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Effect of biosolids on the organic matter content and phosphorus chemical fractionation of heated volcanic Chilean soils.

Introduction

Soils derived from volcanic materials constitute approximately 70% of arable land in central-southern Chile. These soils are rich in iron oxides, with high phosphate retention, a variable charge dependent on pH and ionic strength, and high organic matter (OM) accumulation due to complexation of humic components with aluminium release by alteration of volcanic components (Besoain 1999).

On the other hand, in Andisols and Ultisols from the south of Chile, the OM consists of about 60-75% humic acids, with structural functional groups with a high chelating capacity to immobilise nutrients which are gradually available to plants. They also represent a source of carbon for microbiological activity (Mora and Canales 1995).

In general, soil OM levels depend on the interaction between input and decomposition rates, which are controlled by factors such as climate, soil properties, drainage, and land use. In situ stabilisation and destabilisation mechanisms slow down or accelerate turnover rates (Matus et al. 2006).

Organic matter content is related to several soil properties such as complexation, macro- and micronutrient reservoirs, cation exchange capacity, microorganism population, chemical and physical properties, and OM interaction with components such as N, P, and S (Besoain and Sepulveda 1985; Alloway 1990). The OM content of Chilean soils ranges from 4 to 36% in surface horizons (Galindo et al. 1992). Soil properties such as active/free iron oxide ratio, isoelectric point (IEP), cation exchange capacity (CEC), and potassium-calcium cation exchange equilibrium have been related to OM content in Chilean volcanic soils. An inhibitory effect of OM on iron oxide crystallisation has been observed, the IEP of Andisols increases as OM decreases, and that relationship can be used to follow soil OM degradation. In Andisols the organic fraction is mostly responsible for negative surface charge generation when soil pH increases, through the ionisation of active carboxylic and phenolyc surface groups (Escudey et al. 2004a).

In southern Chile, from October 2005 until May 2006, more than 5300 forest fires occurred, involving around 20 000 ha of pine and eucalyptus plantations and native forests, averaging about 3.6 ha per forest fire (Conaf 2007). It has been reported that heating soils at 400[degrees]C may lead to the destruction of OM (Antilen et al. 2006a), and in forest fires temperatures >700[degrees]C have been reported (Mendoza 1986), which may result in the total destruction of OM in the top 0.05-m soil layer (Antilen et al. 2006a). In relation to total P content, different reports have shown a high total P content in agricultural soils (1000-3000mg/kg), even in unfertilised soils. In most soils, organic P represents >50% of total P, mainly as inosytol penta-and hexaphosphates linked to Fe and/or Al (Bode and Rubio 2003). The high fixation of phosphate in allophanic soils is perhaps one of the most important problems in their agronomic use. Phosphate retention in these soils is mainly due to the ability of amorphous aluminium silicate clay to strongly adsorb the phosphate, mainly by ligand-exchange mechanisms (Parfitt 1980).

Accumulation of P will depend on fertiliser application rate, years of application, the adsorptive capacity of soil matrix surfaces, and microbial activity, especially microorganisms involved in P cycling (Borie and Rubio 2003). When P is applied to soils, >90% is not taken up by crops in the first year, and is retained in insoluble or fixed forms by colloidal surfaces in the soil (Stevenson and Cole 1999).

The growing scarcity of organic matter and the low P availability in agricultural soils as a result of adverse climatic conditions and inadequate soil management practices, including forest fires, has led to the search for replacements for these sources (Englande and Reimers 2001; Marche et al. 2003; Dinel et al. 2005; Raviv et al. 2005). Biosolids can be a source of OM and P, because the organic fraction constitutes around 50% of the total solids, while total P content is around 10-20 kg/t, so the application is an excellent way for recycling biosolid nutrients such as P, N, and K. This practice is one of the most promising ways for reclaiming degraded soils in some European countries (Sanchez-Monedero et al. 2004) where many soils are badly degraded as a result of repeated forest fires (Lopez-Bermudez and Albadalejo 1990).

