (A)     frame

Ryan and Ash            Red-brown earth,        5 weeks
  (1999), Australia       pH 6, OC 26 g/kg
Rubio et al. (2003),    Volcanic soil, pH 5.5,  6 months

  Chile                   18% SOM
Sarathchandra et al.    Not given               2 weeks
  (1993), NZ
                                                3 years
Lovell and Hatch        36% clay                10 weeks
  (1997), UK
Lupwayi et al.          Gray Luvisols and       1-2 seasons
  (2001), Canada          Black
                          Chernozems,
                          pH 5.7 and 7.3,
                          OC 28 and 47
                          g/kg
Perrott et al. (1992),  Yellow-brown earth,     2 years
  NZ                      silt loam, pH 5.8,
                          OC 76 g/kg
Sarathchandra et al.    Umbric                  4 years
  (2001), NZ              Dystrochrept,
                          sandy loam,
                          pH 5.7, OC 63
                          g/kg
                        Typic Hapludand, silt   100 P (SP)
                          loam, pH 4.9, OC
                          77 g/kg
Gupta et al. (1988),    Grey Luvisols,          2 years
  Canada                  pH 5.4 and 5.7,
                          OC 11 and 34
                          g/kg
Gupta and Germida       Grey Luvisol,           5 years
  (1988); Gupta           pH 5.7, OC 28
  et al. (1988),          g/kg
  Canada
Ladd et al. (1994),     Red-brown earth,        9-13 years
  Australia               14% clay, pH 6.8,
                          OC 10 g/kg
Parfitt et al. (2005),  Typic Dystrudepts,      7-23 years
  NZ                      pH 5.6-6.0, OC
                          32-11 t/ha in
                          0-7.5 cm
Ryan et al. (2000),     Mostly red-brown        15-17 years
  Australia               earths, mean
                          pH 6.2, mean OC
                          2.6 g/kg
Moore et al. (2000),    Hapludoll, 22% clay     19 years
  USA                     and 31% sand,
                          mean pH 6.9,
                          mean OC 21 g/kg
                        Haplaquoll, 33%         44 years
                          clay and 24%
                          sand, mean
                          pH 6.2, mean OC
                          34 g/kg
Graham et al.           Chromic Vertisol,       59-60 years
  (2002); Graham          58% clay, pH 5.8,
  and Haynes 2005,        OC 42 g/kg
  S. Africa

Reference and           Soil type and           Fertiliser
location                characteristics (A)     (kg/ha)

Ryan and Ash            Red-brown earth,        180 N (B) (AN)
  (1999), Australia       pH 6, OC 26 g/kg
                                                200 P (B) (NaHP)
Rubio et al. (2003),    Volcanic soil, pH 5.5,  17-86 P (TSP, PR)
  Chile                   18% SOM
Sarathchandra et al.    Not given               0-120 P (SP, PR)
  (1993), NZ
Lovell and Hatch        36% clay                40 N (AN)
  (1997), UK
Lupwayi et al.          Gray Luvisols and       20 S ([S.sup.0] or AS)
  (2001), Canada          Black
                          Chernozems,
                          pH 5.7 and 7.3,
                          OC 28 and 47
                          g/kg
Perrott et al. (1992),  Yellow-brown earth,     61 P (SP)
  NZ                      silt loam, pH 5.8,
                          OC 76 g/kg
Sarathchandra et al.    Umbric                  400 N (U)
  (2001), NZ              Dystrochrept,
                          sandy loam,
                          pH 5.7, OC 63
                          g/kg
                        Typic Hapludand, silt
                          loam, pH 4.9, OC
                          77 g/kg
Gupta et al. (1988),    Grey Luvisols,          50-100 S ([S.sup.0])
  Canada                  pH 5.4 and 5.7,
                          OC 11 and 34
                          g/kg
Gupta and Germida       Grey Luvisol,           44S ([S.sup.0])
  (1988); Gupta           pH 5.7, OC 28
  et al. (1988),          g/kg
  Canada
Ladd et al. (1994),     Red-brown earth,        0-80 N (AN)
  Australia               14% clay, pH 6.8,
                          OC 10 g/kg
Parfitt et al. (2005),  Typic Dystrudepts,      12-37 P, 12-26 S
  NZ                      pH 5.6-6.0, OC
                          32-11 t/ha in
                          0-7.5 cm
Ryan et al. (2000),     Mostly red-brown        27 P (SP, DAP), 17 N
  Australia               earths, mean            (U)
                          pH 6.2, mean OC
                          2.6 g/kg
Moore et al. (2000),    Hapludoll, 22% clay     180 N (U)
  USA                     and 31% sand,
                          mean pH 6.9,
                          mean OC 21 g/kg
                        Haplaquoll, 33%         180 N (U)
                          clay and 24%
                          sand, mean
                          pH 6.2, mean OC
                          34 g/kg
Graham et al.           Chromic Vertisol,       140 N, 20 P, 140 K
  (2002); Graham          58% clay, pH 5.8,
  and Haynes 2005,        OC 42 g/kg
  S. Africa

                                                Effect on soil
                                                organisms
                                                (amount and activity;
                                                % of control)

Reference and           Soil type and           Negative
location                characteristics (A)

Ryan and Ash            Red-brown earth,
  (1999), Australia       pH 6, OC 26 g/kg
                                                % Clover root length
                                                  colonised by
                                                  AMF (20-30%)
Rubio et al. (2003),    Volcanic soil, pH 5.5,  % Root colonisation
  Chile                   18% SOM                 (60-90%)
Sarathchandra et al.    Not given
  (1993), NZ
Lovell and Hatch        36% clay
  (1997), UK
Lupwayi et al.          Gray Luvisols and       Diversity (Biolog)
  (2001), Canada          Black
                          Chernozems,
                          pH 5.7 and 7.3,
                          OC 28 and 47
                          g/kg
Perrott et al. (1992),  Yellow-brown earth,
  NZ                      silt loam, pH 5.8,
                          OC 76 g/kg
Sarathchandra et al.    Umbric                  Microbial C (80%),
  (2001), NZ              Dystrochrept,           diversity (Biolog),
                          sandy loam,             Meloidogyne
                          pH 5.7, OC 63           (10%).
                          g/kg                    plant-associated
                                                  (68%) and
                                                  fungal-feeding
                                                  (82%) nematodes
                        Typic Hapludand, silt   Microbial C,
                          loam, pH 4.9, OC        microbial
                          77 g/kg                 diversity (Biolog),
                                                  total nematodes
Gupta et al. (1988),    Grey Luvisols,          Fungal CFUs (38%),
  Canada                  pH 5.4 and 5.7,         protozoa
                          OC 11 and 34            (4-25%),
                          g/kg                    microbial C
                                                  (49-98%),
                                                  respiration
                                                  (67-86%)
Gupta and Germida       Grey Luvisol,           Microbial C (60%),
  (1988); Gupta           pH 5.7, OC 28           respiration (54%),
  et al. (1988),          g/kg                    hyphal length
  Canada                                          (24%), fungal
                                                  CFUs (23%),
                                                  protozoa
                                                  (29-71%)
Ladd et al. (1994),     Red-brown earth,        Microbial C
  Australia               14% clay, pH 6.8,       (68-86%)
                          OC 10 g/kg
Parfitt et al. (2005),  Typic Dystrudepts,
  NZ                      pH 5.6-6.0, OC
                          32-11 t/ha in
                          0-7.5 cm
Ryan et al. (2000),     Mostly red-brown        % Clover and grass
  Australia               earths, mean            root length
                          pH 6.2, mean OC         colonised by
                          2.6 g/kg                AMF (67-79%)
Moore et al. (2000),    Hapludoll, 22% clay
  USA                     and 31% sand,
                          mean pH 6.9,
                          mean OC 21 g/kg
                        Haplaquoll, 33%
                          clay and 24%
                          sand, mean
                          pH 6.2, mean OC
                          34 g/kg
Graham et al.           Chromic Vertisol,       Dehydrogenase,
  (2002); Graham          58% clay, pH 5.8,       arylsulfatase,
  and Haynes 2005,        OC 42 g/kg              alkaline
  S. Africa                                       phosphatase

