Printer Friendly

Prospects of improving efficiency of fertiliser nitrogen in Australian agriculture: a review of enhanced efficiency fertilizers.

Abstract. Fertiliser nitrogen use in Australia has increased from 35 Gg N in 1961 to 972 Gg N in 2002, and most of the nitrogen is used for growing cereals. However, the nitrogen is not used efficiently, and wheat plants, for example, assimilated only 41% of the nitrogen applied. This review confirms that the efficiency of fertiliser nitrogen can be improved through management practices which increase the crop's ability to compete with loss processes. However, the results of the review suggest that management practices alone will not prevent all losses (e.g. by denitrification), and it may be necessary to use enhanced efficiency fertilisers, such as controlled release products, and urease and nitrification inhibitors, to obtain a marked improvement in efficiency. Some of these products (e.g. nitrification inhibitors) when used in Australian agriculture have increased yield or reduced nitrogen loss in irrigated wheat, maize and cotton, and flooded rice, but most of the information concerning the use of enhanced efficiency fertilisers to reduce nitrogen loss to the environment has come from other countries. The potential role of enhanced efficiency fertilisers to increase yield in the various agricultural industries and prevent contamination of the environment in Australia is discussed.

Additional keywords: controlled release, urease inhibitors, nitrification inhibitors, mitigation, greenhouse gases.

Introduction

As the intensity of agricultural production in Australia increases to keep pace with population growth, the need for food and fibre, and maintaining profit margin, fertiliser nitrogen use has increased from 35 Gg N in 1961 to 972 Gg N in 2002 (FAO 2007; Fig. 1). This fertiliser nitrogen is used mostly on cereals (702 Gg N), sugarcane, pasture, horticulture, cotton, and oilseeds. Rates of application varied from 2.5 to 229 kg N/ha (Table 1).

However, when fertiliser nitrogen is applied to soil it is not used efficiently, and the plant seldom assimilates >50% of the nitrogen added. Plant uptake for a range of crops and pastures in Australia varies from 6 to 59% of the nitrogen applied (Table 2). In general, bananas and flooded rice were the least efficient of the crops studied (6-17%). The mean recovery of applied nitrogen in Australian dryland wheat was 41% (22-59%), which is marginally better than the estimated worldwide efficiency of nitrogen for cereals of 33% (Raun and Johnson 1999).

One of the main reasons for the poor efficiency of fertiliser nitrogen use is that much of the nitrogen applied (up to 92%) can be lost from the plant-soil system (Table 3). Fertiliser nitrogen can be lost by ammonia volatilisation, during nitrification, and by leaching, erosion, runoff, and denitrification, and the relative importance of these processes can vary widely depending on the agroecosystem, fertiliser form, and method of application. For example, ammonia volatilisation was important when urea was applied to sugarcane fields covered with plant residues, while denitrification was the major loss process when anhydrous ammonia was drilled into irrigated cotton (Table 3). In most of the systems studied in Australia, erosion and runoff were controlled and leaching was small.

Lost nitrogen represents a serious economic loss to farmers, but the impact of the lost nitrogen on the environment and human health is equally, if not more, important. As pointed out above gaseous emissions of nitrogen via ammonia volatilisation, nitrification, and denitrification are the dominant mechanisms for the loss of fertiliser nitrogen from Australian agroecosystems. These processes result in the release of ammonia, nitric oxide, and the greenhouse gas nitrous oxide into the atmosphere. Agriculture is the main source of nitrous oxide in Australia, contributing 67 Gg in 2005 (AGO 2007); using IPCC (1997) guidelines it is calculated that 21 Gg of this comes from fertiliser nitrogen. In addition to the effect on global warming, the nitrogen gases produced from fertiliser can acidify soils, eutrophy lakes, rivers, and estuaries, decrease biodiversity in terrestrial ecosystems, affect atmospheric visibility, reduce the stratospheric ozone layer that protects the Earth from harmful ultraviolet radiation, and increase ozone concentrations in the troposphere with consequent health effects (Peoples et al. 2004).

Mitigation strategies aimed at reducing nitrogen loss are variable and can range from management practices through to the development of new technologies. New technologies include the use of products such as controlled release fertilisers and urease and nitrification inhibitors. Many of these products have been in some use for decades, with controlled release fertilisers commonly used in the nursery industry and inhibitors used for research purposes, yet their use in agricultural situations is relatively new and of particular interest in light of current concerns regarding greenhouse gas emissions.

[FIGURE 1 OMITTED]

The objective of this paper is to provide a review of the current literature on improving the efficacy of nitrogen fertilisers through the use of controlled release coatings and urease and nitrification inhibitors, concentrating specifically on work carried out in Australia.

Approaches to improve efficiency

The processes that generate nitrogen loss from soil are controlled directly by factors such as nitrogen availability and moisture, and indirectly by environmental or management factors (Granli and Bockman 1994). Some of the factors that control loss such as soil type, rainfall, radiation, and temperature are outside the farmer's control, but there are others that the farmer can influence. These manageable factors include fertiliser type, amount, method and time of application, water status (controlled by irrigation and drainage), soil pH (adjusted by application of lime), and soil compaction (tillage and trafficking).

In general, nitrogen loss can be decreased by management practices which increase the crop's ability to compete with the loss processes (Minami 1997). The approaches that have been suggested for improving the efficiency of fertiliser nitrogen include the following:

(i) using soil and plant testing to make best use of indigenous nitrogen (Johnkutty and Palaniappan 1996; Dobermann and Cassman 2004);

(ii) using the optimal form, rate, method and time of application of the fertiliser (Strong et al. 1992; Smith et al. 1997);

(iii) incorporation or deep placement of fertiliser (De Datta et al. 1989; Cai et al. 2002; Roy and Hammond 2004);

(iv) using split applications--several applications of small amounts of fertiliser during the growing season are more effective than one large dose at the beginning of the season (Hooper 2004);

(v) minimising application in the wet season to reduce leaching and denitrification (McTaggart et al. 1994);

(vi) delaying the supply of fertiliser until a substantial canopy has developed (Humphreys et al. 1988),

(vii) using foliar application (Smith et al. 1991); and

(viii) using inter seasonal cover crops to minimise the accumulation of nitrate during fallow periods (McLenaghen et al. 1996; Wagner-Riddle and Thurtell 1998; Cameron et al. 2002).

Where denitrification is likely to be the main process responsible for nitrogen loss, nitrate forms of fertiliser should not be used. Thus, matching the type of fertiliser with rainfall and moisture conditions in the soil could result in appreciable reductions in nitrogen loss (McTaggart et al. 1994). This is likely to be more beneficial and easier to manage than attempting to maintain a balance between appropriate water management and limiting denitrification or nitrate leaching. For example, trickle or drip irrigation systems which allow delivery of nitrogen to the area of maximum crop uptake enable the application rate to be matched to the plants' requirements. With careful operation, trickle systems can reduce deep percolation, runoff, and denitrification (Doerge et al. 1991). The aim of better water management should be to reduce denitrification by ensuring that the water-filled pore space of the soil does not exceed 60% (Smith et al. 1997; Mosier et al. 2002).

Returning crop residues to the soil instead of burning them allows reuse of the nitrogen contained in the residues. Incorporated residues can also improve soil structure, and reduce ammonia volatilisation by influencing the conditions of the underlying soil, and by acting as a medium through which ammonia must pass before being lost to the atmosphere (Aulakh et al. 1991; Freney et al. 1992b). Incorporating residues with high C/N ratio into soils will immobilise mineral nitrogen which can become available later when mineralised (Aulakh et al. 1991).

Optimising plant growth and uptake of nitrogen through management of the plant's total nutrient requirements is another means of increasing nitrogen use efficiency. The supply of one nutrient affects the absorption, distribution, or function of another nutrient, so that insufficient amounts of plant-available phosphorus, sulfur, potassium, or other nutrient will reduce nitrogen use efficiency. For example, nitrogen recovery in phosphorus-deficient corn was <40%, whereas it was 75% when adequate phosphorus was supplied (Oberle and Keeney 1990).

Site-specific nitrogen management is used to synchronise the supply and demand of nitrogen, and it can be used to manage nitrogen in labour-intensive, small-scale farming or highly mechanised, large-scale production fields (Dobermann and Cassman 2004). Optimum nitrogen rates vary spatially and seasonally; thus, diagnostic tools are required to assess soil or crop nitrogen status during the growing season to make decisions on the amount of nitrogen to be applied (Schroeder et al. 2000). One diagnostic measure is leaf greenness, and several techniques exist to measure this, including near-infrared leaf nitrogen analysis, chlorophyll meters, leaf colour charts, crop canopy reflectance sensors, and remote sensing (Giller et al. 2004). Significant increases in nitrogen use efficiency have been achieved through reductions in nitrogen use.

Decision support systems (DSS), based on comprehensive and process-based agro-ecosystem models, for optimum nitrogen fertiliser management have also been used recently. The advantage of such systems is the ability to integrate biophysical variables/interacting processes and management practices and economical-environmental considerations. The best management practices can be identified by simulating the combination of different management practices, such as interaction of nitrogen application rates and time with irrigation rate and time, and trade-off between economical and environmental interests. The GIS-based DSS for fertiliser application and irrigation for North China Plain, derived from the Water and Nitrogen Management Model (WNMM), has significantly assisted the dissemination of the best management fertiliser nitrogen practices with substantial economical impact (Chen et al. 2006).

Enhanced efficiency fertilisers

While the techniques described above have the potential to increase the effectiveness of applied nitrogen, considerable N losses still occur. For example, in flooded rice the time of application had a big effect on the agronomic efficiency of fertiliser nitrogen and ammonia volatilisation, but even with the best system devised, around 40% of the applied nitrogen was still lost by ammonia volatilisation, denitrification, or leaching (Bacon and Heenan 1987; Humphreys et al. 1988). In order to further reduce loss by these processes, alternative fertilisation techniques, such as the use of controlled release fertilisers, urease inhibitors, and nitrification inhibitors, need to be considered. These can be collectively referred to as enhanced efficiency fertilisers.

There have been numerous studies on enhanced efficiency fertilisers, either used alone or in combination in agroecosystems, with highly variable efficiencies demonstrated (Smith et al. 1997; Trenkel 1997; Zerulla et al. 2001; Drost et al. 2002; Singh et al. 2004; Watson 2005). The high variability in effectiveness is often due to a lack of understanding of the interaction of these chemicals with soil and environmental variables (Mosier et al. 2002). For example, the nitrification inhibitor dicyandiamide (DCD) was shown to be a very effective nitrification inhibitor under cold climatic conditions, but is less effective in warm/hot and wet climates due to its rapid decomposition (Zerulla et al. 2001; Singh et al. 2004; Di and Cameron 2004b; Hatch et al. 2005). Most field studies have concentrated on the effect on production (grain yield or biomass) and few have considered gaseous nitrogen loss and nitrate leaching. While many studies have been carried out in other countries, few have been conducted in Australia. Thus, there is a need to evaluate the effectiveness of various formulations and strategies under conditions applicable to Australia's major agroecological zones for fertiliser manufacturers and farmers.