The application of biosolids on land has been reported to have positive effects on fertility, crop yields (Gardiner et al. 1995; Jorba and Andres 2000), and changes in chemical, physical, biological, and microbial properties (Selivanovskaya and Latypova 2006; Vaca-Paulin et al. 2006). The organic components in biosolids provide several non-specific and specific sorption sites for metals from which they may be difficult to displace (Shuman 1999), decreasing their bioavailability in degraded soils (Gao et al. 2003).

Application of biosolids should be considered when replacing the OM lost during forest fires. The objective of this research was therefore to evaluate through incubation studies the impact of biosolids on OM and P chemical fractionation for reclaiming heated soils derived from volcanic materials.

Materials and methods

Soil and biosolids description

Soil samples were collected from a depth of 0-0.15 m from uncultivated areas of Ralun (Andisol), Diguillin (Inceptisol), and Collipulli (Ultisol), in southern Chile. All samples were air-dried and sifted through 2mm. Biosolids were obtained from a domestic wastewater treatment plant with primary treatment near the city of Santiago, in central Chile. A detailed description and characterisation of all samples is presented in Table 1.

Soil incubation procedure

Five different treatments for each soil were studied with 2 replicates; control soil (C); soil heated at 200[degrees]C (T1) and 400[degrees]C (T2); soil at heated 200[degrees]C and 400[degrees]C and then amended with biosolids (T3 and T4), respectively.

To simulate the heat impact of fire, all soil samples were placed in layers 2-3 cm thick in a furnace for 40 min to assure homogeneous heating at 200[degrees]C or 400[degrees]C (Antilen et al. 2006b). Soil temperature during heating was measured by a type K Ni-Cr thermocouple. Biosolids were added to each heated soil in the amount needed to recover the OM lost after heating at 200[degrees]C or 400[degrees]C, considering a depth of 10mm per ha. The rates of biosolids were variable, where the values for T3 and T4 for Collipulli soil were 1.8 and 11.7 t/ha; for Ralun soil 3.2 and 33.1t/ha; and for Diguillin 2.7 and 22.6t/ha, respectively. The soils subjected to the different treatments were packed into pots with the same bulk density determined for undisturbed soil, after adding the corresponding amounts of biosolids. The total mass of undisturbed soil needed to fill the pot was weighed and the same amount of sifted soil + biosolids was packed and wetted to 50% of its water-holding capacity. The wetted soils were incubated at room temperature (25 [+ or -] 3[degrees]C) and weighed weekly. Double-distilled water was added to bring the soils up to 50% of their water-holding capacity (Klute 1965). The incubated pots were sampled after 2 and 4 months. Control soils with no incubation time were also analysed.

Chemical characterisation

Control soils, biosolids, and treated soils, before and after incubation, were analysed for pH (1:2.5 soil: water ratio), EC, and OM content based on the Walkley-Black method, modified to Chilean volcanic soils, which is in close agreement with the dry combustion method ([R.sup.2]=0.853 with n = 60), exchangeable cations (Sadzawka 1991), and total C and N content (elemental analysis). The bulk density, total porosity (Blake 1965), isoelectric point (Escudey et al. 1988; Galindo et al. 1992), and mineralogy of the control soils were also determined.