                                                Effect on soil
                                                organisms
                                                (amount and activity;
                                                % of control)

Reference and           Soil type and           No change
location                characteristics (A)

Ryan and Ash            Red-brown earth,        % Clover and rye
  (1999), Australia       pH 6, OC 26 g/kg        grass root length
                                                  colonized by
                                                  AMF
                                                % Ryegrass root
                                                  length colonised
                                                  by AMF
Rubio et al. (2003),    Volcanic soil, pH 5.5,
  Chile                   18% SOM
Sarathchandra et al.    Not given               Microbial P,
  (1993), NZ                                      earthworms
                                                Microbial P,
                                                  earthworms
Lovell and Hatch        36% clay                Microbial C and N
  (1997), UK
Lupwayi et al.          Gray Luvisols and       Microbial C
  (2001), Canada          Black
                          Chernozems,
                          pH 5.7 and 7.3,
                          OC 28 and 47
                          g/kg
Perrott et al. (1992),  Yellow-brown earth,     Microbial P and S
  NZ                      silt loam, pH 5.8,
                          OC 76 g/kg
Sarathchandra et al.    Umbric                  Total nematodes
  (2001), NZ              Dystrochrept,
                          sandy loam,
                          pH 5.7, OC 63
                          g/kg
                        Typic Hapludand, silt
                          loam, pH 4.9, OC
                          77 g/kg
Gupta et al. (1988),    Grey Luvisols,
  Canada                  pH 5.4 and 5.7,
                          OC 11 and 34
                          g/kg
Gupta and Germida       Grey Luvisol,           Bacterial and
  (1988); Gupta           pH 5.7, OC 28           actinomycetes
  et al. (1988),          g/kg                    CFUs
  Canada
Ladd et al. (1994),     Red-brown earth,        C and N
  Australia               14% clay, pH 6.8,       mineralisation
                          OC 10 g/kg
Parfitt et al. (2005),  Typic Dystrudepts,      Earthworms
  NZ                      pH 5.6-6.0, OC
                          32-11 t/ha in
                          0-7.5 cm
Ryan et al. (2000),     Mostly red-brown
  Australia               earths, mean
                          pH 6.2, mean OC
                          2.6 g/kg
Moore et al. (2000),    Hapludoll, 22% clay     Microbial C
  USA                     and 31% sand,
                          mean pH 6.9,
                          mean OC 21 g/kg
                        Haplaquoll, 33%         Microbial C
                          clay and 24%
                          sand, mean
                          pH 6.2, mean OC
                          34 g/kg
Graham et al.           Chromic Vertisol,       Protease, respiration
  (2002); Graham          58% clay, pH 5.8,
  and Haynes 2005,        OC 42 g/kg
  S. Africa

Reference and           Soil type and           Positive
location                characteristics (A)

Ryan and Ash            Red-brown earth,
  (1999), Australia       pH 6, OC 26 g/kg
Rubio et al. (2003),    Volcanic soil, pH 5.5,
  Chile                   18% SOM
Sarathchandra et al.    Not given               Fungi (480%), Gram
  (1993), NZ                                      -ve bacteria
                                                  -140%
Lovell and Hatch        36% clay                Nitrification,
  (1997), UK                                      ammonification
Lupwayi et al.          Gray Luvisols and
  (2001), Canada          Black
                          Chernozems,
                          pH 5.7 and 7.3,
                          OC 28 and 47
                          g/kg
Perrott et al. (1992),  Yellow-brown earth,
  NZ                      silt loam, pH 5.8,
                          OC 76 g/kg
Sarathchandra et al.    Umbric                  Paratvlenchus
  (2001), NZ              Dystrochrept,           (1677%)
                          sandy loam,
                          pH 5.7, OC 63
                          g/kg
                        Typic Hapludand, silt
                          loam, pH 4.9, OC
                          77 g/kg
Gupta et al. (1988),    Grey Luvisols,          Microbial S
  Canada                  pH 5.4 and 5.7,         (136-168%), acid
                          OC 11 and 34            phosphatase
                          g/kg                    (106-130%)
Gupta and Germida       Grey Luvisol,           Microbial S (178%),
  (1988); Gupta           pH 5.7, OC 28           acid phosphatase
  et al. (1988),          g/kg                    (141%)
  Canada
Ladd et al. (1994),     Red-brown earth,
  Australia               14% clay, pH 6.8,
                          OC 10 g/kg
Parfitt et al. (2005),  Typic Dystrudepts,      Microbial P
  NZ                      pH 5.6-6.0, OC          (168-300%),
                          32-11 t/ha in           microbial N
                          0-7.5 cm                (106-163%), total
                                                  nematodes
                                                  (123-223%)
Ryan et al. (2000),     Mostly red-brown
  Australia               earths, mean
                          pH 6.2, mean OC
                          2.6 g/kg
Moore et al. (2000),    Hapludoll, 22% clay
  USA                     and 31% sand,
                          mean pH 6.9,
                          mean OC 21 g/kg
                        Haplaquoll, 33%
                          clay and 24%
                          sand, mean
                          pH 6.2, mean OC
                          34 g/kg
Graham et al.           Chromic Vertisol,       microbial C
  (2002); Graham          58% clay, pH 5.8,       (119-136%),
  and Haynes 2005,        OC 42 g/kg              FDA hydrolysis
  S. Africa                                       rate, acid
                                                  phosphatase

Reference and           Soil type and           Other changes
location                characteristics (A)

Ryan and Ash            Red-brown earth,
  (1999), Australia       pH 6, OC 26 g/kg
Rubio et al. (2003),    Volcanic soil, pH 5.5,
  Chile                   18% SOM
Sarathchandra et al.    Not given
  (1993), NZ
                                                Pasture production
                                                  [up arrow]
Lovell and Hatch        36% clay
  (1997), UK
Lupwayi et al.          Gray Luvisols and
  (2001), Canada          Black
                          Chernozems,
                          pH 5.7 and 7.3,
                          OC 28 and 47
                          g/kg
Perrott et al. (1992),  Yellow-brown earth,     Herbage [up arrow]
  NZ                      silt loam, pH 5.8,
                          OC 76 g/kg
Sarathchandra et al.    Umbric                  OC [down arrow], pH
  (2001), NZ              Dystrochrept,           [down arrow] by 0.4
                          sandy loam,             units
                          pH 5.7, OC 63
                          g/kg
                        Typic Hapludand, silt
                          loam, pH 4.9, OC
                          77 g/kg
Gupta et al. (1988),    Grey Luvisols,          pH [down arrow] by
  Canada                  pH 5.4 and 5.7,         0.15 units
                          OC 11 and 34
                          g/kg
Gupta and Germida       Grey Luvisol,           pH [down arrow] by 1.0
  (1988); Gupta           pH 5.7, OC 28           units, OC [down
  et al. (1988),          g/kg                    arrow]
  Canada
Ladd et al. (1994),     Red-brown earth,        pH [down arrow] by
  Australia               14% clay, pH 6.8,       0.4-1.0 units
                          OC 10 g/kg
Parfitt et al. (2005),  Typic Dystrudepts,
  NZ                      pH 5.6-6.0, OC
                          32-11 t/ha in
                          0-7.5 cm
Ryan et al. (2000),     Mostly red-brown
  Australia               earths, mean
                          pH 6.2, mean OC
                          2.6 g/kg
Moore et al. (2000),    Hapludoll, 22% clay     pH [down arrow] by
  USA                     and 31% sand,           0.1-0.9 units;
                          mean pH 6.9,            microbial C
                          mean OC 21 g/kg         related to OC
                        Haplaquoll, 33%
                          clay and 24%
                          sand, mean
                          pH 6.2, mean OC
                          34 g/kg
Graham et al.           Chromic Vertisol,       OC [up arrow], pH [down
  (2002); Graham          58% clay, pH 5.8,       arrow] by 0.7 units
  and Haynes 2005,        OC 42 g/kg
  S. Africa