Controlled release fertilisers

The supply of nitrogen by a single application of slow or controlled-release fertiliser should satisfy plant requirements and maintain low concentrations of mineral nitrogen in the soil throughout the growing season. As a result, labour and application costs should be low, nitrogen loss should be minimised, nitrogen use efficiency should increase, and yields should be improved.

Many different controlled release forms of nitrogen have been suggested (Peoples et al. 1995), and considerable advances have been made in the formulation of these materials. Shaviv (2005a, 2005b) has classified these fertilisers into 3 main types:

(i) inorganic low solubility compounds (e.g. magnesium ammonium phosphate);

(ii) organic low solubility compounds (e.g. urea formaldehyde and isobutylidenediurea);

(iii) coated materials in which a physical barrier controls the release (e.g. granules coated with hydrophobic polymers, or matrices in which the soluble fertiliser is dispersed so the dissolution of the fertiliser is restricted).

The coated fertilisers can be further divided into those coated with inorganic material (e.g. sulfur-coated urea), sulfur-coated fertiliser, which is further coated with an organic polymer (e.g. polymer-coated sulfur-coated urea), and those coated with organic polymers, viz. thermosetting resin-coated fertilisers and thermoplastic polymer-coated fertilisers.

Sulfur-coated urea was developed in the 1960s by the National Fertilizer Development Center and used with mixed success in a variety of applications, e.g. flooded rice (Prasad and De Datta 1979) and wheat (Mason 1985). Sulfur coatings provide highly variable nitrogen release patterns depending upon coating damage that might occur, and as much as one-third can be released instantaneously Addition of a polymer coating to sulfur-coated urea significantly improved its performance. Polymer sulfur-coated urea has improved ryegrass and bluegrass quality in 2 Pacific north-west climates (Miltner et al. 2004) and reduced leaching loss to only 1.7% of the applied nitrogen after application to turf lawn in southern New England (Guillard and Kopp 2004).

The main thermosetting resin-coated fertilisers are the alkyd-type resins (e.g. Osmocote) and those with polyurethane-like coatings such as Polyon, and Multicote (Trenkel 1997; Shaviv 2005a). Nutrient release from these materials is controlled by the coating thickness (Trenkel 1997; Shaviv 2005a). According to Shoji and Gandeza (1992), the most accurate controlled release of nutrients is provided by the polyolefin thermoplastic-coated fertilisers (e.g. Meister) developed by Chisso-Asahi Fertilizer Co., Japan. Fertiliser release is controlled by coating fertiliser particles with polyolefins, such as polyethylene and polypropylene, which have low water permeability, and ethylene vinyl acetate, which has high water permeability.

The pattern of nutrient release from coated fertilisers can be parabolic, linear, or sigmoidal and long- or short-term (Shaviv 2005a). Nitrogen uptake of seasonal crops and perennial species is generally sigmoidal (Shoji and Kanno 1994; Shoji et al. 2001; Shaviv 2005a). Because of the variety of polyolefin-coated fertilisers available it is now possible to use computers to program fertiliser release patterns to match the specific requirements of a crop, and Shoji (2005) illustrates how this can be used to supply nitrogen at the times of peak demand for flooded rice.

Use of polyolefin-coated urea instead of uncoated fertiliser has resulted in increased yields and nitrogen use efficiency in a range of crops including potatoes, rice, and direct-seeded onions (Mikkelsen et al. 1994; Shoji and Kanno 1994; Shoji et al. 2001; Drost et al. 2002; Fashola et al. 2002; Shoji 2005; Wu et al. 2005). Large reductions in the emission of nitrous oxide have also been achieved using polyolefin-coated ammonium nitrate (Minami 1994), polyolefin-coated ammonium sulfate (Nutricote; Smith et al. 1997), and polyolefin-coated urea (Shoji et al. 2001) instead of uncoated nitrogen fertiliser. However, no yield effect was found in irrigated cotton in Australia by using polyolefin-coated urea, although there were significant impacts on N uptake and mineral N (urea, ammonium, and nitrate) dynamics (Chen et al. 2008). Ammonium-based fertilisers have been coated with polyolefins for use in vegetable growing to prevent the build-up of nitrate, which affects quality and may constitute a health risk (Matsumoto 1991; Takebe et al. 1996; Shoji 2005; Wang et al. 2005). A further decrease in nitrate uptake by vegetables was achieved by adding the nitrification inhibitor DCD to the fertiliser before coating the mixture with polyolefin (Mimaki 2003).

However, it has been pointed out that use of controlled release fertilisers may result in nitrogen, in excess of the crop's requirements, remaining in the soil after harvest. This nitrogen may then be lost to the environment in the same manner as uncoated fertiliser (Delgado and Mosier 1996).

The use of controlled-release fertilisers in agriculture is still limited in spite of the technological developments and availability. Only about 10% of the total production is consumed in agriculture, and the remainder is used for lawns, golf courses, fruit trees, and vegetables (Shaviv 2005a). The main reason for the limited use seems to be the high cost, which may be 3-10 times the cost of conventional fertiliser (Shaviv 2000).

Urease inhibitors

Urea has become the most widely used form of fertiliser nitrogen, because it is the least expensive form of fertiliser available, and its high nitrogen content (46%) means lower transportation costs. Globally in developed countries urea consumption has stabilised at around 30 Mt, while in developing countries consumption is still increasing dramatically and was around 55 Mt in 2002 (IFA 2006). However, it has the disadvantage that considerable losses of nitrogen can occur if the urea is not incorporated into soil soon after application. Losses have ranged from negligible amounts to >50% of the nitrogen applied, depending upon fertiliser practice and environmental conditions (Peoples et al. 1995; Cai et al. 2002). The loss occurs by ammonia volatilisation after the urea is converted to ammonia at the soil surface by reaction with the enzyme urease. One approach to decreasing ammonia volatilisation is to find compounds that inhibit urease activity, thus allowing the urea to move into the soil before hydrolysis. The ammonia then released would be retained by the soil.

A large number of compounds with differing characteristics have been tested for their ability to inhibit urease activity (Medina and Radel 1988; Watson 2000, 2005; Kiss and Simihaian 2002). Some inhibit the enzyme by reacting with active sites on the enzyme or a key functional group elsewhere in the molecule, or by changing the conformation of the active site. Many organic and inorganic compounds and metal ions inhibit urease by reacting with the sulthydryl groups in the enzyme (e.g. mercapto compounds), others by complexing with nickel in the active site (e.g. hydroxamates), some by reacting with the carboxylic acid group (e.g. arylorganoboron compounds), and others because they are structural analogues of urea (e.g. thiourea, methyl urea, and phosphoryl di- and triamides) (Medina and Radel 1988).

The most effective compounds for the inhibition of urease activity appear to be the phosphoryl amides (e.g. N-(n-butyl) phosphoric triamide and cyclohexylphosphoric triamide (Chai and Bremner 1987; Keerthisinghe and Blakely 1995; Byrnes and Freney 1995), although hydroquinone and 2, 5-dimethyl p-benzoquinone can provide inhibition at high concentrations (Tomlinson 1970; Xu et al. 2005).

A host of natural products have been tested for their ability to inhibit urease activity, including coal and peat; humic substances; lignins and tannins; plant residues and extracts containing polyphenols and saponins; neem cake, oil, and extracts; karanja cake and mahua cake; and microbial products (Kiss and Simihaian 2002). In India the press cake from the production of neem (Azadirachta indica) oil has been shown to inhibit urease activity (Trenkel 1997), and when it was used to coat urea it reduced loss of nitrogen and improved nitrogen use efficiency (John et al. 1989). Patra et al. (2006) showed that the natural essential oil, dementholised oil, and terpenes of peppermint (Mentha spicata) significantly retarded soil urease activity. Natural inhibitors of urease activity have also been found in Artemisia annua (Patra et al. 2002), Ranunculus repens (Khan et al. 2006), and Aspergillus ochraccus (Linet al. 1997).

The compound which has been most widely tested for its capacity to reduce ammonia loss from urea is N-(n-butyl) thiophosphoric triamide (Trenkel 1997; Singh et al. 2004; Watson 2005). However, like the other thiophosphoryl triamides it is not a urease inhibitor. The thio compounds are the precursors of oxygen analogues which are the actual inhibitors. Numerous tests of the pure thio compounds in vitro have shown their total ineffectiveness. The thio compounds have to be converted to the oxygen analogues on contact with soil or other material before inhibition can occur (McCarty et al. 1989; Creason et al. 1990). It might seem to be more logical to market the oxygen analogue of N-(n-butyl) thiophosphoric triamide (viz. N-(n-butyl) phosphoric triamide), but the oxygen analogue is not sufficiently stable for it to be packaged and distributed for commercial application (Incitec Pivot, pers. comm.). N-(n-butyl) thiophosphoric triamide, on the other hand, seems to be quite stable (Hendrickson and Douglass 1993) although its effectiveness is controlled by temperature (Chai and Bremner 1987; Carmona et al. 1990). The results of Carmona et al. (1990) indicate that higher concentrations of N-(n-butyl) thiophosphoric triamide will be required to prevent ammonia loss from warm soils than for temperate soils.

Watson et al. (1994a, 1994b) found N-(n-butyl) thiophosphoric triamide very effective at low concentrations (0.01% of applied urea nitrogen) for reducing ammonia volatilisation (by ~50%) in field trials on temperate grassland. Its use also significantly delayed and reduced ammonia and nitrous oxide emissions from soil after application of urea, urine, and urea ammonium nitrate (Bronson et al. 1989b; Schlegel 1991; Grant et al. 1996; Wang and Douglas 1996; Singh et al. 2004) and produced significant improvements in nitrogen use efficiency of corn following application of urea ammonium nitrate (Fox and Piekielek 1993). In 21 upland field experiments, treating urea with N-(n-butyl) thiophosphoric triamide increased grain yields of maize by an average of 750 kg/ha (Bronson et al. 1989b). An additional 80 kg N/ha would need to be applied to obtain that increase in yield (Byrnes and Freney 1995). Similar positive results were reported by Hendrickson (1992) for maize fertilised with urea or urea ammonium nitrate in 78 trials conducted in the USA between 1984 and 1989.

Both N-(n-butyl) thiophosphoric triamide and cyclohexyl phosphoric triamide have been used successfully to control ammonia emission from animal wastes, to prevent environmental damage, and to produce a more balanced nitrogen/phosphorus fertiliser from manure (Varel 1997; Varel et al. 1999).