Chemical P fractionation in organic (humic and fulvic P) and inorganic P was determined by the sequential extraction procedure proposed by Steward and Oades (1972) modified by Borie and Zunino (1983). Briefly, 1.5 g of soil was extracted with 15 mL of 1 mol HCl/L, and the solid was then separated by centrifugation. Three successive alkaline extractions were carried out using 25, 15, and 15mL, respectively, of 0.5mol NaOH/L, to obtain the acid-extractable P fraction, where inorganic P was determined. Total P content from the acid and alkaline extracts was determined after destruction of the OM with NaBrO (Dick and Tabatabai 1977). Organic P in the acid extract (fulvic P) and the alkaline extract (humic P) was considered as the difference between total and inorganic P. Total inorganic P corresponds to the sum of the inorganic P in the acid and alkaline extracts. Total organic P corresponds to the sum of the fulvic and humic P. Total extracted P (designated as total P) corresponds to the sum of total inorganic and total organic extracted P (Briceno et al. 2006). Available P forms were also determined by the Olsen P procedure adapted to Chilean volcanic soils (Sadzawka 1991), with NaHC[O.sub.3] solution. In all the samples phosphorus in solution was determined by the sulfomolybdic acid method using ascorbic acid as the reducing agent (Murphy and Riley 1962; Dick and Tabatabai 1977).

Results and discussion

Chemical characterisation

Soil and biosolids characterisation is presented in Table 1. The OM content in Ralun (Andisol) and Diguillin (Inceptisol) was greater than in Collipulli (Ultisol), but all 3 soils can be classified as of medium to high OM content. Soil OM was related to mineralogy dominated by low crystallinity compounds such as allophane present in Ralun and Diguillin, where halloysite and vermiculite are also present less significantly. The biosolids have about 3 times the Walkley-Black OM content of the soils, making them a valuable organic amendment.

While the pH was acidic for all soils, the pH of biosolids was close to neutral. The exchangeable cations of the biosolids were 8-29 times higher than those of the soils, mainly due to the high Ca content as a result of the addition of calcium carbonate at the end of the biosolids treatment process. The EC of the biosolids was 6-19 times higher than that of the soils, in agreement with the exchangeable cations values. The IEP of the biosolids was almost 4 pH units higher than that of the soils.

Total P followed the sequence Collipulli < Ralun < Diguillin, while total P content in the biosolids was about 6-18 times greater than in the soils. The total P content determined in the biosolids is the habitual amount from samples originating in wastewater treatment plants, with around 90% as inorganic P (Wong et al. 2001; Escudey et al. 2004b; Jensen and Jepsen 2005; Antilen et al. 2006b). Therefore, the addition of biosolids to soils may help reclaim the OM content, with some other consequences such as increased soil pH, while the high total Ca and P content could cause important changes in the magnitude and sign of variable soil surface charge. These changes would be due not only to changes in pH and ionic strength, but also to the presence of Ca and phosphate, which are specifically adsorbed on volcanic soils (Antilen et al. 2000).

Soil incubation studies

In general, pH increased in all heated samples and in soils treated with biosolids, compared with the control soils (Table 2). The pH changes seen in Ralun and Diguillin after heating at 400[degrees]C were probably related to OM content and decomposition processes.

In heated samples T1 and T2, the pH increased slightly with an incubation time of 2 months, except for Collipulli T2, Ralun T1, and Diguillin T1, whose pH values remained constant. Later, after 4 months, the opposite effect was observed in amended soils, indicating the ability of the soil to buffer pH, with the exception of Ralun T2 and Diguillin T1. It is probable that for these 2 exceptions, longer incubation times are necessary to reach the same performance. However, for soils treated with biosolids after 4 months (T3 and T4), all the samples showed the same behaviour, decreasing their pH values. This well-known buffer behaviour of volcanic soils can be associated to previously adsorbed heavy metals release processes, because the negative surface charge and cation exchange capacity decrease when soil pH decreases (Antilen et al. 2006b). EC changes were seen when comparing the different treatments (Table 2), with an important increase occurring between T1 and T2, which could be related to the fact that most of the OM loss occurred between 200[degrees]C and 400[degrees]C. After that, the amended heated soils showed increasing EC, more significant in T4 than in T3, due to ion release from the biosolids.

Incubation time was not a significant variable to increase the EC in heated soils, with some exceptions in the Ralun soil, while in the amended heated soils, although there were increases, they were not important. In relation to exchangeable cations, an increase was seen with biosolids amendment compared with the control and heated soils, with no incubation time effect.