(A) Soil classification, texture, pH, and OC content as far as given.

(B) mg/kg soil.

Table 5. Comparative effects of inorganic and organic fertilisers on
soil organisms as concluded from field experiments

FYM, farmyard manure

Reference       Soil type and           Vegetation     Time frame
and location    characteristics (A)                     (years)

Peacock et al.  Typic Fragiudalf, silt  Maize-pasture      5
  (2001), USA   loam, pH 6.0, OC          rotation
                15 g/kg
Leita et al.    Calcic Cambisol,        Cover crop         12
  (1999),       29% clay, 47%
  Italy         sand, pH 7.8, OC
                7,9 g/kg
Witter et al.   35% clay, 21% sand,     Arable crops     34-36
  (1993),       pH 6.2, OC
  Sweden        10 g/kg
Dick et al.     Haploxeroll,            Wheat fallow       55
  (1988), USA   coarse-silty,             rotation
                pH 6.5
Parham et al.   Paleustoll, 23% clay,   Wheat              69
  (2002,        38% sand, pH 5,
  2003), USA    OC 6.7 g/kg
                                                          100
Colvan et al.   Clay loam, pH 5.2,      Pasture           100
  (2001);       OC 34 g/kg
  O'Donnell et
  al. (2001),
  UK
Houot and       Agrudalf, 22-30%        Wheat-sugar       112
  Chaussod      clay, 40-44%              beet
  (1995),       sand, pH 8.0-8.3
  France

Reference       Fertiliser          Negative
and location    (kg/ha.year)

Peacock et al.  18 N (AN)           Gram -ve bacteria
  (2001), USA                         (85%)
                FYM (252 N)
Leita et al.    100 N (AN), 75 P
  (1999),         (SP), 150 K (PS)
  Italy         Compost
                  (500-1500 N)
                FYM (500 N)
Witter et al.   80 N (CaN)
  (1993),       80N(AS)             Microbial C(13%)
  Sweden        FYM (4 t/ha.year)
                Sewage sludge       Microbial C (69%)
                  4 t/ha.year)
Dick et al.     90N                 Amidase, urease
                Straw + manure
Parham et al.   67 N, 15 P, 28 K    Fast-growing
  (2002,                              bacteria
  2003), USA
                FYM (269 N/ha.4
                  years
Colvan et al.   35 N (AS)           Microbial P, C
  (2001);       60 P
  O'Donnell et  67 K
  al. (2001),   35 N, 60 P, 67 K
  UK
                FYM (20 t/ha.year)
Houot and       87 N, 40 P, 75 K
  Chaussod      FYM (1 t/ha.year)
  (1995),
  France

                Effect on soil organisms
                (amount and activity; % of control)

Reference       No change             Positive
and location

Peacock et al.  Total PLFAs           Gram +ve bacteria
  (2001), USA                           (120%)
                Gram +ve              Total PLFAs
                  bacteria              (170%), Gram
                                        -ve bacteria
                                        (115%)
Leita et al.    Microbial C
  (1999),                             Microbial C
  Italy                                 (200-350%)
                                      Microbial C
                                        (243%)
Witter et al.                         Microbial C (142%)
  (1993),
  Sweden                              Microbial C
                                        (209%)
Dick et al.     Acid and alk.
  (1988), USA     phosphatase,
                  arylsulfatase,
                  glucosidase
                                      Acid and alk.
                                        phosphatase,
                                        arylsulfatase,
                                        glucosidase,
                                        amidase, urease
Parham et al.   Bacterial and fungal  Microbial C, acid
  (2002,          CFU, alk.             phosphatase,
  2003), USA      phosphatase,          slow-growing
                  phosphodiesterase,    bacteria
                  pyrophosphatase
                Fungal CFU, acid      Microbial C, alk.
                  phospbatase,          phosphatase,
                  fast-growing          phosphodiesterase,
                  bacteria              pyrophosphatase,
                                        bacterial CFU,
                                        slow-growing
                                        bacteria
Colvan et al.                         Phosphatase
  (2001);       Phosphatase           Microbial P
  O'Donnell et                        Phosphatase
  al. (2001),                         Microbial P,
  UK                                    phosphatase
                                      Microbial P,
                                        phosphatase
Houot and                             Microbial C
  Chaussod                            Microbial C
  (1995),
  France

                Other
Reference       changes
and location

Peacock et al.  pH [down arrow] by
  (2001), USA     0.6 units
                OC [up arrow]
Leita et al.    Microbial C
  (1999),         correlated to OC
Witter et al.   pH [down arrow] with
  (1993),         AS and sewage sludge;
  Sweden          microbial C and
                  respiration related
                  to OC
Dick et al.     pH [down arrow] by
  (1988), USA     0.6 units
                pH [up arrow] by 0.6
                  units, OC [down arrow]
Parham et al.   pH [down arrow] by
  (2002,          ~0.5 units
  2003), USA
                pH [up arrow] by
                  ~0.6 units
Colvan et al.   pH [down arrow] by
  (2001);         2 units
  O'Donnell et
  al. (2001),
  UK
                pH [up arrow] by
Houot and         0.6 units
  Chaussod      Microbial C related
  (1995),         to OC
  France

(A) Soil classification, texture, pH, and OC content as far as given.