Nitrification inhibitors

Maintaining nitrogen in the ammonium form to soil would prevent its loss by both nitrification and denitrification. One method of doing this is to add a nitrification inhibitor with the fertiliser. This prevents or slows the microbial conversion of ammonium to nitrate and hence the leaching of nitrate and production of nitric oxide, and nitrous oxide by both nitrification and denitrification. While this technique does not always produce increased crop yields it does provide a tool for managing nitrate leaching and nitrous oxide production (Edmeades 2004).

Reliable data on the use of nitrification inhibitors in different crops and regions are not available. Surveys of USA farmers indicate that at present about 9% of the national maize area is treated with nitrification inhibitors, and this proportion has remained unchanged in recent years (Christensen 2002).

Many chemicals have been tested as nitrification inhibitors, but few are commercially available (Table 4) or have proven to be agronomically and economically effective (Slangen and Kerkhoff 1984; Prasad and Power 1995; McCarty 1999; Frye 2005). The persistence and behaviour of nitrification inhibitors in soil is determined by diffusion into the atmosphere, decomposition or degradation, differential movement in soils, sorption on clay or organic matter (Slangen and Kerkhoff 1984), and by environmental and edaphic factors, such as temperature, moisture, and soil texture (Prasad and Power 1995). While progress is being made towards understanding the mode of action of many inhibitors of ammonia oxidation, little is known about the action of others such as the heterocyclic nitrogen compounds (McCarty 1999).

Of the inhibitors listed in Table 4, the most extensively studied products are nitrapyrin, DCD, and more recently 3,4-dimethylpyrazole phosphate (Goos and Johnson 1999; Dittert et al. 2001; Pasda et al. 2001; Weiske et al. 2001a, 2001b; Zerulla et al. 2001; Calderon et al. 2005; Chao et al. 2005; Islam et al. 2007a, 2007b).

Nitrapyrin is often ineffective because of sorption on soil colloids, hydrolysis, and loss by volatilisation (Hoeft 1984; Liu et al. 1984), but it has reduced nitrogen losses and resulted in increased plant nitrogen uptake (Fillery and De Datta 1986; Chen et al. 1998a, 1998b). When Wolt (2004) evaluated the performance of nitrapyrin across research trials conducted in diverse environments over many years in Midwestern USA, he found that, on average, nitrapyrin increased corn yield by 7% and soil retention of nitrogen by 28%. It also decreased nitrogen leaching by 16% and nitrous oxide emission by 51%.

Dicyandiamide inhibited nitrification when ammoniacal fertilisers were applied to field crops and vegetables (Frye et al. 1989; Frye 2005) with the result that nitrogen remained longer in the soil in the ammonium form (Irigoyen et al. 2003). Yield increases have been obtained when DCD was applied to pastures (Di and Cameron 2002; Smith et al. 2005) and various cropping systems, e.g. maize (Ball-Coelho and Roy 1999), wheat (Rao 1996; Sharma and Kumar 1998; Rao and Popham 1999), and maize-wheat (Sharma and Prasad 1996). However, application of DCD does not always lead to yield increases (Mason 1987; Dachler 1993; Frye 2005) and in some cases can have deleterious effects on plant growth (Macadam et al. 2003). Yield increases usually occurred at low fertiliser application rates (Frye 2005).

Leaching of nitrate can be significantly reduced by addition of DCD (Ball-Coelho and Roy 1999; Serna et al. 2000; Di and Cameron 2002, 2004a). Treatment of urine patches on a fine sandy loam in New Zealand with DCD reduced nitrate leaching losses from 85 to 20-22 kg N/ha. year (Di and Cameron 2002, 2004a). The beneficial effect of the DCD was increased beyond the saving of nitrogen because it also reduced leaching of the cations associated with nitrate, calcium by 38 56% and magnesium by 21-42% (Di and Cameron 2004a, 2004c)

Because DCD effectively retards nitrification, when it is added to soil along with ammonium based fertilisers, emissions of nitric oxide and nitrous oxide are substantially reduced compared with fertiliser alone (Majumdar et al. 2000; Shoji et al. 2001; Vallejo et al. 2001; Singh et al. 2004; Hatch et al. 2005; Merino et al. 2005;). For example, Skiba et al. (1993) showed that addition of DCD reduced nitric oxide emission by about 92% and nitrous oxide emission by 40%. Significant reductions have also been reported for DCD-treated pig slurry (Vallejo et al. 2005) and DCD-treated animal urine patches in grazed perennial ryegrass white clover pastures (Di and Cameron 2003). Di and Cameron (2003) showed that repeated applications of DCD offered no advantage over a single application of DCD immediately after urine deposition.

However, the effect of DCD on reducing the rate of nitrification in soil is variable and in some cases no effect on nitrate leaching was obtained (Davies and Williams 1995; Beckwith et al. 1998). The effectiveness of DCD in soil is controlled by temperature, texture, and moisture content (Prasad and Power 1995; Irigoyen et al. 2003). With increasing temperature the inhibiting effect of DCD is greatly decreased (Bronson et al. 1989a; Irigoyen et al. 2003; Di and Cameron 2004b). Bronson et al. (1989a) found that the half-life of DCD in a sandy loam was reduced from 52 to 14 days when the temperature was increased from 8 [degrees]C to 22 [degrees]C, and Di and Cameron (2004b) observed a greater reduction in a silt loam.

A relatively new nitrification inhibitor, 3, 4-dimethylpyrazole phosphate (DMPP), was developed by the German company BASF AG (BASF 1999; Zerulla et al. 2001). It is generally more effective and longer lasting than DCD in inhibiting nitrification, and inhibition was achieved with lower rates of application (0.5-1.5 kg DMPP/ha). DMPP has been found to reduce nitrate and nitrite levels in soil after application of ammonium-based fertilisers and cattle slurry, leading to significantly lower nitric oxide and nitrous oxide emissions, and nitrate leaching, and to improve crop yields (Dittert et al. 2001; Pasda et al. 2001; Zerulla et al. 2001; Chao et al. 2005; Menendez et al. 2006). Weiske et al. (2001b) showed that DMPP reduced emission of nitrous oxide by 49% (averaged over 3 years), which was considerably more than DCD (average reduction 26%). European field trials demonstrated that addition of DMPP increased yields of winter wheat, wetland rice, maize, potatoes, sugar beets, carrots, lettuce, radish, cauliflower, and onions, allowed lower rates of nitrogen fertiliser, or permitted fewer applications to be used to attain the same yields as treatments without DMPP (Pasda et al. 2001).

The effectiveness of DMPP, like DCD, is influenced by temperature, soil texture, and moisture (Barth et al. 2001; Pasda et al. 2001; Merino et al. 2005). Merino et al. (2005) found that DMPP applied with cattle slurry was able to maintain soil mineral nitrogen in the ammonium form for 22 days and reduce nitrous oxide emission by 69% in autumn, but in spring its effect on soil mineral N lasted for only 7-14 days, and reduced nitrous oxide loss by 48%.

Other nitrification inhibitors that have been used successfully in field trials include acetylene, substituted acetylenes, etridiazole, and a natural product from the Neem tree (Azadirachta melia). Acetylene is a potent inhibitor of nitrification, but because it is a gas, it is difficult to add and keep in soil at the correct concentration to inhibit the oxidation of ammonium. Calcium carbide coated with layers of wax and shellac has been used to provide a slow-release source of acetylene to inhibit nitrification (Mosier 1994). This technique has increased the yield or recovery of nitrogen in irrigated wheat, maize, cotton, and flooded rice (Bronson and Mosier 1991; Bronson et al. 1992; Freney et al. 1992a, 1993; Zhang et al. 1992). Another product, a polyethylene matrix containing small particles of calcium carbide and various additives to provide controlled water penetration and acetylene release, has been developed as an alternative slow-release source of acetylene. In laboratory studies, this matrix inhibited nitrification for 90 days and considerably slowed the oxidation for 180 days (Freney et al. 2000). It also retarded nitrification in an irrigated corn field for at least 48 days (Randall et al. 2002). The substituted acetylenes 2-ethynylpyridine and phenylacetylene are very effective inhibitors of nitrification in the field (Freney et al. 1993; Chen et al. 1994, 1998a, 1998b), but their current price restricts their use by farmers.

Etridiazole (Terrazole, Dwell) was found to be a very effective nitrification inhibitor in laboratory investigations (Liu et al. 1984; Rafii et al. 1984; McCarty and Bremner 1990), and it has been shown to inhibit nitrification for prolonged periods in the field (Somda et al. 1989; Rochester et al. 1994) and to substantially improve yields for a variety of field and horticultural crops (Somda et al. 1990) and irrigated cotton (Rochester et al. 1994, 1996).

Various products (cake and oil) from the seeds of the Neem tree have been tested to determine whether they could be used as cheap nitrification inhibitors for resource-poor Indian farmers (Majumdar et al. 2000; Malla et al. 2005). Field experiments on the Indo-Gangetic plain showed that application of neem cake and neem oil with the fertiliser significantly reduced the emission of nitrous oxide. Addition of neem cake also significantly increased the yield of rice (Malla et al. 2005).

Unless care is taken to place ammonium-based fertilisers below the soil surface, use of nitrification inhibitors may result in increased ammonia volatilisation (Rodgers 1983; Chaiwanakupt et al. 1996).

Potential for use of enhanced efficiency fertilisers in Australia

Research suggests that the effectiveness of different controlled release fertilisers, and urease and nitrification inhibitors will depend upon crop, soil climate, and management factors. The broadacre agricultural industries in Australia which have been identified as high nitrogen users are those producing cereals, sugarcane, cotton, and pasture (Table 1). Some dairy pastures receive up to 300 kg N/ha. year (Eckard 2004). Horticultural cropping and turf production are also big users of nitrogen, but these industries are beyond the scope of this review. Each of these industries is likely to benefit from the use of the enhanced fertilisation techniques, but the best technique for each crop is likely to vary.

The major wheat-producing regions are in southern Western Australia, New South Wales, South Australia, and western Victoria where the climate is temperate and the soils are mainly Chromosols, Sodosols, Vertosols, and Calcarasols (Isbell 1996). The pasture-producing areas that have high nitrogen inputs are the rainfed or irrigated dairying regions (Eckard 2004). Most of the dairy pastures are in Victoria, which is responsible for 64% of Australia's milk production (Dairy Australia 2006), and most of the dairy cattle are in the Western District (rainfed), Goulburn (irrigated), and Gippsland (ABS 2005). The main soils in these regions are, respectively, Chromosols, Sodosols, and Vertosols; Sodosols; and Dermosols and Ferrosols. The climate in these regions is temperate. Sugarcane is grown along a 2000-km strip of land on the east coast of Australia from northern New South Wales to north Queensland. About one-third of this crop is grown in north Queensland from Ingham to Mossman. This area has a humid tropical climate, and sugarcane is grown on soils formed from alluvial deposits, the deep red and yellow friable loams and the krasnozems (Wood 1991). In the subtropical areas, the crop is grown on red loams around Bundaberg, and on acid sulfate soils in the coastal lowland regions. Cotton is grown throughout NSW and Queensland on alkaline heavy clay soils where the climate ranges from temperate to subtropical.