Therefore, the addition of biosolids increases EC and exchangeable cations as a result of a continuous slow delivery of ionic species from the biosolids (mainly Ca species), controlled by their solubility constants. In relation with OM content and temperature effect, most changes occurred between 200[degrees]C and 400[degrees]C (Table 2), where decarboxylation, dehydrogenation, and dehydroxylation processes have been reported (Galindo et al. 1987), all leading to OM loss.

In addition to observed soil changes, there is evidence that black carbon, obtained from an incomplete combustion, could contribute to stable humus in the soil environment (Brodowski et al. 2007). Therefore, is interesting to note that during Ralun, Diguillin, and Collipulli heating experiments, the presence of black carbon has been assumed from diffuse reflectance measurements carried out between 400 and 800 nm (M. Escudey, unpublished results). Soil reflectance increases when temperature increases because soil colour becomes lighter. However, when heated at 200[degrees]C, a temperature where only a fraction of the original OM content has been affected by heat, soil reflectance is lower than the value observed in soils heated at 100[degrees]C. This behaviour could be due to the presence of black carbon, which absorbs visible radiation, and consequently a reduction of reflectance occurs.

[FIGURE 1 OMITTED]

OM destruction resulted not only in a loss of active sites, but also in the exposure of active inorganic surface sites such as Al-OH and Fe-OH with [pK.sub.a] higher than that of carboxylic or phenolyc groups. Consequently, a positive surface charge at the equilibrium pH (Galindo et al. 1987) should have resulted in increased sorption of anionic species from the biosolids. With the exception of Ralun heated at 400[degrees]C, incubation time caused no significant changes in OM. These results agree with studies in burnt volcanic soils of Patagonia (Argentina) that showed a 52% decrease in OM content even 4 years after forest fire (Alauzis et al. 2004). In Ralun soil, OM content decreased from 11.7 to 1.7 mg/kg after heating at 400[degrees]C, but it increased to 3.5 mg/kg after 4 months of incubation. This result may be related to the measurement of respiration activity of soil biomass in heated soils at 200[degrees]C (Antilen et al. 2001), where C[O.sub.2] evolution after 6 days of incubation showed an important increase over that of soils heated at 110[degrees]C. Therefore, the increase in metabolic activity can be the consequence of partial OM degradation during the heating processes.

Between 45 and 65% of total P in control soils was present as organic P, associated mostly with humic acids (Fig. 1). In this organic fraction, chemical P forms such as diester P have been reported, which is easily biodegradable in the soil and is associated with high OM content (Escudey et al. 2004b). As a result of the thermal treatment, 4-23% of organic P was turned into inorganic P in soils heated at 200[degrees]C, and 26-44% in soils heated at 400[degrees]C. The main inorganic P form was orthophosphate with the presence of pyrophosphate (Escudey et al. 2001, 2004c).

In biosolids, only 9.8% (1000 mg/kg) of total P (10 200 mg/kg) was present as organic P. Approximately 80% (800 mg/g) of this organic P was associated with fulvic acids and 20% (200mg/g) with humic acids. For available P, only 0.1% (183mg/kg) of total P was determined as Olsen P. More importantly, about 88-96% of the P in biosolids-treated soils was inorganic in T4, but only about 55-75% in T3. These results show that amendment with biosolids increased the accumulation of inorganic P in relation to the biosolids added to each soil (Fig. 1).

The distribution of P forms showed little difference with incubation time (4 months), indicating that after a short time, biosolids P was not significantly transformed into organic P, which is more available for plants in volcanic soils. However, the results of Olsen P (Table 3) showed the increase of available P in T3 and T4, with no incubation time effect in comparison with control soils. In the control soils, Olsen P was higher in Ralun and Diguillin than in Collipulli soil, with no significant variation with incubation time, with the exception of T2 where Olsen P decreased with the incubation time. These results, in connection with temperature applied (400[degrees]C), may suggest some influence of biological activity on the immobilisation of this available P, considering the increase in metabolic activity after thermal impact, measured with the incubation time (Antilen et al. 2001). This justification is consistent with results of Akhtar et al. (2002), where biologically available P was determined.