Table 6. Intended benefits of organic amendments

Reason for organic amendment     Examples

(a) Supply bulk nutrients for    Animal manures, sewage sludge, and
    plant production               other composted organics supply N,
                                   P, K for plant uptake
(b) Increase availability of     Bacteria solubilise P and S from soil
    existing soil nutrients        minerals (Grayston and Germida 1991;
                                   Gyaneshwar et al. 2002). Mycorrhizae
                                   extend root exploration and uptake
                                   of immobile nutrients (Dodd and
                                   Thomson 1994)
(c) Increase the availability    Humic acid products may increase
    of applied fertilisers         fertiliser P availability (Delgado
                                   et al. 2002)
(d) Fix N from air               Symbiotic and free-living [N.sub.2]-
                                   fixing bacteria (Brockwell 2004;
                                   Kennedy et al. 2004)
(e) Improve soil chemical        Manure, sewage sludge, and compost can
    fertility                      increase soil organic matter and
                                   cation exchange capacity. Humic
                                   substances can enhance micronutrient
                                   availability (Chen et al. 2004)
(f) Improve soil physical        Mulches prevent erosion and improve
    condition                      water infiltration and water
                                   storage (Buerkert et al. 2000).
                                   Manures and mycorrhizae enhance
                                   aggregate stability and pore
                                   structure (Tisdall and Oades 1982)
(g) Improve soil biology         Manures and composts can add
                                   significant quantities of readily
                                   decomposable C substrate for
                                   microbes, and add microbes as well
                                   (Semple et al. 2001). 'Helper'
                                   bacteria can stimulate mycorrhizal
                                   and rhizobial symbioses (Garbaye
                                   1994)
(h) Plant growth promoters       Rhizobacteria and possibly humic
                                   substances can supply plant
                                   growth-promoting hormones (Bowen and
                                   Rovira 1999)
(i) Direct suppression of        Composted manure and brewed compost
    plant disease                  leachates may suppress plant
                                   diseases (Scheuerell and Mahaffee
                                   2002). Mycorrhizal fungi can control
                                   nematodes and root diseases
                                   (Siddiqui and Mahmood 1995; Whipps
                                   2004)
(j) Indirect suppression of      Rhizobacteria can be added to seed or
    plant disease                  soil to enhance plant resistance to
                                   disease. Organic substrates may
                                   stimulate plant-beneficial microbial
                                   populations
(k) Decontaminate polluted       Microbially catalysed reactions in
    soils                          soil can breakdown organic
                                   pollutants or precipitate metals
                                   making them unavailable for plant
                                   uptake or water transport
                                   (Romantschuk et al. 2000)
(l) Degrade crop residues and    Microbial inoculants may enhance
    other compostable              breakdown of crop residues and waxes
    materials                      that cause water repellency
                                   (Damodaran et al. 2004; Roper 2004)

Table 7. Effects of animal manures, biosolids,
and composts on soil organisms

Reference and location   Soil type and           Compared treatments
                         characteristics

Trochoulias et al.       Red basaltic soil       Poultry manure,
  (1986), Australia                                gypsum + dolomite,
                                                   others
Poll et al. (2003),      Luvic Phaeozem (FAO),   Long-term annual
  Germany                  8% clay, 72% sand,      application of
                           pH 5.6, OC 10 g/kg      farmyard manure,
                                                   control
Dinesh et al. (2000),    5 soils; pH 5.7-6.4,    3 years poultry
  India                    OC 6-9 g/kg             manure, FYM,
                                                   sesbania and
                                                   gliricidia residues,
                                                   control
Wu et al. (2004),        3 soils: Calcaric       Manure, mineral
  China                    Cambisols, Haplic       fertiliser,combined
                           Greyxems, and           manure and
                           Calcic Kastanozems      fertiliser
                           (FAO); 25-30% clay,
                           pH 8.3-8.4, OC
                           7-17 g/kg
Min et al. (2003),       Mesiq Achic             5 years of dairy
  USA                      Hapludult, fine         manure slurry,
                           loamy, pH 6.6, OC       mineral fertiliser,
                           15.8 g/kg               control
Thomsen et al. (2003),   3 soils: 11-34% clay,   Lab. incubation of
  Denmark                  11% sand, pH            soil amended with
                           6.4-7.4, OC             sheep manure at
                           13.7-15.4 g/kg          various soil matric
                                                   potentials and clay
                                                   contents
Yang et al. (2003),      Thermic Typic           Surface mulches of
  USA                      Xerothent; coarse       grass clippings,
                           loam; pH 8.1, OC        lucerne stems,
                           2 g/kg                  composted manure,
                                                   eucalyptus, oleander
                                                   or pine chip waste,
                                                   chipped
                                                   construction waste
Villar et al. (2004),    3 Typic Haplumbrepts;   Single application of
  Spain                    sandy loam to           poultry manure, NPK
                           sandy clay loam;        fertiliser to soil
                           pH 4.6-6.3; OC          after wildfire
                           7.1-19.9 g/kg
Baker et al. (2002),     3 soils: Aeric          Biosolids (30120 t/ha)
  Australia                Kandiaqualf, Typic
                           Natraqualf, Oxic
                           Ustropept
Munn et al. (2001),      6 soils: 6-54% clay,    Single application of
  Australia                pH 4.2-6.4, OC          biosolids from 5
                           7-32 g/kg               treatment plants
                                                   applied to one soil.
                                                   Biosolids from 1
                                                   plant applied to 6
                                                   soils
Abaye et al. (2005),     Typic Udipsamment;      Long-term FYM,
  England                  sandy loam; 8%          metal-contaminated
                           clay; pH 6.5-7.1;       sewage sludge, NPK
                           OC 5.2-14.8 g/kg        mineral fertiliser
Chaudhuri et al.         Acid lateritic soil;    Several combinations
  (2003), India            pH 5.2; OC 5.4 g/kg     of sludge and coal
                                                   ash, control, NPK
                                                   fertiliser
Usman et al. (2004),     Calcareous soil;        Short-term incubation,
  Germany                  3.5% clay, 87%          sewage sludge,
                           sand; pH 8.16; OC       composted turf and
                           3.1 g/kg                plant residues
Alvarez et al. (1999),   Thermic Vertic          2 years of sewage
  Argentina                Argiudol; clay          sludge applied to
                           42%, sand 14%; pH       de-surfaced soils
                           5.8; OC 17 g/kg
Barbarick et al.         2 soils: Aridic         Single application of
  (2004), USA              Argiboroll, Aridic      biosolids
                           Argiustoll; pH 7.3,
                           5.9; OC 1.5 g/kg
Garcia Gil et al.        Calcareous sandy        Single application of
  (2004), Spain            loam; sand 41%,         sewage sludge
                           clay 29%; pH 8.1;
                           OC 10.1 g/kg
Speir et al. (2003),     Typic Udipsamment;      Compost of biosolids,
  New Zealand              coarse sand; pH         wood waste
                           6.1; OC 39 g/kg         and green waste
Canali et al. (2004),    Sandy loam; pH 7.8;     Composts of distillery
  Italy                    OC 17.3 g/kg            waste and livestock
                                                   manure, poultry
                                                   manure, mineral
                                                   fertiliser control
Wells et al. (2000),     Luvic Ferrasol          Composts of woody
  Australia                (yellow earth); 77%     material with either
                           sand, 15% clay; pH      manure (poultry and
                           5.4; OC 11.9 g/kg       horse) or sewage
                                                   sludge, several
                                                   mineral fertiliser
                                                   treatments
Franco et al. (2004),    10 soils: 4             Glucose, maize stalks,
  Italy                    Inceptisols, 3          or maize stalk
                           Mollisols, 3            compost added to
                           Entisols; 10-60%        soils contaminated
                           clay; pH 5.2-8.3;       with crude oil
                           OC 13.6-58.5 g/kg
Lalande et al. (2003),   Orthic Humo-Ferric      Single application of
  Canada                   Podzol; loamy           co-composted
                           sand; pH 5.4; OC        papermill sludge
                           26-35 g/kg              and hog manure
                                                   applied alone or in
                                                   combination with
                                                   mineral fertilisers
Zaller and Kopke         Fluvisol; pH 5.35       9-year study of
  (2004), Germany                                  traditionally
                                                   composted FYM, 2
                                                   types of
                                                   biodynamically
                                                   composted manure
Miyittah and             Typic Hapludand; pH     Composts of soymilk
  Inubushi (2003),         4.87; OC 64.9 g/kg      residues, cow
  Japan                                            manure, poultry
                                                   manure, and sewage
                                                   sludge
Tiquia et al. (2002),    Silt loam; 29% sand,    Soil mulched with
  USA                      29% clay; pH 5.5;       composted yard
                           OC 29 g/kg              waste, ground wood
                                                   pallets, bare soil
                                                   control, with or
                                                   without chemical
                                                   fertiliser