Urease inhibitors are expected to be most beneficial on soils where loss of ammonia from application of urea fertiliser is high. This is likely to be when urea is applied to the surface of pasture soils (e.g. in the dairy industry) or other soils which have high urease activity due to lack of cultivation or the accumulation of organic matter (e.g. sugarcane trash). Ammonia loss will also occur when incorporation of urea is difficult and there is little opportunity for the urea to move into the soil with infiltrating water (e.g. rainfed wheat). Nitrification inhibitors are likely to have the greatest benefit on soils where nitrogen losses due to leaching or denitrification are large. Leaching losses are more likely to occur on coarse-textured, free-draining soils under heavy rainfall (e.g. sugarcane soils in the tropics) than on fine-textured clay soils with low rainfall (cotton soils in western NSW). Losses due to denitrification are expected to be large in warm, flooded, or waterlogged soils (cotton and rice soils), in soils to which plant residues have been added (sugarcane and banana soils), and in dung and urine patches (pasture soils). Benefits from the use of controlled release fertilisers could potentially occur in all the agricultural industries, as their use should limit losses by all processes.

The choice of controlled release fertiliser, urease inhibitor, or nitrification inhibitor is likely to be determined more by factors such as price and availability rather than by degree of effectiveness, as many of the compounds shown to be very effective in the laboratory and small-scale trials are not available commercially. Available products which have the potential to increase yield, nitrogen use efficiency, or loss of nitrogen are described below.

Controlled release fertilisers

The controlled release fertilisers that appear to show the greatest potential for dryland and irrigated cropping, and pasture are (i) a polymer-coated urea (Environmentally Smart Nitrogen; Agrium 2006); (ii) a polyolefin-coated urea (Meister; Chisso Corporation 2006); and (iii) a humic-acid-coated urea (Black Urea; Advanced Nutrients Australia 2006).

Environmentally Smart Nitrogen has been extensively used in the USA and Canada and recently in trials in subtropical Queensland. It maximised nitrogen use efficiency and minimised nitrogen losses to the environment (Blaylock et al. 2005; Agrium 2006). Meister comes in several forms having different release types and times. Meister-SS15 shows a sigmoidal-type release, with a lag period of 70 days and a release period of 80 days (Shoji et al. 2001). This makes it ideal for dryland wheat, which requires nitrogen fertilisation approximately 80 days after sowing to supply nitrogen for grain-fill. Urea coated with humic acid has significantly reduced nitrogen loss and enhanced nitrogen uptake by dryland wheat in field trials at Quirindi, NSW, and increased dryland pasture yields compared with urea (Advanced Nutrients Australia 2006). Addition of humic acid to urea has also reduced ammonia loss from acid soils (Garcia Serna et al. 1996; Siva et al. 2000).

Urease inhibitors

The most readily available compound, N-(n-butyl) thiophosphoric triamide, is sold in Australia as Agrotain, which contains 20-25% active ingredient (IMC-Agrico 1997). Agrotain is marketed by Incitec Pivot Ltd in the following formulations: (i) Green Urea 14, which contains 45.8% nitrogen as urea and Agrotain @ 5.0 L/t to reduce the loss of ammonia by volatilisation for up to 14 days; and (ii) Green Urea 7, which contains 45.9% nitrogen and Agrotain @ 3.0 L/t to reduce ammonia volatilisation for up to 7 days (Incitec Pivot Ltd 2006).

Nitrification inhibitors

The products which show the greatest potential for reducing nitrogen loss from agricultural industries in Australia are (i) DMPP (rainfed wheat and pasture), (ii) DCD (rainfed and irrigated pasture, wheat), and (iii) etridiazole (irrigated cotton). DMPP seems to be the best product because of its positive effects on yield and nitrogen loss at low concentrations, and because of its stability and lack of movement in soil. It may need to be applied at slightly higher concentrations in warm conditions. It is marketed as ENTEC by BASF and is distributed by Incitec-Pivot in Australia (Incitec Pivot Ltd 2006). DCD (marketed as Didin by SKW Trotsberg, Germany) needs to be applied at higher rates than DMPP. It is unstable at high temperatures, and thus is likely to be more effective when used during winter and autumn.

Further testing of these materials under a range of conditions is required to select the best material for a particular industry in Australia, and to determine the economics of its use.

Manuscript received 27 November 2007, accepted 19 March 2008

References

ABS (Australian Bureau of Statistics) (2005) 'Agricultural State Profile, Victoria, 2003-04 (7123.2.55.001).' (Australian Bureau of Statistics: Canberra)

Advanced Nutrients Australia (2006) www.advancednutrients.com/.

AGO (Australian Greenhouse Office) (2007) 'National Greenhouse Gas Inventory 2005.' (Australian Greenhouse Office: Canberra) Agrium (2006) www.agrium.com

Aulakh MS, Doran JW, Walters DT, Mosier AR, Francis DD (1991) Crop residue type and placement effects on denitrification and mineralisation. Soil Science Society of America Journal 55, 1020-1025.

Bacon PE, Freney JR (1989) Nitrogen loss from different tillage systems and the effect on cereal grain yield. Fertilizer Research 20, 59-66. doi: 10.1007/BF01055429

Bacon PE, Heenan DP (1987) Nitrogen budgets for intensive rice growing in southern Australia. In 'Efficiency of nitrogen fertilizers for rice'. (Eds JR Freney, R Wetselaar, ACF Trevitt, JR Simpson) pp. 89-95. (Interntional Rice Research Institute: Los Banos, Philippines)

Ball-Coelho BR, Roy RC (1999) Enhanced ammonium sources to reduce nitrate leaching. Nutrient Cycling in Agroecosytems 54, 73-80. doi: 10.1023/A:1009773428011

Barth G, von Tucher S, Schmidhalter U (2001) Influence of soil parameters on the effect of 3,4-dimethylpyrazole-phosphate as a nitrification inhibitor. Biology and Fertility of Soils 34, 98-102. doi: 10.1007/ s003740100382

BASF (1999) 'Dungen mit einer neuen Technologie: Innovationin der Dungnng. ENTEC.' (Agrarzentrum Limburgerhof: Limburgerhof, Germany)

Beckwith CP, Cooper J, Smith KA, Shepherd MA (1998) Nitrate leaching loss following applications of organic manure to sandy soils in arable cropping. I. Effects of application time, manure type, overwinter crop cover and nitrification inhibition. Soil Use and Management 14, 123-130. doi: 10.1111/j.1475-2743.1998.tb00629.x

Blaylock AD, Binford GD, Dowbenko RD, Kaufmann J, Islam R (2005) ESN, controlled release nitrogen for enhanced nitrogen efficiency and improved environmental safety. In 'Proceedings of the 3rd International Nitrogen Conference'. (Eds ZL Zhu, K Minami, GX Xing) pp. 381-390. (Science Press: Beijing)

Bronson KF, Mosier AR (1991) Effect of encapsulated calcium carbide on dinitrogen, nitrous oxide, methane, and carbon dioxide from flooded rice. Biology and Fertility of Soils 11, 116-120. doi: 10.1007/BF00336375

Bronson KF, Mosier AR, Bishnoi SR (1992) Nitrous oxide emissions in irrigated corn as affected by nitrification inhibitors. Soil Science Society of America Journal 56, 161-165.

Bronson KF, Touchton JT, Hauck RD (1989a) Decomposition rate of dicyandiamide and nitrification inhibition. Communications in Soil Science and Plant Analysis 20, 2067-2078.

Bronson KF, Touchton JT, Hiltbold AE, Hendrickson LL (1989b) Control of ammonia volatilization with N-(n-butyl) thiophosphoric triamide in loamy sands. Communications in Soil Science and Plant Analysis 20, 1439-1451.

Byrnes BH, Freney JR (1995) Recent developments on the use of urease inhibitors in the tropics. Fertilizer Research 42,251-259. doi: 10.1007/ BF00750519

Cai G, Chen D, White RE, Fan XH, Pacholski A, Zhu ZL, Ding H (2002) Gaseous nitrogen losses from urea applied to maize on a calcareous fluvo-aquic soil in the North China Plain. Australian Journal of Soil Research 40, 737-748. doi: 10.1071/SR01011

Calderon FJ, McCarty GW, Reeves JB (2005) Nitrapyrin delays denitrification on manured soils. Soil Science 170, 350-359. doi: 10. 1097/01.ss.0000169905.94861.c7

Cameron KC, Di HJ, Condron LM (2002) Nutrient and pesticide transfer from agricultural soils to water in New Zealand. In 'Agriculture, hydrology and water quality'. (Eds P Haygarth, S Jarvis) pp. 373-393. (CABI: Wallingford, UK)

Carmona G, Christianson CB, Byrnes BH (1990) Temperature and low concentration effects of the urease inhibitor N-(n-butyl) thiophosphoric triamide (nBTPT) on ammonia volatilisation from urea. Soil Biology & Biochemistry 22, 933-937. doi: 10.1016/ 0038-0717(90)90132-J

Chai HS, Bremner JM (1987) Evaluation of some phosphoroamides as soil urease inhibitors. Biology and Fertility of Soils 3, 189-194. doi: 10.1007/ BF00640628

Chaiwanakupt P, Freney JR, Keerthisinghe DG, Phongpan S, Blakeley RL (1996) Use of urease, algal and nitrification inhibitors to reduce nitrogen loss and increase grain yield of flooded rice (Oryza sativa L.). Biology and Fertility of Soils 22, 89-95. doi: 10.1007/BF00384438

Chao X, Wu LH, Ju XT, Zhang FS (2005) Role of nitrification inhibitor DMPP (3,4-dimethylpyrazole phosphate) in N[O.sub.3] -N accumulation in greengrocery (Brassica campestris L. ssp chinensis) and vegetable soil. Journal of Environmental Sciences (China) 17, 81-83.

Chapman LS, Haysom MB, Saffigna PG, Freney JR (1991) The effect of placement and irrigation on the efficiency of use of (sup.15]N labelled urea by sugarcane. Proceedings of the Australian Society of Sugar Cane Technologists 13, 44-52.