In relation to these results, inorganic P accumulation can be explained because most of the biosolids P can be bound as Ca phases, considering that lime was added, and the Ca phases may be related to the HCl extraction step. As a consequence of biosolids amendment, an increase in total P was seen in the soil, and the effect was positive in terms of increased P availability to plants. This analysis can be supported with the results of Olsen P from biosolids, control soils, heated soils, and biosolids-treated soils after 2 and 4 months of incubation (Table 3).

Conclusions

Heating resulted in increased pH, EC, exchangeable cations, and inorganic P, but decreased OM compared with control soils. The pH changes seen with temperature and biosolids amendment can be considered beneficial to soils derived from volcanic materials, due to their acidic characteristics, which may result in aluminium toxicity problems. However, pH decreased with incubation time (4 months) to initial pH values (0 months), showing the buffer capacity of volcanic soils. The increase of EC in amended soils will not result in a salinity problem due to the high precipitation in the region where the soils are located.

Incubated soils heated at 400[degrees]C showed a natural OM recovery, which may be associated with a high metabolic activity after heating.

A significant proportion of the organic P (fulvic and humic P) was turned into inorganic P by heating, and no incubation time effects were found for this component. The inorganic P increased significantly in amended soils, probably because it is bound to biosolid Ca-P phases and is strongly fixed in volcanic soils and not easily available for plants. It will be accumulated and could potentially contribute to soil and water pollution.

From these experimental data it can be concluded that biosolids are a valid short-range option for recovering organic matter loss and adding available P in soils affected by forest fires.

Acknowledgments

This study was supported by Project Limite 2007 VRAID-PUC, and by FONDECYT under Project 1030778.

Manuscript received 6 September 2007, accepted 23 May 2008

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Monica Antilen (A,D), Margarita Briceno (B), Gerardo Galindo (c), and Mauricio Escudey (c)

(A) Pontificia Universidad Catoloca de Chile, Facultad de Quimica, Vicuna Mackenna 4860, Santiago 6904411, Chile.

(B) Universidad Arturo Prat, Av. Arturo Prat 2120 Casilla 12, Iquique, Chile.

(C) Universidad de Santiago de Chile, Av. B. O'Higgins 3363, Santiago 7254758, Chile.

(D) Corresponding author. Email: mantilen@uc.cl
Table 1. Characterisation of soil and biosolids samples

n.d., Not determined

Characteristics Collipulli Ralun

Soil Order/source Ultisol Andisol

Soil Class Fine, mixed, Medial, mesic,
 thermic typic Acrudoxic Hapludands
 Rhodoxeralf

Latitude, longitude 36[degrees]58'S, 41[degrees]32'S,
 72[degrees]09'W 73[degrees]05'W

Altitude (m) 120-400 600-1400

Rainfall (m/year) 1.2-1.5 4.0-5.0

Mean annual temp. 15.8 10.5
([degrees]C)

Bulk density (g/mL) 1.24 0.90

EC (mS/cm) 0.1 [+ or -] 0.0 0.3 [+ or -] 0.0

Isoelectric point 2.65 2.75

Organic matter (wt%) 3.1 [+ or -] 0.0 11.7 [+ or -] 0.0

Total P (mg/kg) 576 [+ or -] 15 901 [+ or -] 36

pH ([H.sub.2]O 1:2.5) 5.4 [+ or -] 0.0 5.3 [+ or -] 0.0

C (%) 2.33 9.83

N (%) 0.20 0.74

C/N 11.15 13.23

Exch. cations 7.8 [+ or -] 0.1 3.0 [+ or -] 0.1
(cmol/kg)