Reference and location   Effects

Trochoulias et al.       Manured treatment had highest
  (1986), Australia        microbial C

Poll et al. (2003),      Manure addition enhanced
  Germany                  microbial biomass and xylanase
                           and invertase activity
Dinesh et al. (2000),    Organic manures increased
  India                    microbial biomass, activity,
                           diversity, and C turnover
Wu et al. (2004),        Manure [+ or -] N and P fertiliser
  China                    treatments restored OC and
                           microbial C to the level of the
                           native sod
Min et al. (2003),       Dairy manure slurries increased OC
  USA                      and microbial biomass and
                           decreased metabolic quotient
                           compared with mineral fertiliser
                           treatments
Thomsen et al. (2003),   Manure increased soil respiration in
  Denmark                  all combinations of soils and
                           matric potentials. Microbial
                           biomass increased most with the
                           addition of manure to the
                           sandiest soil
Yang et al. (2003),      Only grass clippings stimulated
  USA                      dehydrogenase activity in the
                           soil measured after 1 year.
                           Eucalyptus yardwaste and grass
                           clippings caused shifts in
                           bacterial populations and
                           increased bacterial diversity but
                           only at the soil surface
Villar et al. (2004),    Poultry manure application
  Spain                    increased microbial biomass C,
                           particularly at high dose. Little
                           or no changes as a consequence
                           of inorganic fertilisation
Baker et al. (2002),     Increase in earthworm abundance
  Australia
Munn et al. (2001),      Symbiotic effectiveness of
  Australia                rhizobium dependent on soil
                           type and level and source of
                           biosolids, not on basis of heavy
                           metal concentrations
Abaye et al. (2005),     Microbial biomass-C and total
  England                  bacterial numbers greater in the
                           FYM-treated soil than in NPK
                           and sludge-amended soils.
                           Relatively small heavy-metal
                           concentrations decreased
                           microbial C and bacterial
                           numbers, increased metabolic
                           quotient, and changed microbial
                           community 40 years after metal
                           inputs ceased
Chaudhuri et al.         Microbial C and soil enzyme
  (2003), India            activities increased with all
                           amendments; highest at equal
                           proportions of coal ash and
                           sludge. Mobile fractions of Cd
                           and Ni correlated with
                           microbial C
Usman et al. (2004),     Compared with compost, sewage
  Germany                  sludge caused greater increases
                           in soil respiration, microbial C,
                           and metabolic quotient,
                           especially with increasing
                           application rate
Alvarez et al. (1999),   Microbial biomass not affected by
  Argentina                sludge, but metabolic activity
                           and organic matter
                           mineralisation enhanced.
                           Increased soil respiration from
                           sludge-amended soil represented
                           21% of C applied that year and
                           15% of C applied the year before
Barbarick et al.         6 years after application, amended
  (2004), USA              plots had increased microbial
                           respiration, nitrogen
                           mineralisation, root colonisation
                           by AM, microbial biomass. No
                           change in metabolic quotient
Garcia Gil et al.        Microbial biomass, basal
  (2004), Spain            respiration, metabolic quotient,
                           and enzymatic activities
                           increased in soil 9 months after
                           sludge application, but increases
                           had disappeared after 36 months,
                           presumably due to the loss of
                           energy sources
Speir et al. (2003),     Soil basal respiration, microbial C,
  New Zealand              and anaerobically mineralisable
                           N were significantly increased in
                           the amended plots. No effects on
                           rhizobial numbers or microbial
                           biosensors (Rhizotox C and
                           lux-marked Escherichia coli)
Canali et al. (2004),    Parameters related to potentially
  Italy                    mineralisable C showed
                           significant differences among the
                           treatments. No differences were
                           observed in biodiversity indexes
Wells et al. (2000),     Both composted treatments higher
  Australia                in microbial C than mineral
                           fertiliser treatments, but trial was
                           of systems so there were also
                           other differing factors
Franco et al. (2004),    The addition of organic substrates
  Italy                    (glucose, maize stalks, and maize
                           stalk compost) to contaminated
                           soils had no synergistic effect on
                           the decomposition of crude oil
                           but produced a marked increase
                           in microbial biomass, although
                           the increase was smaller than in
                           uncontaminated soils. Compost
                           decreased the stress conditions
                           caused by oil contamination as
                           measured by a reduction in
                           metabolic quotient
Lalande et al. (2003),   Activities of [beta]-glucosidase,
  Canada                   [beta]-galactosidase, acid
                           phosphatase, urease, and
                           fluorescein diacetate hydrolysis,
                           microbial C and soil respiration
                           all increased compared with the
                           control. Addition of fertiliser to
                           compost resulted in a greater
                           increase in enzyme activities
                           than compost alone but had little
                           effect on microbial biomass.
                           Enzyme activities and microbial
                           biomass decreased in the second
                           season
Zaller and Kopke         FYM increased microbial biomass,
  (2004), Germany          dehydrogenase activity,
                           decomposition (cotton strips),
                           but not saccharase activity,
                           microbial basal respiration, or
                           metabolic quotient. Biodynamic
                           manure preparation decreased
                           soil microbial basal respiration
                           and metabolic quotient compared
                           to non-biodynamic manure.
                           After 100 days, decomposition
                           was faster in plots which
                           received biodynamic FYM than
                           in plots which received no or
                           non-biodynamic FYM
Miyittah and             Soil respiration increased rapidly
  Inubushi (2003),         initially, but patterns differed
  Japan                    among the composts. Composted
                           soymilk treatment gave higher
                           C[O.sub.2]-evolution and lower
                           metabolic quotient than the other
                           composts
Tiquia et al. (2002),    Microbial respiration rate was
  USA                      highest in soils mulched with
                           composted yard wastes.
                           Mulching with compost strongly
                           influenced the structure of the
                           microbial rhizosphere
                           community

Table 8. Impact of herbicides on non-target soil organisms

Reference and            Soil type and             Active chemical
location                 characteristics