Chen DL, Freney JR, Mosier AR, Chalk PM (1994) Reducing denitrification loss with nitrification inhibitors following presowing applications of fertiliser nitrogen to cotton fields. Australian Journal of Experimental Agriculture 34, 75-83. doi: 10. 1071/EA9940075

Chen DL, Chalk PM, Freney JR, Luo QX (1998a) Nitrogen transformations in a flooded soil in the presence and absence of rice plants: 1. Nitrification. Nutrient Cycling in Agroecosystems 51, 259-267. doi: 10. 1023/A: 1009736729518

Chen DL, Chalk PM, Freney JR (1998b) Nitrogen transformations in a flooded soil in the presence and absence of rice plants. 2. Denitrification. Nutrient Cycling in Agroecosystems 51, 26-279. doi: 10.1023/ A: 1009726524817

Chen D, White RE, Li Y, Zhang JB, Li BG, et al. (2006) Conservation management of water and nitrogen in the North China Plain. In 'Agricultural water management in China'. (Eds IR Willett, ZY Gao) pp. 26-38. (ACIAR: Canberra)

Chen D, Freney JR, Rochester IJ, Constable GA, Mosier AR, Chalk PM (2008) Evaluation of an olefine coated urea as a fertiliser for irrigated cotton. Nutrient Cycling in Agroecosystems (In press).

Chisso Corporation (2006) Meister. www.chisso.co.jp/english/index.asp

Christensen LA (2002) 'Soil, nutrient, and water management systems used in U.S. corn production'. Agriculture Information Bulletin No. 774. (Economic Research Service, United States Department of Agriculture: Washington, DC)

Creason GL, Schmitt MR, Douglass EA, Hendrickson LL (1990) Urease inhibitory activity associated with N-(n-butyl) thiopbosphoric triamide is due to the formation of its oxon analogue. Soil Biology & Biochemistry 22, 209-211. doi: 10.1016/0038-0717 (90)90088-H

Dachler M (1993) The effect of dicyandiamide-containing nitrogen fertilizers on root crops. 2. The effect on grain-maize and potatoes. Bodenkultur 44, 119-125.

Dairy Australia (2006) Australian Dairy Industry in Focus 2006. Dairy Australia.

Davies DM, Williams PJ (1995) The effect of the nitrification inhibitor dicyandiamide on nitrate leaching and ammonia volatilization: AUK nitrate sensitive areas perspective. Journal of Environmental Management 45, 263-272. doi: 10.1006/jema.1995.0074

De Datta SK, Trevitt ACF, Freney JR, Obcemea WN, Real JG, Simpson JR (1989) Measuring nitrogen losses from lowland rice using bulk aerodynamic and nitrogen-15 balance methods. Soil Science Society of America Journal 53, 1275-1281.

Delgado JA, Mosier AR (1996) Mitigation alternatives to decrease nitrous oxide emissions and urea-nitrogen loss and their effect on methane flux. Journal of Environmental Quality 25, 1105-1111.

Di HJ, Cameron KC (2002) The use of a nitrification inhibitor, dicyandiamide (DCD), to decrease nitrate leaching and nitrous oxide emissions in a simulated grazed and irrigated grassland. Soil Use and Management 18, 395-403. doi: 10. 1079/SUM2002151

Di HJ, Cameron KC (2003) Mitigation of nitrous oxide emissions in sprayirrigated grazed grassland by treating the soil with dicyandiamide, a nitrification inhibitor. Soil Use and Management 19, 284-290.

Di HJ, Cameron KC (2004a) Treating grazed pasture soil with a nitrification inhibitor, eco-nTM, to decrease nitrate leaching in a deep sandy soil under spray irrigation. New Zealand Journal of Agricultural Research 47, 351-361.

Di HJ, Cameron KC (2004b) Effects of temperature and application rate of a nitrification inhibitor, dicyandiamide (DCD), on nitrification rate and microbial biomass in a grazed pasture soil. Australian Journal of Soil Research 42, 927-932. doi: 10.1071/SR04050

Di HJ, Cameron KC (2004c) Effects of the nitrification inhibitor dicyandiamide on potassium, magnesium and calcium leaching in grazed grassland. Soil Use and Management 20, 2-7. doi: 10.1079/ SUM2003205

Dittert K, Bol R, King R, Chadwick D, Hatch D (2001) Use of a novel nitrification inhibitor to reduce nitrous oxide emission from [sup.15]N-labelled dairy slurry injected into soil. Rapid Communications in Mass Spectrometry, 15, 1291 1296. doi: 10.1002/rcm.335

Dobermann A, Cassman KG (2004) Environmental dimensions of fertilizer nitrogen: What can be done to increase nitrogen use efficiency and ensure global food security? In 'Agriculture and the nitrogen cycle: assessing the impacts of fertilizer use on food production and the environment'. (Eds AR Mosier, JK Syers, JR Freney) pp. 261-278. (Island Press: Washington, DC)

Doerge TA, Roth RL, Gardner BR (1991) 'Nitrogen fertilizer management in Arizona.' (College of Agriculture, University of Arizona: Tucson, AR)

Drost R, Koenig R, Tindall T (2002) Nitrogen use efficiency and onion yield increased with a polymer-coated nitrogen source. HortScienee 37, 338-342.

Eckard RJ (2004) Filling feed gaps with strategic fertiliser use. In 'Proceedings of the 45th Annual Conference of the Grassland Society of Southern Australia'. pp. 5-10. (Grassland Society of Southern Australia: Warragul, Vic.)

Eckard R J, Chen D, White RE, Chapman DF (2003) Gaseous nitrogen loss from temperate perennial grass and clover dairy pastures in south-eastern Australia. Australian Journal of Agricultural Research 54, 561-570. doi: 10.1071/AR02100

Edmeades DC (2004) Nitrification and urease inhibitors. A review of the national and international literature on their effects on nitrate leaching, greenhouse gas emissions and ammonia volatilisation from temperate legume based pastoral systems. Environment Waikato Technical Report 2004/22.

FAO (Food and Agriculture Organization) (2007) 'FAOSTAT database collections.' www.apps.fao.org. (FAO: Rome)

FAO, IFA, IFDC, IPI, PPI (Food and Agriculture Organization of the United Nations, International Fertilizer Industry Association, International Fertilizer Development Center, International Potash Institute, Phosphate and Potash Institute) (2002) 'Fertilizer use by crop'. 5th edn (FAO: Rome)

Fashola OO, Hayashi K, Wakatsuki T (2002) Effect of water management and polyolefin-coated urea on growth and nitrogen uptake of indica rice. Journal of Plant Nutrition 25, 2173-2190. doi: 10.1081/ PLN-120014069

Fillery IRP, De Datta SK (1986) Ammonia volatilization from nitrogensources applied to rice fields. I. Methodology, ammonia fluxes, and N- 15 loss. Soil Science Society of America Journal 50, 80-86.

Fox RH, Piekielek WP (1993) Management and urease inhibitor effect on nitrogen use efficiency in no-till corn. Journal of Production Agriculture 6, 195-200.

Freney JR, Smith CJ, Mosier AR (1992a) Effect of a new nitrification inhibitor (wax coated calcium carbide) on transformations and recovery of fertilizer nitrogen by irrigated wheat. Fertilizer Research 32, 1-11. doi: 10.1007/BF01054388

Freney JR, Denmead OT, Wood AW, Saffigna PG, Chapman LS, Ham GJ, Humey AP, Stewart RL (1992b) Factors controlling ammonia loss from trash covered sugarcane fields fertilized with urea. Fertilizer Research 31,341-349. doi: 10.1007/BF01051285

Freney JR, Chen DL, Mosier AR, Rochester IJ, Constable GA, Chalk PM (1993) Use of nitrification inhibitors to increase fertilizer nitrogen recovery and lint yield in irrigated cotton. Fertilizer Research 34, 37-44. doi: 10. 1007/BF00749958

Freney JR, Randall PJ, Smith JWB, Hodgkin J, Harrington KJ, Morton TC (2000) Slow release sources of acetylene to inhibit nitrification in soil. Nutrient Cycling in Agroecosystems 56, 241-251. doi: 10.1023/ A:1009866902673

Frye W (2005) Nitrification inhibition for nitrogen efficiency and environment protection. In 'Proceedings of the IFA International Workshop on Enhanced-Efficiency Fertilizers'. Frankfurt, Germany, 28-30 June 2005.

Frye WW, Graetz DA, Locasio SJ, Reeves DW, Touchton JT (1989) Dicyandiamide as a nitrification inhibitor in crop production in the Southeastern USA. Communications in Soil Science and Plant Analvsis 20, 1969 1999.

Garcia Serna J, Juarez M, Jorda J, Sanchez Andreu J (1996) Influence of organic compounds on nitrogen-fertilizer solubilization. Communications in Soil Science and Plant Analysis 27, 2485-2491.

Giller KE, Chalk P, Dobermann A, Hammond L, Heffer P, Ladha JK, Nyamudeza P, Maene L, Ssali H, Freney J (2004) Emerging technologies to increase the efficiency of use of fertilizer nitrogen. In 'Agriculture and the nitrogen cycle: assessing the impacts of fertilizer use on food production and the environment'. (Eds AR Mosier, JK Syers, JR Freney) pp. 35-51. (Island Press: Washington, DC)

Goos RJ, Johnson BE (1999) Performance of two nitrification inhibitors over a winter with exceptionally heavy snowfall. Agronomy Journal 91, 1046-1049.

Granli T, Bockman OC (1994) Nitrous oxide from agriculture. Norwegian Journal of Agricultural Science 128(Supplement No. 12).

Grant CA, Jia S, Brown KR, Bailey LD (1996) Volatile losses of N[H.sub.3] from surface applied urea and urea ammonium nitrate with and without the urease inhibitors NBTP or ammonium thiosulphate. Canadian Journal of Soil Science 76, 417-119.

Guillard K, Kopp KL (2004) Nitrogen fertilizer form and associated nitrate leaching from cool-season lawn turf. Journal of Environmental Quality 33, 1822-1827.

Hatch D, Trindade H, Cardenas L, Cameiro J, Hawkins J, Scholefield D, Chadwick D (2005) Laboratory study of the effects of two nitrification inhibitors on greenhouse gas emissions from a slurry-treated arable soil: impact of diurnal temperature cycle. Biology and Fertility of Soils 41, 225-232. doi: 10.1007/s00374-005-0836-9

Hendrickson LL (1992) Corn yield response to the urease inhibitor NBPT 5-year summary. Journal of Production Agriculture 5, 131-137.

Hendrickson LL, Douglass EA (1993) Metabolism of the urease inhibitor N-(n-butyl) thiophosphoric triamide (NBPT) in soils. Soil Biology & Biochemistry 25, 1613-1618. doi: 10.1016/ 0038-0717(93)90017-6

Hoeft RG (1984) Current status of nitrification inhibitor use in U.S. agriculture. In 'Nitrogen in Crop Production'. (Ed. RD Hauck) pp. 561-570. (American Society of Agronomy: Madison, WI)

Hooper P (2004) Strategic post sowing applications of nitrogen. Grains Research and Development Corporation Research Update for Growers, Balaklava, SA Southern Region, August 2004.

Humphreys E, Freney JR, Muirhead WA, Denmead OT, Simpson JR, Leuning R, Trevitr ACF, Obcemea WN, Wetselaar R, Cai GX (1988) Loss of ammonia after application of urea at different times to dry-seeded, irrigated rice. Fertilizer Research 16, 47-57. doi: 10.1007/ BF01053314

Humphreys E, Freney JR, Constable GA, Smith JWB, Lilley D, Rochester IJ (1990) The fate of your N fertilizer. In 'Proceedings of the 5th Australian Cotton Conference'. pp. 161-164.