 Na 0.1 0.1

 K 0.1 0.1

 Ca 5.2 2.4

 Mg 2.5 0.5

Mineral. comp. >50% Kaolinite Allophane

Total porosity (%) 50 61

Characteristics Diguillin Biosolids

Soil Order/source Inceptisol Water treatment
 plant

Soil Class Medial, thermic, Solid waste
 Humic Haploxerand

Latitude, longitude 36[degrees]53'S, 33[degrees]10'S,
 72[degrees]10'W 70[degrees]45'W

Altitude (m) 120-180 500-000

Rainfall (m/year) 1.2-1.8 0.3-0.4

Mean annual temp. 15.5 14.5
([degrees]C)

Bulk density (g/mL) 0.86 n.d.

EC (mS/cm) 0.2 [+ or -] 0.1 1.9 [+ or -] 0.1

Isoelectric point 2.80 6.40

Organic matter (wt%) 10.0 [+ or -] 0.0 31.0 [+ or -] 0.9

Total P (mg/kg) 1758 [+ or -] 89 10200 [+ or -] 35

pH ([H.sub.2]O 1:2.5) 5.1 [+ or -] 0.0 6.9 [+ or -] 0.2

C (%) 7.30 n.d.

N (%) 0.61 n.d.

C/N 11.95 n.d.

Exch. cations 10.3 [+ or -] 0.7 87.0 [+ or -] 1.1
(cmol/kg)

 Na 0.1 3.8

 K 0.7 1.1

 Ca 8.1 78.8

 Mg 1.5 4.1

Mineral. comp. >50% Allophane n.d.

Total porosity (%) 64 n.d.

Table 2. Organic matter content, pH, electric conductivity, and
exchangeable cations in amended soil samples (0), and after 2
and 4 months of incubation

 Organic matter (mg/kg)

Sample 0 2 4

Collipulli
C 3.1 [+ or -] 0.0 3.1 [+ or -] 0.0 3.1 [+ or -] 0.0
T1 2.8 [+ or -] 1.0 2.6 [+ or -] 0.1 2.8 [+ or -] 0.0
T2 0.7 [+ or -] 0.0 0.7 [+ or -] 0.0 0.7 [+ or -] 0.0
T3 3.1 [+ or -] 1.0 2.9 [+ or -] 0.2 3.4 [+ or -] 0.1
T4 3.1 [+ or -] 0.0 4.0 [+ or -] 0.2 3.8 [+ or -] 0.2

Ralun
C 11.7 [+ or -] 0.0 11.9 [+ or -] 0.0 11.9 [+ or -] 1.0
T1 9.1 [+ or -] 1.0 9.8 [+ or -] 1.0 10.5 [+ or -] 0.0
T2 1.7 [+ or -] 0.0 4.0 [+ or -] 1.0 3.4 [+ or -] 0.0
T3 11.9 [+ or -] 1.0 11.4 [+ or -] 0.0 13.6 [+ or -] 0.0
T4 11.9 [+ or -] 0.0 13.8 [+ or -] 3.0 12.7 [+ or -] 3.0

Diguillin
C 10.0 [+ or -] 0.0 10.0 [+ or -] 0.0 10.0 [+ or -] 0.0
T1 9.1 [+ or -] 0.5 10.2 [+ or -] 0.0 9.8 [+ or -] 0.2
T2 2.9 [+ or -] 0.2 4.1 [+ or -] 0.2 3.6 [+ or -] 0.1
T3 10.0 [+ or -] 0.2 10.9 [+ or -] 0.1 10.5 [+ or -] 0.0
T4 10.0 [+ or -] 0.0 11.0 [+ or -] 0.2 10.9 [+ or -] 0.1

 pH

Sample 0 2 4

Collipulli
C 5.40 [+ or -] 0.01 5.46 [+ or -] 0.02 5.36 [+ or -] 0.01
T1 6.10 [+ or -] 0.01 6.14 [+ or -] 0.02 5.89 [+ or -] 0.01
T2 6.01 [+ or -] 0.02 6.01 [+ or -] 0.03 5.79 [+ or -] 0.01
T3 6.05 [+ or -] 0.01 6.04 [+ or -] 0.02 5.91 [+ or -] 0.02
T4 6.51 [+ or -] 0.03 6.61 [+ or -] 0.02 6.20 [+ or -] 0.01