Sannino and Gianfreda    22 soils from Campania        Atrazine
  (2001), Italy            region, sandy to clayey
                           soils, OC 1.2-34.2 g/kg
Seghers et al. (2003),   Soils from a field site in    Atrazine,
  Belgium                  Melle, Belgium. No            metolachlor
                           further descriptions
Panda and Sabo (2004),   Soil from upland non-         Butachlor
  India                    irrigated paddy field.
                           Sandy-loam with pH 6.8,
                           OM 2.7%
Araujo et al. (2003),    Two Brazilian soils: sandy    Glyphosate
  Brazil                   clay, pH 5.9, OM 2.3%,
                           and clay soil, pH 5.2,
                           OM 2%
Busse et al. (2001),     Three soils: 18-34% clay,     Glyphosate
  USA (forestry)         pH 5.4-5.9, OM 2.0-6.7%
Sannino and Gianfreda    Described above               Glyphosate,
  (2001), Italy                                          paraquat
Dalby et al. (1995),     Yellow, duplex loam           Glyphosate and
  Australia                (Palexeralf)                  2,4-DB
Reid et al. (2005), UK   Three soils: Icknield         Isoproturon
                           (silty clay loam, OM
                           4.8%), Shellingford
                           (sandy loam, OM 4.3%) and
                           Evesham (clay, OM 6.0%)
Mosleh et al. (2003),    43.9% clay, 28.7% sand, pH    Isoproturon
  France                   8.16, OC 7.7%
Das et al. (2003),       Clayey Typic Fluvaquent,      Oxyfluorfen,
  India                    pH 7.1, OC 5.8%               oxadiazon
Strandberg and           Review paper covering         Pendimethalin
  Scott-Fordsmand          several soil types
  (2004), Denmark
Amorim et al. (2005),    OECD standard soil: pH 6,     Phenmedipham
  OECD standard soil       OM 8%. 17 other test
  and several European     soils: pH 3.2-6.9, OM
  test soils               1.7-15.9%
Heupel (2002),           Laboratory standard soil      Phenmedipham
  Germany: standard        described as a loamy sand
  soil
Kinney et al. (2005),    Remmit fine sandy loam        Prosulfuron
  USA                      (Ustollic camborthids)

Reference and            Effects
location

Sannino and Gianfreda    Significant activation of soil urease
  (2001), Italy            activity (up to 100-fold
                           increase), and suppression of
                           invertase enzyme
Seghers et al. (2003),   Altered community structure of
  Belgium                  several groups of bacteria and
                           actinomycetes
Panda and Sabo (2004),   Very toxic, suppressing growth,
  India                    sexual maturation and cocoon
                           production of the earthworm
                           Drawida willsi following single
                           dose at recommended rate
Araujo et al. (2003),    Bacteria reduced. Fungi and
  Brazil                   actinomycetes increased.
                           Microbial activity increase by
                           9-19%. Increased glyphosate
                           degradation with repeated
                           application
Busse et al. (2001),     Short term changes to community
  USA (forestry)           structure. Increased microbial
                           activity and no long-term
                           changes to community structure
Sannino and Gianfreda    Activation of urease and invertase
  (2001), Italy            soil enzymes, but glyphosate
                           suppressed phosphatase activity
                           (up to 98%)
Dalby et al. (1995),     No effect of single dose to soil on
  Australia                growth or survival of the
                           earthworms Aporrectodea
                           trapezoides, A. caliginosa,
                           A. longa or A. rosea
Reid et al. (2005), UK   Catabolic activity induced in soils
                           not previously treated with this
                           herbicide
Mosleh et al. (2003),    Affected earthworms at very high
  France                   soil concentrations (not
                           agricultural rates) with LC50 for
                           Eisenia fetida > 1000 mg/kg
Das et al. (2003),       Both herbicides stimulated
  India                    microbial populations, and
                           increased availability of
                           phosphorus in rhizosphere soil
                           of rice
Strandberg and           Soil nematodes and other
  Scott-Fordsmand          invertebrates reduced,
  (2004), Denmark          plant-rhizobium symbiosis
                           reduced at herbicide rates as low
                           as 0.5-1.0 kg/ha
Amorim et al. (2005),    Enchytraeid worms avoided these
  OECD standard soil       chemicals in standard avoidance
  and several European     test procedures. In some soil
  test soils               types, avoidance behaviour
                           exhibited at low concentrations
                           (1 mg/kg)
Heupel (2002),           Dose-dependent avoidance of the
  Germany: standard        collembolan Isotoma anglicana,
  soil                     Heteromurus nitidus,
                           Lepidocyrtus violaceus,
                           Folsomia candida, and
                           Onychiurus armatus
Kinney et al. (2005),    Significant reduction in production
  USA                      of [N.sub.2]O and NO following
                           N-based fertiliser application:
                           significant reduction in
                           nitrification

Table 9. Impact of insecticides and nematicides
on non-target soil organisms

Reference and            Soil type and        Active chemical
location                 characteristics

Hart and Brookes         Silty clay loam,     Aldicarb, chlorfenvinphos
  (1996), UK               pH 6.4, OC 13.6
                           g/kg
Van Zwieten et al.       Sand, sandy clay     Arsenic
  (2003), Australia        loam and clay
  (contaminated site)      loam soils. No
                           further details
Ghosh et al. (2004),     Range of clay loam   Arsenic
  India                    to clay soils,
                           pH 6.9-7.5, OC
                           8.7-10.7%
Amorim et al. (2005),    Described            Benomyl
  OECD standard soil       previously
  and several European
  test soils
Ribera et al. (2001),    OECD artificial      Carbaryl
  France: OECD             soil was
  standard soil            prepared
Sannino and Gianfreda    Described            Carbaryl
  (2001), Italy            previously
Kanungo et al. (1998)    Typic Haplaquept     Carbofuran
                           (deltaic
                           alluvium), pH
                           6.7, OM 17%
Panda and Sahu (2004),   Described            Carbofuran, malathion
  India                    previously
Pandey and Singh         Sandy loam,          Chlorpyrifos, quinalphos
  (2004), India            pH 6.75, OC
                           0.49%
 Menon et al. (2005),     Loamy sand, pH       Chlorpyrifos, quinalphos
  India                    8.2, and sandy
                           loam, pH 7.7,
                           both soils from
                           semi-arid
                           regions
Endlweber et al.         No data on soil      Chlorpyrifos, dimethoate
  (2005), Germany          types provided
Edvantoro et al.         11 soils, sandy to   DDT, arsenic
  (2003), Australia        clayey, pH           contamination
  (contaminated site)      4.9-6.0, OC
                           0.14-5.2%
Megharaj et al. (2000),  Sandy soil, pH       DDT
  Australia                7.1, OC
  (contaminated site)      1.77-3.6%
Singh and Singh          Silty sand, pH       Diazinon
  (2005), India            6.98-7.22,
                           OM 0.63-0.93%
Martikainen et al.       Soil from a          Dimethoate
  (1998), Finland          pesticide free
                           grain field in
                           central Finland,
                           no further
                           description
Dalby et al. (1995),     Described            Dimethoate
  Australia                previously
Singh and Singh          Described            Imidacloprid
  (2005), India            previously
Capowiez and Berard      Artificial soil      Imidacloprid
  (2006), France           with pH 8.3
Singh and Singh          Described            Lindane
  (2005), India            previously
Loureiro et al.          Silty sand, pH       Lindane, dimethoate
  (2005), Portugal         5.03, OM 1.28%.
                           Also soils from
                           metal
                           contaminated
                           mine site,
                           pH 4.14-4.47,
                           OM 2.88-5.07%
Panda and Sahu           Sandy loam, pH       Malathion
  (1999), India            6.8, OM 2.7%