IFA (International Fertilizer Industry Association) (2006) Annual Report 2005. International Fertilizer Industry Association, Paris.

IMC-Agrico (International Minerals & Chemicals Co--Agrico) (1997) 'Urease inhibitor Agrotain.' Product Information Guidebook. pp. 1-43. (IMC-Agrico)

Incitec Pivot Ltd (2006) www.pivot.com.au/

IPCC (Intergovernmental Panel on Climate Change) (1997) 'Revised 1996 IPCC guidelines for national greenhouse gas inventories.' (The Organization for Economic Cooperation & Development: Paris)

Irigoyen I, Muro J, Azpilikueta M, Aparicio-Tejo P, Lamsfus C (2003) Ammonium oxidation kinetics in the presence of nitrification inhibitors DCD and DMPP at various temperatures. Australian Journal of Soil Research 41, 1177-1183. doi: 10.1071/SR02144

Isbell RF (1996) 'The Australian Soil Classification.' Australian Soil and Land Survey Handbook. (CSIRO: Melbourne)

Islam A, Chen D, White RE (2007a) Heterotrophic and autotrophic nitrification in two acid pasture soils. Soil Biology & Biochemistry 39, 972-975. doi: 10.1016/j.soilbio.2006.11.003

Islam A, Chen D, White RE (2007b) Developing a technique to quantify heterotrophic and autotrophic nitrification in acid pasture soils. Communications in Soil Science and Plant Analysis 38, 2309-2321.

John PS, Buresh RJ, Pandey RK, Prasad R, Chua TT (1989) Nitrogen-15 balances for urea and neem-coated urea applied to lowland rice following two cowpea cropping systems. Plant and Soil 120, 233-241. doi: 10.1007/BF02377073

Johnkutty I, Palaniappan SP (1996) Use of a chlorophyll meter for nitrogen management in lowland rice. Fertilizer Research 45, 21-24. doi: 10.1007/BF00749877

Keerthisingbe DG, Blakely RL (1995) Inhibition of Jack bean urease by phosphorictriamides and thiophosphorictriamides. Soil Biology & Biochemistry. 27, 739-742. doi: 10.1016/0038-0717(95)00002-V

Keerthisingbe DG, Freney JR, Mosier AR (1993) Effect of wax-coated calcium carbide and nitrapyrin on nitrogen loss and methane emission from dry-seeded flooded flee. Biology and Fertility of Soils 16, 71-75. doi: 10.1007/BF00336519

Khan WN, Lodhi MA, Ali I, Azhar-Ul-Haq, Malik A, Bilal S, Gul R, Choudhary MI (2006) New natural urease inhibitors from Ranunculus repens. Journal of Enzyme Inhibition and Medicinal Chemistry 21, 17-19. doi: 10.1080/14756360500319210

Kiss S, Simihaian M (2002) 'Improving efficiency of urea fertilizers by inhibition of soil urease activity.' (Kluwer Academic Publishers: Dordrecht, The Netherlands)

Lin XJ, Chen JC, Zhen SL, Liu ZZ, Freney JR (1997) Studies on characteristics, crystal structure and effectiveness of urease inhibitor from Aspergillus ochraccus wilh. Jiegou Huaxue 16, 473-474.

Liu SL, Varsa EC, Kapusta G, Mburu DN (1984) Effect of Etridiazole and Nitrapyrin treated N fertilizers on soil mineral N status and wheat yields. Agronomy Journal 76, 265-270.

Macadam XMB, del Prado A, Merino P, Estavillo JM, Pinto M, Gonzales-Murua C (2003) Dicyandiamide and 3,4-dimethyl pyrazole phosphate decrease [N.sub.2]O emissions from grassland but dicyandiamide produces deleterious effects on clover. Journal of Plant Physiology 160, 1517-1523. doi: 10.1078/0176-1617-01006

Majumdar D, Kumar S, Pathak H, Jain MC, Kumar U (2000) Reducing nitrous oxide emissions from an irrigated rice field of North India with nitrification inhibitors. Agriculture, Ecosystems & Environment 81, 163-169. doi: 10.1016/S0167-8809(00)00156-0

Malla G, Bhatia A, Pathak H, Prasad S, Jain N, Singh J (2005) Mitigating nitrous oxide and methane emissions from soil in rice-wheat systems in Indo-Gangetic plain with nitrification and urease inhibitors. Chemosphere 58, 141-147. doi: 10.1016/j.cbemosphere.2004.09.003

Mason MG (1985) Sulfur-coated urea as a source of nitrogen for cereals in Western Australia. Australian Journal of Experimental Agriculture 25, 913-921. doi: 10.1071/EA9850913

Mason MG (1987) Effects of dicyandiamide (a nitrification inhibitor) on leaching of nitrogen and growth of cereals. Australian Journal of Experimental Agriculture 27, 127-133. doi: 10.1071/EA9870127

Matsumoto M (1991) Studies on the occurrence of Gomo-sho of Chinese cabbage and its prevention. Bulletin of the Toyama Agricultural Research Center 11, 1-92.

McCarty GW (1999) Modes of action of nitrification inhibitors. Biology and Fertility of Soils 29, 1-9. doi: 10.1007/s003740050518

McCarty GW, Bremner JM (1990) Persistence of effects of nitrification inhibitors added to soils. Communications in Soil Science and Plant Analysis 21,639-648.

McCarty GW, Bremner JM, Chai HS (1989) Effect of N-(n-butyl) thiophosphoric triamide on hydrolysis of urea by plant, microbial and soil urease. Biology and Fertility of Soils 8, 123-127.

McLenaghen RD, Cameron KC, Lampkin NH, Daly ML, Deo B (1996) Nitrate leaching from ploughed pasture and the effectiveness of winter catch crops in reducing leaching losses. New Zealand Journal of Agricultural Research 39, 413-420.

McTaggart IP, Clayton H, Smith KA (1994) Nitrous oxide flux from fertilized grassland: strategies for reducing emissions. In 'Non-C[O.sub.2] greenhouse gases: why and how to control?'. (Eds J Van Ham, LJ Janssen, RJ Swart) pp. 421-426. (Kluwer Academic Publishers: Dordrecht, The Netherlands)

Medina R, Radel RJ (1988) Mechanisms of urease inhibition. In 'Ammonia volatilization from urea fertilizers'. Bulletin Y-206. (Eds BR Book, DE Kissel) pp. 137-174. (National Fertilizer Development Center: Muscle Shoals, AL)

Menendez S, Merino P, Pinto M, Gonzalez-Murua C, Estavillo JM (2006) 3,4-Dimethylpyrazol phosphate effect on nitrous oxide, nitric oxide, ammonia, and carbon dioxide emissions from grasslands. Journal of Environmental Quality 35, 973-981. doi: 10.2134/jeq2005.0320

Merino P, Menendez S, Pinto M, Gonzalez-Murua C, Estavillo JM (2005) 3, 4-Dimethylpyrazole phosphate reduces nitrous oxide emissions from grassland after slurry application. Soil Use and Management 21, 53-57. doi: 10. 1079/SUM2005292

Mikkelsen RL, Williams HM, Behel AD Jr (1994) Nitrogen leaching and plant uptake from controlled-release fertilizers. Fertilizer Research 37, 43-50. doi: 10.1007/BF00750672

Milmer ED, Stahnke GK, Johnstone WJ, Golob CT (2004) Late fall and winter nitrogen fertilization of turfgrass in two pacific northwest climates. HortScience 39, 1745-1749.

Mimaki N (2003) Influences of Dd-Meister (dicyandiamide containing polyolefin coated urea) on the growth and contents of oxalic acid and nitrate of spinach. Agriculture and Science 4, 11-14.

Minami K (1994) Effect of nitrification inhibitors and slow-release fertilizer on emission of nitrous oxide from fertilized soils. In 'C[H.sub.4] and [N.sub.2]0; global emissions and controls from rice fields and other agricultural and industrial sources'. NIAES Series 2. (Eds K Minami, A Mosier, R Sass) pp. 187-196. (Yokendo Publishers: Tokyo)

Minami K (1997) Atmospheric methane and nitrous oxide: sources, sinks and strategies for reducing agricultural emissions. Nutrient Cycling in Agroecosystems 49, 203-211. doi: 10.1023/A:1009730618454

Mosier AR (1994) Nitrous oxide emission from agricultural soils. Fertilizer Research 37, 191-200. doi: 10.1007/BF00748937

Mosier AR, Doran JW, Freney JR (2002) Managing soil denitrification. Journal of Soil and Water Conservation 57, 505-513.

Nelson DW, Huber D (2001) Nitrification inhibitors for corn production. In 'National corn handbook (NCH-55)'. www.agcom.purdue.edu/AGCom/ Pubs/NCH/NCH-55.html

Oberle SL, Keeney DR (1990) Factors influencing corn fertilizer nitrogen requirements in the northern US corn belt. Journal of Production Agriculture 3, 527-534.

Pasda G, Hahndel R, Zerulla W (2001) Effect of fertilizers with the new nitrification inhibitor DMPP (3,4-dimethylpyrazole phosphate) on yield and quality of agricultural and horticultural crops. Biology and Fertility of Soils 34, 85-97 doi: 10.1007/s003740100381

Patra D, Kiran U, Kumar S (2002) Urease and nitrification inhibitors from natural source: Artemisia annua. Journal of the Indian Society of Soil Science 50, 508-510.

Patra DD, Kiran U, Pande P (2006) Urease and nitrification retardation properties in natural essential oils and their by-products. Communications in Soil Science and Plant Analysis 37, 1663-1673. doi: 10.1080/00103620600710306

Peoples MB, Freney JR, Mosier AR (1995) Minimizing gaseous losses of nitrogen. In 'Nitrogen Fertilization in the Environment'. (Ed. PE Bacon) pp. 565-602. (Marcel Dekker: New York)

Peoples MB, Boyer EW, Goulding KWT, Heifer P, Ochwoh VA, Vanlauwe B, Wood S, Yagi Y, Van Cleemput O (2004) Pathways of nitrogen loss and their impacts on human health and the environment. In 'Agriculture and the nitrogen cycle: Assessing the impacts of fertilizer use on food production and the environment'. (Eds AR Mosier, JK Syers, JR Freney) pp. 53-69. (Island Press: Washington, DC)

Prasad R, De Datta SK (1979) Increasing fertilizer efficiency in wetland rice. In 'Nitrogen and rice', pp. 465-484. (International Rice Research Institute: Los Banos, The Philippines)

Prasad R, Power JF (1995) Nitrification inhibitors for agriculture, health and the environment. Advances in Agronomy 54, 233-281.