Ralun
C 5.30 [+ or -] 0.01 5.32 [+ or -] 0.01 5.44 [+ or -] 0.02
T1 6.58 [+ or -] 0.02 6.59 [+ or -] 0.02 5.97 [+ or -] 0.03
T2 6.40 [+ or -] 0.01 6.47 [+ or -] 0.02 6.48 [+ or -] 0.02
T3 6.32 [+ or -] 0.03 6.36 [+ or -] 0.03 5.77 [+ or -] 0.01
T4 6.90 [+ or -] 0.01 6.94 [+ or -] 0.03 6.81 [+ or -] 0.01

Diguillin
C 5.10 [+ or -] 0.00 5.06 [+ or -] 0.01 5.10 [+ or -] 0.01
T1 5.55 [+ or -] 0.02 5.68 [+ or -] 0.01 5.84 [+ or -] 0.02
T2 6.65 [+ or -] 0.01 6.71 [+ or -] 0.02 5.96 [+ or -] 0.01
T3 5.88 [+ or -] 0.02 5.78 [+ or -] 0.01 5.50 [+ or -] 0.03
T4 6.58 [+ or -] 0.01 6.60 [+ or -] 0.01 6.51 [+ or -] 0.02

 Electric conductivity (mS/cm)

Sample 0 2 4

Collipulli
C 0.08 [+ or -] 0.01 0.08 [+ or -] 0.01 0.08 [+ or -] 0.00
T1 0.10 [+ or -] 0.00 0.11 [+ or -] 0.00 0.12 [+ or -] 0.01
T2 0.16 [+ or -] 0.01 0.17 [+ or -] 0.01 0.29 [+ or -] 0.00
T3 0.32 [+ or -] 0.01 0.30 [+ or -] 0.01 0.26 [+ or -] 0.02
T4 1.18 [+ or -] 0.01 1.08 [+ or -] 0.01 1.48 [+ or -] 0.01

Ralun
C 0.24 [+ or -] 0.01 0.24 [+ or -] 0.02 0.25 [+ or -] 0.01
T1 0.19 [+ or -] 0.01 0.20 [+ or -] 0.01 0.53 [+ or -] 0.02
T2 0.42 [+ or -] 0.01 0.43 [+ or -] 0.01 0.73 [+ or -] 0.01
T3 0.43 [+ or -] 0.01 0.49 [+ or -] 0.01 0.88 [+ or -] 0.01
T4 1.84 [+ or -] 0.01 1.94 [+ or -] 0.01 2.01 [+ or -] 0.02

Diguillin
C 0.24 [+ or -] 0.02 0.22 [+ or -] 0.01 0.26 [+ or -] 0.01
T1 0.20 [+ or -] 0.01 0.20 [+ or -] 0.00 0.25 [+ or -] 0.01
T2 0.33 [+ or -] 0.01 0.35 [+ or -] 0.01 0.46 [+ or -] 0.01
T3 0.59 [+ or -] 0.01 0.71 [+ or -] 0.02 0.80 [+ or -] 0.00
T4 1.90 [+ or -] 0.01 1.94 [+ or -] 0.01 2.24 [+ or -] 0.01

 Exchangeable cations (cmol/kg)

Sample 0 2 4

Collipulli
C 7.8 [+ or -] 0.0 7.8 [+ or -] 0.0 7.8 [+ or -] 0.0
T1 12.5 [+ or -] 0.0 13.0 [+ or -] 0.1 18.0 [+ or -] 0.2
T2 12.0 [+ or -] 0.1 13.0 [+ or -] 0.3 14.0 [+ or -] 0.2
T3 18.0 [+ or -] 0.1 18.0 [+ or -] 0.3 18.0 [+ or -] 0.2
T4 25.0 [+ or -] 0.1 26.0 [+ or -] 0.2 28.0 [+ or -] 0.3