Reference and            Effects
location

Hart and Brookes         Aldicarb caused a long-term
  (1996), UK               increase of 7-16% in
                           microbial C. No other effects
                           found on respiration or N
                           mineralisation
Van Zwieten et al.       Arsenic co-contamination was
  (2003), Australia        shown to inhibit the
  (contaminated site)      breakdown of DDT, and a
                           concomitant reduction in
                           microbial activity was found
Ghosh et al. (2004),     Arsenic between 11-36 mg/kg
  India                    in soil reduced microbial
                           biomass, respiration,
                           fluorescein diacetate
                           hydrolysis and
                           dehydrogenase activity, and
                           induced microbial stress
                           measured by increased
                           metabolic quotient
Amorim et al. (2005),    Enchytraeid worms avoids
  OECD standard soil       benomyl in standard
  and several European     avoidance test procedures
  test soils
Ribera et al. (2001),    Significant reductions in
  France: OECD             acetylcholinesterase and
  standard soil            other biotransformation
                           enzymes in earthworms
Sannino and Gianfreda    Activation of urease and
  (2001), Italy            invertase soil enzymes, but
                           suppression of phosphatase
                           enzyme
Kanungo et al. (1998)    Appears to have an inhibitory
                           effect on nitrogenase activity
                           in Azospirillum sp. at higher
                           application rates
Panda and Sahu (2004),   Significant reduction in
  India                    acetylcholinesterase activity
                           in earthworms (D. willsi) for
                           up to 45 days (carbofuran)
                           and 75 days (malathion)
Pandey and Singh         Reduced bacterial numbers, but
  (2004), India            significantly increased
                           fungal numbers with
                           chlorpyrifos and slightly
                           reduced fungal numbers
                           (short-term) with quinalphos
Menon et al. (2005),     Reduced oxidative capability of
  India                    the soils as measured by
                           reduced dehydrogenase
                           activity and inhibited iron
                           reduction
Endlweber et al.         Chlorpyrifos reduced
  (2005), Germany          collembolan density to a
                           greater extent than
                           dimethoate. Both changed
                           the dominance structure of
                           the collembolan community,
                           but had no effects on species
                           composition
Edvantoro et al.         Bacterial and fungal numbers,
  (2003), Australia        and biomass carbon were
  (contaminated site)      reduced in contaminated
                           soils compared to controls
Megharaj et al. (2000),  Reduced bacterial and soil algal
  Australia                populations, but may have
  (contaminated site)      increased fungal counts
Singh and Singh          Significant increase in
  (2005), India            dehydrogenase activity and
                           decrease in alkaline
                           phosphomonoesterase for up
                           to 30 days following
                           treatment
Martikainen et al.       Short term reduction in
  (1998), Finland          microarthropod numbers
                           (Collembola), but recovery
                           in numbers after time.
                           Community structure
                           remained differentiated.
                           Slight reduction in soil
                           microbial biomass
                           (measured by ATP)
Dalby et al. (1995),     Single dose on soil had no
  Australia                measured effect on the
                           growth or survival of the
                           earthworms Aporrectodea
                           trapezoides, A. caliginosa,
                           A. longa, or A. rosea
Singh and Singh          Significant increases in
  (2005), India            dehydrogenase and
                           phosphomonoesterase
                           activities when used as seed
                           dressing, effect lasting up to
                           60 days
Capowiez and Berard      Significantly reduced
  (2006), France           burrowing activity in two
                           earthworm species at
                           sub-lethal concentrations
                           (0.5-1 mg/kg), but no
                           avoidance of the insecticide
Singh and Singh          Significant decreases in both
  (2005), India            dehydrogenase and
                           phosphomonoesterase
                           enzyme activities for up to
                           90 days
Loureiro et al.          Collembola avoid soil with
  (2005), Portugal         lindane (10-20 mg/kg) and
                           dimethoate (5-20 mg/kg),
                           while earthworms avoided
                           dimethoate at 2.5 mg/kg
Panda and Sahu           Short-term impacts of standard
  (1999), India            application rates of
                           malathion on earthworm
                           reproduction lasting for 105
                           days

Table 10. Impact of fungicides on non-target soil organisms

Reference and location   Soil type and                 Active
                         characteristics               chemical

Chen et al. (2001),      Silt-loam Luvisol, pH 6.3,    Benomyl
  USA                      OM 4%
Smith et al. (2000),
  USA                    Smectitic silt loam soil      Benomyl
Loureiro et al.
  (2005), Portugal
Martikainen et al.       Previously described          Benomyl
   (1998), Finland
                         Previously described          Benomyl
Hart and Brookes         Silty clay loam, pH 6.9,      Benomyl,
  (1996), UK             OC 1.36%                        triadimefon
Chen et al. (2001),      Previously described          Captan
  USA
Hu et al. (1995), USA    A well-drained sandy clay     Captan
                           loam, OC 0.8%
Van Zwieten et al.       Ferrosols with kaolinitic     Copper
  (2004), Australia        clay minerals. pH
  (field and OECD          6.3-6.8, OC 4.9-7.1%
  soil)
Merrington et al.        Ferrosols with kaolinitic     Copper
  (2002), Australia        clay minerals. pH
                           4.5-6.0, OC 4.88-8.82%
Loureiro et al.          Previously described          Copper,
  (2005), Portugal                                       carbendazim
Gaw et al. (2003,        Mainly silty soils, pH        Copper
  2006), New Zealand       5.3-6.3, OC 1.5-9.4%
Belotti (1998),          Loamy to clayey soils,        Copper
  Germany                  pH 5.5-7.2, OM 3.1-7.4%
Eijsackers et al.        Clayey soils, pH 5.7-6.8,     Copper
  (2005), South Africa     OM 0.6-1.3%
Chen et al. (2001),      Previously described          Chlorothalonil
  USA
Kinney et al. (2005),    Previously described          Mancozeb,
  USA                                                    chlorothalonil
Fravel et al. (2005),    In vitro studies not using    Chlorothalonil,
  USA                      soil                          azoxystrobin
Monkiedje et al.         Silty clay soil, pH 7.2, OC   Metalaxyl,
  (2002), Germany          1.69%                         mefenoxam

Reference and location   Effects

Chen et al. (2001),      Suppression of respiration, stimulation of
  USA                      dehydrogenase, effects were less
                           noticeable with organic matter addition
Smith et al. (2000),     Significant long-term effects on
  USA                      mycorrhizal colonization (80%
                           reduction), reduction in fungal to
                           bacterial ratios and nematode numbers
Loureiro et al.          Earthworms avoid benomyl at 1 mg/kg soil
  (2005), Portugal
Martikainen et al.       Total numbers of enchytraeids and
   (1998), Finland         nematodes, soil respiration and mineral
                           N were not affected, but the collembolan
                           community structure was affected
Hart and Brookes         Microbial biomass, SIR and mineralization
  (1996), UK               of soil organic N to ammonium and then
                           nitrate mostly unaffected by the
                           pesticide treatments
Chen et al. (2001),      Suppression of respiration and
  USA                      dehydrogenase; increases in
                           ammonium N
Hu et al. (1995), USA    Fungal length and density, and microbial C
                           and N significantly reduced
Van Zwieten et al.       Earthworm populations avoid soils with
  (2004), Australia        concentrations as low as 34 mg/kg. Lack
  (field and OECD          of breakdown of organic carbon suggest
  soil)                    potential long-term implications
Merrington et al.        Increased metabolic quotient indicating
  (2002), Australia        microbial stress at 280-340 mg Cu/kg.
                           Significantly reduced microbial biomass
                           and ratio of microbial biomass to OC
Loureiro et al.          Earthworm avoidance at concentrations
  (2005), Portugal         > 100 mg/kg. Test collembolan species
                           far less sensitive to copper. Carbendazim
                           avoidance by earthworms at 10 mg/kg
Gaw et al. (2003,        Reduced performance of soil functions
  2006), New Zealand       resulting in reduction of DDT
                           degradation
Belotti (1998),          Bioavailable copper concentration of
  Germany                  0.677 mg Cu/kg soil established as the
                           critical concentration for soil
                           impairment (irrespective of OC content)
Eijsackers et al.        Increasing copper resulted in reduced
  (2005), South Africa     burrowing of earthworms and decreased
                           growth of earthworms, resulting in
                           increased soil bulk densities in a
                           vineyard
Chen et al. (2001),      Suppression of respiration, stimulation of
  USA                      dehydrogenase
Kinney et al. (2005),    Significant reduction in production of [N.
  USA                      sub.2]O and NO following N-based fertiliser
                           application: Significant reduction in
                           nitrification
Fravel et al. (2005),    Both fungicides toxic to the biocontrol
  USA                      agent Fusarium oxysporum strain CS-20
                           which has been used to reduce incidence
                           of Fusarium wilt
Monkiedje et al.         Reduced enzyme activity, in particular
  (2002), Germany          dehydrogenase, for up to 90 days.
                           Increased bacterial numbers with
                           increasing doses, but toxic to N fixers at
                           1 mg/kg (mefenoxam) and 2 mg/kg
                           (metalaxyl)