Prasertsak P, Freney JR, Saffigna PG, Denmead OT, Prove BG (200 la) Fate of urea nitrogen applied to a banana crop in the wet tropics of Queensland. Nutrient Cycling in Agroecosystems 59, 65-73. doi: 10.1023/A: 1009806826141

Prasertsak P, Freney JR, Denmead OT, Saffigna PG, Prove BG (2001b) Significance of gaseous nitrogen loss from a tropical dairy pasture fertilized with urea. Australian Journal of Experimental Agriculture 41,625-632. doi: 10.1071/EA00131

Prasertsak P, Freney JR, Denmead OT, Saffigna PG, Prove BG, Reghenzani JR (2002) Effect of fertilizer placement on nitrogen loss from sugarcane in tropical Queensland. Nutrient Cycling in Agroecosystems 62, 229-239. doi: 10.1023/A:1021279309222

Rafii ZE, Evrard TO, Rockwell JC, Balty A (1984) Nitrification inhibition properties of etriidiazol. In 'Antimicrobials and agriculture'. (Ed. M Woodbine) pp. 45-62. (Butterworths: London)

Randall PJ, Freney JR, Hodgkin J, Morton TC (2002) Effect of acetylene generated from carbide on nitrification in soil, yield of irrigated maize and growth of maize seedlings. In 'Plant nutrition--food security and sustainability of agro-ecosystems. Proceedings XIV International Plant Nutrition Colloquium'. Hannover. (Eds WJ Horst et al.) pp. 774-775. (Kluwer Academic Publishers: Dordrecht, The Netherlands)

Rao SC (1996) Evaluation of nitrification inhibitors and urea placement in no-tillage winter wheat. Agronomy Journal 88, 904-908.

Rao SC, Popham TW (1999) Urea placement and nitrification inhibitor effects on growth and nitrogen accumulation in no-till winter wheat. Crop Science 39, 1115-1119.

Raun WR, Johnson GV (1999) Improving nitrogen use efficiency for cereal production. Agronomy Journal 91, 357-363.

Rochester IJ, Gaynor H, Constable GA, Saffigna PG (1994) Etridiazole may conserve applied nitrogen and increase yield of irrigated cotton. Australian Journal of Soil Research 32, 1287-1300. doi: 10.1071/ SR9941287

Rochester IJ, Constable GA, Saffigna PG (1996) Effective nitrification inhibitors may improve nitrogen and fertiliser recovery in irrigated cotton. Biology, and Fertility Soils 23, 1-6. doi: 10. 1007/BF00335810

Rodgers GA (1983) Effect ofdicyandiamide on ammonia volatilization from urea in soil. Fertilizer Research 4, 361-367. doi: 10.1007/BF01054009

Roy AH, Hammond LL (2004) Challenges and opportunities for the fertilizer industry. In 'Agriculture and the Nitrogen Cycle: Assessing the Impacts of Fertilizer Use on Food Production and the Environment'. (Eds AR Mosier, JK Syers, JR Freney) pp. 233-243. (Island Press: Washington, DC)

Scblegel AJ (1991) Reduced ammonia phytotoxicity from UAN solution by urease inhibitor N-(normal-butyl) Thiophosphoric Triamide. Journal of Fertilizer Issues 8, 40-44.

Schroeder JJ, Neeteson J, Oenema O, Struik PC (2000) Does the crop or the soil indicate how to save nitrogen in maize production? Reviewing the state of the art. Field Crops Research 66, 151-164. doi: 10. 1016/S03784290(00)00072-1

Serna MD, Banuts J, Quinones A, Primo-Millo E, Legaz F (2000) Evaluation of 3,4-dimethylpyrazole phosphate as a nitrification inhibitor in a Citrus-cultivated soil. Biology and Fertility of Soils 32, 41-46. doi: 10.1007/ s003740000211

Sharma SN, Kumar R (1998) Effects of dicyandiamide (DCD) blended with urea on growth, yield and nutrient uptake of wheat. The Journal of Agricultural Science 131, 389-394. doi: 10.1017/S002185969800598X

Sharma SN, Prasad R (1996) Use of nitrification inhibitors (neem and DCD) to increase N efficiency in maize-wheat cropping system. Fertilizer Research 44, 169-175. doi: 10.1007/BF00750923

Shaviv A (2000) Advances in controlled release fertilizers. Advances in Agronomy 71, 1-49.

Shaviv A (2005a) Controlled release fertilizers. In 'Proceedings of the IFA International Workshop on Enhanced Efficiency Fertilizers'. Frankfurt, Germany, 28-30 June 2005.

Shaviv A (2005b) Environmental friendly nitrogen fertilization. Science in China. Series C, Life Sciences 48, 937-947.

Shoji S (2005) Innovative use of controlled availability fertilizers with high performance for intensive agriculture and environmental conservation. Science in China. Series C, Life Sciences 48, 912-920.

Shoji S, Gandeza AT (1992) 'Controlled release fertilizers with polyolefin resin coating.' (Konno Printing Co. Ltd.: Sendai, Japan)

Shoji S, Kanno H (1994) Use of polyolefin-coated fertilizers for increasing fertilizer efficiency and reducing nitrate leaching and nitrous-oxide emissions. Fertilizer Research 39, 147-152. doi: 10.1007/BF00750913

Shoji S, Delgado J, Mosier A, Miura Y (2001) Use of controlled release fertilizers and nitrification inhibitors to increase nitrogen use efficiency and to conserve air and water quality. Communications in Soil Science and Plant Analysis 32, 1051-1070. doi: 10.1081/CSS-100104103

Simpson JR, Freney JR, Wetselaar R, Muirhead WA, Leuning R, Denmead OT (1984) Transformations and losses of urea nitrogen after application to flooded rice. Australian Journal o/" Agricultural Research 35, 189-200. doi: 10.1071/AR9840189

Simpson JR, Freney JR, Muirhead WA, Leuning R (1985) Effects of phenylphosphorodiamidate and dicyandiamide on nitrogen loss from flooded rice. Soil Science Society of America Journal 49, 1426-1431.

Singh J, Saggar S, Bolan NS (2004) Mitigating gaseous losses of nitrogen from pasture soil with urease and nitrification inhibitors. In 'SuperSoil 2004, 3rd Australian New Zealand Soils Conference'. University of Sydney, Australia. (CD-ROM)

Siva KB, Aminuddin H, Husni MHA, Manas AR (2000) Ammonia volatilization from urea as affected by humic substances derived from pahn oil mill effluent (POME) and tropical peat. Tropical Agriculture 77, 13 20.

Skiba U, Smith KA, Fowler D (1993) Nitrification and denitrification as sources of nitric oxide and nitrous oxide in a sandy loam soil. Biology and Fertility of Soils 25, 1527-1536.

Slangen JHG, Kerkhoff P (1984) Nitrification inhibitors in agriculture and horticulture: A literature review. Fertilizer Research 5, 1-76. doi: 10.1007/BF01049492

Smith CJ, Freney JR, Chalk PM, Galbally IE, McKenney DJ, Cai GX (1988) Fate of urea nitrogen applied in solution in furrows to sunflowers growing on a red-brown earth: Transformation, losses and plant uptake. Australian Journal of Agricultural Research 39, 793-806. doi: 10.1071/AR9880793

Smith CJ, Freney JR, Sherlock RR, Galbally IE (1991) The fate of urea nitrogen applied in a foliar spray to wheat at heading. Fertilizer Research 28, 129 138. doi: 10.1007/BF01049743

Smith KA, McTaggart IP, Tsuruta H (1997) Emissions of [N.sub.2]0 and NO associated with nitrogen fertilization in intensive agriculture, and the potential for mitigation. Soil Use and Management 13, 296-304. doi: 10.1111/j.1475-2743.1997.tb00601.x

Smith LC, Monaghan RM, Ledgard SF, Catto WD (2005) The effectiveness of different nitrification inhibitor formulations in limiting nitrate accumulation in a Southland pastoral soil. New Zealand Journal of Agricultural Research 48, 517-529.

Somda ZC, Mills HA, Phatak SC (1989) Effects of nitrapyrin, terrazole and simazine on soil nitrogen transformation and corn growth. Communications in Soil Science and Plant Analysis 20, 2177-2199.

Somda ZC, Phatak SC, Mills HA (1990) Nitrapyrin, terrazole, atrazine and simazine influence on denitrification and corn growth. Journal of Plant Nutrition 13, 1195-1208.

Strong WM, Saffigna PG, Copper JE, Cogle AL (1992) Application of anhydrous ammonia or urea during the fallow period for winter cereals on the Darling Downs, Queensland. 11. The recovery of [sup.15]SN by wheat and sorghum in soil and plant at harvest. Australian Journal of Soil Research 30, 711-721. doi: 10.1071/SR9920711

Takebe M, Sato N, Ishii K, Yoneyama T (1996) Effect of slow release nitrogen fertilizers on the contents of oxalic acid, ascorbic acid, sugars, and nitrate in spinach (Spinich oleracea L.). Soil Science and Plant Nutrition 67, 147-154.

Tomlinson TE (1970) Urea: agronomic applications. Proceedings of the Fertilizer Society 113, 1-76.

Trenkel ME (1997) 'Controlled release and stabilized fertilizers in agriculture.' (International Fertilizer Industry Association: Paris)

Vallejo A, Diez JA, Valdivia LML, Gasco A, Jimenez C (2001) Nitrous oxide emission and denitrification nitrogen losses from soils treated with isobutylenediurea and urea plus dicyandiamide. Biology and Fertility of Soils 34, 248-257. doi: 10.1007/s003740100409

Vallejo A, Garcia-Torres L, Diez JA, Arce A, Lopez-Fernandez S (2005) Comparison of N losses (N[O.sub.3] , [N.sub.2]O, NO) from surface applied, injected or amended (DCD) pig slurry of an irrigated soil in a Mediterranean climate. Plant and Soil 272, 313-325. doi: 10. 1007/s111104-004-5754-3

Varel VH (1997) Use of urease inhibitors to control nitrogen loss from livestock waste. Bioresource Technology 62, 11-17. doi: 10.1016/ S0960-8524(97)00130-2

Varel VH, Nienaber JA, Freetly HC (1999) Conservation of nitrogen in cattle feedlot waste with urease inhibitors. Journal of Animal Science 77, 1162-1168.

Wagner-Riddle C, Thurtell GW (1998) Nitrous oxide emissions from agricultural fields during winter and spring thaw as affected by management practices. Nutrient Cycling in Agroecosystems 52, 151-163. doi: 10.1023/A:1009788411566

Wang XJ, Douglas L (1996) Effect of phosphoroamides on soil urease activity, and plant dry matter production and N uptake by wheat plants. Agrochimica 40, 209-215.