Ralun
C 3.0 [+ or -] 0.0 3.0 [+ or -] 0.1 3.0 [+ or -] 0.1
T1 4.1 [+ or -] 0.1 4.0 [+ or -] 0.2 11.0 [+ or -] 0.2
T2 3.7 [+ or -] 0.1 4.0 [+ or -] 0.1 12.0 [+ or -] 0.1
T3 8.5 [+ or -] 0.2 9.0 [+ or -] 0.2 15.0 [+ or -] 0.4
T4 35.0 [+ or -] 0.1 37.0 [+ or -] 0.1 40.0 [+ or -] 0.2

Diguillin
C 10.0 [+ or -] 0.2 10.3 [+ or -] 0.2 10.3 [+ or -] 0.1
T1 11.1 [+ or -] 0.0 12.0 [+ or -] 0.1 17.0 [+ or -] 0.2
T2 10.0 [+ or -] 0.3 11.0 [+ or -] 0.3 19.0 [+ or -] 0.3
T3 15.3 [+ or -] 0.0 17.0 [+ or -] 0.2 21.0 [+ or -] 0.1
T4 40.0 [+ or -] 0.1 41.0 [+ or -] 0.3 49.0 [+ or -] 0.5

Table 3. Olsen P in amended soil samples (0), and after 2 and 4 months
of incubation

 Olsen P (mg/kg)

Sample 0 2

Collipulli
C 3.34 [+ or -] 0.15 3.78 [+ or -] 0.13
T1 8.27 [+ or -] 0.14 4.73 [+ or -] 0.26
T2 15.25 [+ or -] 0.81 11.30 [+ or -] 0.03
T3 14.28 [+ or -] 0.78 11.00 [+ or -] 0.42
T4 32.40 [+ or -] 1.00 37.86 [+ or -] 0.77

Ralun
C 7.08 [+ or -] 0.07 6.95 [+ or -] 0.10
T1 11.93 [+ or -] 0.27 9.02 [+ or -] 0.20
T2 9.40 [+ or -] 0.78 4.42 [+ or -] 0.01
T3 18.62 [+ or -] 0.16 18.25 [+ or -] 0.01
T4 37.95 [+ or -] 0.67 40.06 [+ or -] 0.59

Diguillin
C 6.17 [+ or -] 0.18 5.78 [+ or -] 0.02
T1 7.60 [+ or -] 0.34 9.03 [+ or -] 0.13
T2 31.41 [+ or -] 0.54 11.66 [+ or -] 0.18
T3 11.78 [+ or -] 0.67 12.91 [+ or -] 0.48
T4 35.95 [+ or -] 0.97 34.68 [+ or -] 1.14

 Olsen P (mg/kg)

Sample 4

Collipulli
C 3.70 [+ or -] 0.03
T1 4.18 [+ or -] 0.23
T2 10.69 [+ or -] 0.47
T3 7.79 [+ or -] 0.42
T4 33.19 [+ or -] 0.25

Ralun
C 7.09 [+ or -] 0.43
T1 10.76 [+ or -] 0.07
T2 5.68 [+ or -] 0.06
T3 19.13 [+ or -] 0.17
T4 45.00 [+ or -] 0.54

Diguillin
C 5.58 [+ or -] 0.04
T1 7.26 [+ or -] 0.04
T2 9.80 [+ or -] 0.26
T3 13.87 [+ or -] 0.32
T4 34.34 [+ or -] 0.71
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Article Details
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Author:Antilen, Monica; Briceno, Margarita; Galindo, Gerardo; Escudey, Mauricio
Publication:Australian Journal of Soil Research
Article Type:Technical report
Geographic Code:3CHIL
Date:Aug 1, 2008
Words:6388
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