Table 11. Impact of veterinary health products, fumigants, and other
biological and non-chemical plant protection measures on non-target
soil organisms

Reference and            Soil type and        Active chemical
location                 characteristics

                         Veterinary health products

Svendsen et al.          OECD standard soil   Ivermectin, fenbendazole
  (2005), Denmark          substrate
Jensen et al. (2003),    Sandy-loamy soil,    Tiamulin, olanquindox,
  Denmark                  pH 6.2, OC 1.6%    metronidazole, ivermectin
Radl et al. (2005),      Marine sediments,    Trenbolone (TBOH) from
  Germany                  78% <0.01 mm,        cattle production
                           pH 7.5, redox
                           21 mV
Vaclavik et al.          Sandy loam, pH       Tylosin, oxytetracycline,
  (2004), Denmark          6.1, OC 1.6%         sulfachloropyridazine
Westergaard et al.       Sandy soil, pH       Tylosin
  (2001), Denmark          6.8, OC 1.2%

                                    Fumigants

Massicotte et al.        Gravelly sandy       Chloropicrin
  (1998), USA              loam, no
                           further
                           descriptions
Ingham and Thies         Gravelly sandy       Chloropicrin
  (1996), USA              loam, no further
                           descriptions
Spokas et al. (2005),    Sandy soil, pH       Methyl isothiocyanate,
  USA                      5.0-6.0, OC        chloropicrin
                           1.11-1.39%
Karpouzas et al.         Silty sand, pH       Metham sodium, methyl
  (2005), Greece           7.2-7.5, OM          bromide
                           3.74-6.6%
Dungan et al. (2003),    Sandy loam, pH       Propargyl bromide, 1,3
  USA                      7.2, OM 0.92%      dichloropropene
Klose and Ajwa           Two sandy loam       Propargyl bromide,
  (2004), USA              soils, pH            InLine, Midas,
                           7.75-7.82,           Chloropicrin
                           OC 0.6-0.7%

                         Biological and non-chemical products

Cohen et al. (2005),     Clay loam soil,      Brassica napus seed meal
  USA                      pH 7.4
Cortet et al. (2006),    Three soils: silty   Bt toxin
  Denmark and France       sand, pH 6.2,
                           OM 6.4%; silty
                           clay, pH 8.1, OM
                           4.8%; clayey
                           silt, pH 8.2,
                           OM 1.5%
Accinelli et al.         Two soils: a loam,   Bt toxin
  (2004), Italy            pH 7.9, OC
                           0.92%; sandy
                           loam, pH 8.1,
                           OC 0.7%
Gelsomino and Cacco      A clay loam soil,    Solarisation with
  (2006), Italy            pH 7.2, OC 1.49%     transparent
                                                polyethylene film

Patricio et al.          A fertile peat,      Solarisation
  (2006), Brazil           pH 5.9, OM
                           around 20%

Reference and            Effects
location

                         Veterinary health products

Svendsen et al.          It was concluded that earthworm
  (2005), Denmark          populations will not be affected in the
                           field following normal use of these
                           products
Jensen et al. (2003),    Threshold values for toxicity (10%
  Denmark                  reduced reproduction or EC 10 values)
                           of antibacterials tiamulin, olanquindox
                           and metronidazole were in the range of
                           61-111 mg/kg soil for springtails and
                           83-722 mg/kg soil for enchytraeids.
                           Ivermectin more toxic with EC 10 values
                           of 0.26 mg/kg soil for springtails and
                           14 mg/kg soil for enchytraeids
Radl et al. (2005),      N-acetyl-glucosaminidase activity was
  Germany                  almost 50% lower in sediments
                           receiving trace quantities of TBOH.
                           Biolog substrate utilisation was
                           reduced, and this appeared to be
                           permanent
Vaclavik et al.          Tylosin and sulfachloropyridazine
  (2004), Denmark          significantly impact on gram positive
                           bacteria, while oxytetracycline inhibits
                           general microbial respiration at levels as
                           low as lmg/kg soil

Westergaard et al.       Long term changes to microbial
  (2001), Denmark          community structure, and short term
                          reduction in total microbial numbers

                                    Fumigants

Massicotte et al.        Chloropicrin did not adversely affect the
  (1998), USA              formation of ectomycorrhizae on young
                           Douglas fir seedlings by naturally
                           occurring fungi for up to 5 years
                           following treatment
Ingham and Thies         Limited effects on fungal biomass and
  (1996), USA              amoebae were found, but no major
                           impact on the soil food web
Spokas et al. (2005),    Altered soil biology leading to
  USA                      10-100-fold increases in N20
                           production lasting >48 days. No effects
                           on methane production. Methyl
                           isothiocyanate suppressed soil
                           respiration in laboratory trials
Karpouzas et al.         Inhibited degradation of an
  (2005), Greece           organophosphate nematicide applied to
                           soil 9 months following fumigation,
                           suggesting long term impacts
Dungan et al. (2003),    Significant decline in dehydrogenase
  USA                      activity; however, this recovered after
                           8 weeks in manure amended soil.
                           Bacterial community diversity
                           decreased with increasing fumigant
                           concentration
Klose and Ajwa           Organic matter turnover and nutrient
  (2004), USA              cycling, and thus, the long-term
                           productivity largely unaffected in soils
                           repeatedly fumigated with these
                           products, except for a reduction in
                           several key enzymes activities

                         Biological and non-chemical products

Cohen et al. (2005),     Reduced Rhizoctonia root infection and
  USA                      Pratylenchus spp nematodes. Suggested
                           mechanism was altered bacterial
                           community supporting nitrous oxide
                           production and induction of plant
                           systemic resistance
Cortet et al. (2006),    No effect on litter bag decomposition or N
  Denmark and France       mineralisation
Accinelli et al.         In laboratory studies, the presence of the
  (2004), Italy            Bt toxin inhibited the breakdown of
                           glufosinate-ammonium and glyphosate
Gelsomino and Cacco      Decreased bacterial diversity as measured
  (2006), Italy            by DGGE fingerprinting over time,
                           although short term increases in
                           diversity were noted
Patricio et al.          Reductions in microbial C, and fungal and
  (2006), Brazil         bacterial numbers, but no effect on
                         fluorescent pseudomonas
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Author:Bunemann, E.K.; Schwenke, G.D.; Van Zwieten, L.
Publication:Australian Journal of Soil Research
Geographic Code:8AUST
Date:Nov 1, 2006
Words:22304
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