Wang WM, Shi YX, Liu H (2005) Effects of controlled-release nitrogen fertilizers on yield and quality of Chinese cabbage (Brassica campestris L. ssp. Pekinensis). In 'Proceedings of the 3rd International Nitrogen Conference.' (Eds ZL Zhu, K Minami, GX Xing) pp. 405-410. (Science Press: Beijing)

Watson CJ (2000) 'Urease activity and inhibition--principles and practice.' Proceedings No. 454. (The International Fertiliser Society: York, UK)

Watson CJ (2005) Urease iinhibitors. In "IFA International Workshop on Enhanced Efficiency Fertilizers'. Frankfurt, Germany, 28-30 June 2005.

Watson CJ, Miller H, Poland P, Kilpatrick DJ, Allen MDB, Garrett MK, Christianson CB (1994a) Soil properties and the ability of the urease inhibitor N-(n-butyl) thiophosphoric triamide (nBTPT) to reduce ammonia volatilization from surface-applied urea. Soil Biology & Biochemistry 26, 1165-1171. doi: 10.1016/0038-0717(94)90139-2

Watson CJ, Poland P, Miller H, Allen MBD, Garrett MK, Christianson CB (1994b) Agronomic assessment and 15N recovery of urea amended with the urease inhibitor nBTPT (N-(n-butyl) thiophosphoric triamide) for temperate grassland. Plant and Soil 161, 167-177. doi: 10.1007/ BF00046388

Weiske A, Benckiser G, Ottow JCG (2001a) Effect of the new nitrification inhibitor DMPP in comparison to DCD on nitrous oxide ([N.sub.2]O) emissions and methane (C[H.sub.4]) oxidation during 3 years of repeated applications in field experiments. Nutrient Cycling in Agroecosystems 60, 57-64. doi: 10.1023/A: 1012669500547

Weiske A, Benckiser G, Herbert T, Oltow JCG (2001b) Influence of the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) in comparison to dicyandiamide (DCD) on nitrous oxide emissions, carbon dioxide fluxes and methane oxidation during 3 years of repeated application in field experiments. Biology and Fertility of Soils 34, 109-117. doi: 10.1007/s003740100386

Wolt JD (2004) A meta-evaluation of nitrapyrin agronomic and environmental effectiveness with emphasis on corn production in the Midwestrn USA. Nutrient Cycling in Agroecosystems 69, 23-41. doi: 10.1023/B:FRES.0000025287.52565.99

Wood AW (1991) Management of crop residues following green harvesting of sugarcane in north Queensland. Soil and Tillage Research 20, 69-85. doi: 10.1016/0167-1987(91)90126-1

Wu ZJ, Zhang HJ, Zhou LK, Li RH, Xie HT, Shoji S (2005) Effects of Meister controlled release fertilizer on dynamics of soil mineral N, and yields and quality of crops in China. In 'Proceedings of the 3rd International Nitrogen Conference'. (Eds ZL Zhu, K Minami, GX Xing) pp. 399-404. (Science Press: Beijing)

Xu XK, Boeckx P, van Cleemput O, Kazuyuki I (2005) Mineral nitrogen in a rhizosphere soil and in standing water during rice (Oryza sativa L.) growth: effect of hydroquinone and dicyandiamide. Agriculture. Ecosystems & Environment 109, 107-117. doi: 10.1016/j. agee.2005.02.010

Zerulla W, Barth T, Dressel J, Erhardt K, von Locquenghien KH, Pasda G, Radle M, Wissemeier AH (2001) 3,4-Dimethylpyrazole phosphate (DMPP)--a new nitrification inhibitor for agriculture and horticulture. Biology and Fertility of Soils 34, 79-84. doi: 10.1007/ s003740100380

Zhang SL, Cai GX, Wang XZ, Xu YH, Zhu ZL, Freney JR (1992) Losses of urea-nitrogen applied to maize grown on a calcareous fluvo-aquic soil in north China plain. Pedosphere 2, 171-178.

D. Chen (A, D), H. Suter (A), A. Islam (A), R. Edis (A), J. R. Freney (A, B), and C. N. Walke (C)

(A) School of Resource Management, Faculty of Land and Food Resources, The University of Melbourne, Vic. 3010, Australia.

(B) CSIRO Plant Industry, GPO Box 1600, Canberra, ACT 2601, Australia.

(C) Incitec Pivot Ltd, PO Box 54, North Geelong, Vic. 3215, Australia.

(D) Corresponding author. Email: delichen@unimelb.edu.au
Table 1. Fertiliser nitrogen used for crops and pasture in Australia
in 2000 (FAO, IFA, IFDC, IPI, PPI 2002)

 Fertiliser consumption Application rate
Commodity (Gg N) (kg N/ha)

Cereals 702 42.9
Sugarcane 96 229.1
Pasture 75 2.5
Horticulture 71 187.8
Cotton 56 121.2
Oilseeds 55 12.8
Total 1055

Table 2. Recovery of fertiliser nitrogen by crops and
pastures in Australia

 Recovery (% of applied)

Crop and location Plant Soil Plant + soil

Bananas: East Palmerston, Qld 15 60 75
Cotton (irrigated): Narrabri, NSW 27-29 8-28 8-57

Pasture: Millaa Millaa, Qld 42 18 60
Rice (flooded): Griffith, NSW 6-17 37-18 44-60

Sugarcane:
 Mackay, Qld 14-38 23-41 38-61
 South Johnstone, Qld 19-29 22-25 41-54
Sunflowers: Tatura, Vic. 35 30 65
Wheat (dryland): Hanwood, Murrami, 22-59 20-54 60-88
 Widgelli, Willurah, Wumbulgal,
 Yanco, NSW; Birchip, Chinkapook,
 Elmore, Wunghnu, Diggers Rest,
 Vic.
Wheat (irrigated): Tatura, Vic. 25 25 50

Crop and location References

Bananas: East Palmerston, Qld Prasertsak et al. (2001a)
Cotton (irrigated): Narrabri, NSW Freney et al. (1993),
 Humphreys et al. (1990)
Pasture: Millaa Millaa, Qld Prasertsak et al. (2001 b)
Rice (flooded): Griffith, NSW Simpson et al. (1984, 1985),
 Keerthisinghe et al. (1993)
Sugarcane:
 Mackay, Qld Chapman et al. (1991)
 South Johnstone, Qld Prasertsak et al. (2002)
Sunflowers: Tatura, Vic. Smith et al. (1988)
Wheat (dryland): Hanwood, Murrami, Bacon and Freney (1989),
 Widgelli, Willurah, Wumbulgal, P. E. Bacon, J. R. Freney,
 Yanco, NSW; Birchip, Chinkapook, unpublished data
 Elmore, Wunghnu, Diggers Rest,
 Vic.
Wheat (irrigated): Tatura, Vic. Freney et al. (1992a)

Table 3. Nitrogen lost from agricultural systems in
Australia (% of applied)

Crop and location Loss

 Volatilised Denitrified Total

Bananas: East Palmerston, Qld 20 5 25
Cotton (irrigated): Narrabri, NSW 0 43-92 43-92
Pasture:
 Millaa Millaa, Qld 20 20 40
 Ellinbank, Vic. 32-57 13-15 47-70
Rice (flooded): Griffith, NSW 0-11 15-56 40-56
Sugarcane:
 Mackay, Qld 0 39-62 39-62
 South Johnstone, Qld 6-37 22-40 46-59
Sunflowers: Tatura, Vic. 6 29 35
Wheat (dryland): Hanwood, Murrami, 1-24 2-27 12-40
 Widgelli, Willurah, Wumbulgal,
 Yanco, NSW; Birchip, Chinkapook,
 Elmore, Wunghnu, Diggers Rest,
 Vic.
Wheat (irrigated): Tatum, Vic. 0 50 50

Crop and location References

Bananas: East Palmerston, Qld Prasertsak et al. (2001a)
Cotton (irrigated): Narrabri, NSW Freney et al. (1993),
 Humphreys et al. (1990)
Pasture:
 Millaa Millaa, Qld Prasertsak et al. (20016)
 Ellinbank, Vic. Eckard et al. (2003)
Rice (flooded): Griffith, NSW Simpson et al. (1984, 1985),
 Keerthisinghe et al. (1993)
Sugarcane:
 Mackay, Qld Chapman et al. (1991)
 South Johnstone, Qld Prasertsak et al. (2002)
Sunflowers: Tatura, Vic. Smith et al. (1988)
Wheat (dryland): Hanwood, Murrami, Bacon and Freney (1989),
 Widgelli, Willurah, Wumbulgal, P. E. Bacon, J. R. Freney,
 Yanco, NSW; Birchip, Chinkapook, unpublished data
 Elmore, Wunghnu, Diggers Rest,
 Vic.
Wheat (irrigated): Tatum, Vic. Freney et al. (1992a)

Table 4. Compounds produced commercially as nitrification inhibitors
(modified from Nelson and Huber 2001)

 Common or
Chemical name trade name Manufacturer

2-Chloro-6-(trichloromethyl)- Nitrapyrin, N-Serve Dow Chemical Co.
 pyridine
5-Ethoxy-3-trichloromethyl-I, Dwell, Terrazole, Uniroyal
 2, 4-thiadiazol Etradiazo) Chemical
Dicyandiamide DCD SKW Trostberg AG
3,4-Dimethylpyrazole phosphate DMPP (ENTEC) BASF AG
2-Amino-4-chloro-6-methyl- AM Mitsui Toatsu
 pyrimidine Co.
2-Mercapto-benzothiazole MBT Onodo Chemical
 Industries
2-Sulfanilamidothiazole ST Mitsui Toatsu
 Co.
Thiourea TU Nitto Ryuso
COPYRIGHT 2008 CSIRO Publishing
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 2008 Gale, Cengage Learning. All rights reserved.

Article Details
Printer friendly Cite/link Email Feedback
Author:Chen, D.; Suter, H.; Islam, A.; Edis, R.; Freney, J.R.; Walke, C.N.
Publication:Australian Journal of Soil Research
Article Type:Report
Geographic Code:8AUST
Date:Jun 1, 2008
Words:12439
Previous Article:Short-term effects of wheat straw incorporation into paddy field as affected by rice transplanting time.
Next Article:Salmonella uptake in sheep exposed to pastures after biosolids application to agricultural land.
Topics:


Related Articles
Nitrogen fertilizer saps veggies' vitamin C.
The allocative efficiency of material input use in Russian agriculture.
Effects of nitrogen fertiliser and wheat straw application on C[H.sub.4] and [N.sub.2]O emissions from a paddy rice field.
Key crop nutrient management issues in the Western Australia grains industry: a review.
Identifying fertiliser management strategies to maximise nitrogen and phosphorus acquisition by wheat in two contrasting soils from Victoria,...
Wheat roots proliferate in response to nitrogen and phosphorus fertilisers in Sodosol and Vertosol soils of south-eastern Australia.

Terms of use | Privacy policy | Copyright © 2020 Farlex, Inc. | Feedback | For webmasters