Effect of biochar, lime, and compost application on

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However, there is limited information about the effect of biochar on P ... bark (HTC) and low temperature coal synthesized from sewage sludge (LTC) on the ...
J. Plant Nutr. Soil Sci. 2015, 000, 1–6

DOI: 10.1002/jpln.201400552

1

Effect of biochar, lime, and compost application on phosphorus adsorption in a Ferralsol Muhammad Farooq Qayyum1,2*, Imran Ashraf1, Muhammad Abid2, and Diedrich Steffens1 1

Institute of Plant Nutrition, Research Center for BioSystems, Land Use and Nutrition, Justus Liebig University, Heinrich-Buff-Ring 26–32, 35392 Gießen, Germany 2 Department of Soil Science, Faculty of Agricultural Sciences and Technology, Bahauddin Zakariya University, Multan, Pakistan

Abstract Use of biochar has multiple benefits like C, soil organic matter stabilization, and agricultural productivity. However, there is limited information about the effect of biochar on P dynamics in acidic soils. Hence, we investigated the effects of fresh and aged hydrothermal coal produced from bark (HTC) and low temperature coal synthesized from sewage sludge (LTC) on the kinetics of P adsorption in a Ferralsol. The treatments comprised of a control, compost [7.7 g (kg soil)–1], hydrothermal carbonization coal [HTC, 2 g (kg soil)–1], low temperature conversion coal [LTC, 3.8 g (kg soil)–1], lime [0.3 g CaO (kg soil)–1], compost + HTC [3.8 + 1.0 g (kg soil)–1], compost + LTC [3.8 + 1.9 g (kg soil)–1, respectively], compost + lime [7.6 and 0.4 g (kg soil)–1, respectively]. The soil samples were incubated for a period of 3 months at 60% of the maximum water holding capacity. After 5 d and 3 months of the incubation period soil pH, Ca-acetate lactate (CAL) extractable soil-P, and P-adsorption isotherms were determined. The results show a significant effect of treatments on soil pH just after 5 d, which remained consistent after three months of incubation. All treatments, except HTC increased the soil pH compared with the control treatment. The maximum increase in soil pH was observed with compost + lime (from 4.5 to 6.1). The CALextractable P was significantly increased with application of LTC, compost + LTC, and compost + lime. The sorption parameters were not affected after 5 d of incubation. Due to residence effects, the P sorption capacity (Sm) was significantly reduced in the LTC treatment [from 1182 to 1099 mg (kg soil)–1], and in the combination treatments compost + HTC [from 1182 to1078 mg (kg soil)–1], and compost + LTC [from 1182 to 1099 mg (kg soil)–1] treatments. The P binding energy (K) was significantly increased by the addition of LTC (from 2.18 to 4.26 mg L–1), lime (from 2.18 to 4.53 mg L–1), compost + HTC (from 2.18 to 7.03 mg L–1) and compost + LTC (from 2.18 to 4.68 mg L–1). Based on the results of the present study it is concluded that alone application of biochars do not alter the P bioavailability and sorption in a Ferralsol. However, combined application of biochars along with compost significantly decreases P sorption and increases bioavailability. Key words: hydrothermal carbonization coal / low temperature conversion coal / phosphorus sorption / compost / lime.

Accepted March 21, 2015

1 Introduction For sustainable agricultural productivity, efficient use and management of P are indispensable. To meet the crop’s need, huge amounts of inorganic P fertilizers are added to soils, which are manufactured using non-renewable mined rockphosphate (Cordell et al., 2009; 2011). Despite of high applications, the bioavailability of P is limited in highly weathered soils due to strong sorption with oxides and hydroxides of Fe and Al. In such soils, use of lime as an amendment may increase the bioavailability of P (Opala, 2011). As an alternate approach, organic amendments such as composts improve P bioavailability in P-fixing soils (Singh and Jones, 1976; Iyamuremye and Dick, 1996; Chen et al., 2001). Through mineralization of organic inputs in soils, inorganic P,

various organic acids (carboxylic acids, low molecular weight aliphatic acids), and dissolved organic substances are released (Guppy et al., 2005a, b; Johnson and Loeppert, 2006). These dissolved organic acids are sources of negative charges which compete with P for soil sorption sites (Nziguheba et al., 1998). Overall, with a decrease in reactive surfaces of Al and Fe, P concentration in soil solution is increased. Recently, the addition of biochar as an organic amendment in agriculture has received considerable interest. The idea of biochar originated from thousand-year old organic-rich soils of Terra Preta. In these soils, the pre-historic people had been using slash and burn activities to increase the soil fertility (Glaser et al., 2002). Burning of crop residues on field is still common practice in some regions of the world, but it is not

* Correspondence: Dr. M. F. Qayyum; e-mail: [email protected]

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J. Plant Nutr. Soil Sci. 2015, 000, 1–6

recommended due to negative effects on soil physical properties, nutrients transformations, and soil microbial abundance (Dooley and Treseder, 2012). Biochar production from waste agricultural residues under controlled conditions of pyrolysis and subsequent addition in soil is one of the safest ways of utilization. Almost all kinds of organic residues such as agricultural wastes, fruit and market wastes, and even sewage sludge can be used as feedstock. Recently many studies have shown beneficial effects of biochar in improving soil physicochemical properties and crop production. Major et al. (2010) applied biochar to a savanna Oxisol in Colombia and investigated its effects on maize yield and nutrition. Their data showed a significant increase in maize yield and a decrease in exchangeable Fe and Al when biochar was applied at rates of 8 and 20 t ha–1. Similarly, Chan et al. (2008) found a significant increase in extractable P on an Alfisol amended with green waste biochar at rates exceeding 50 t ha–1 in a greenhouse pot trial. It was suggested that this increase in extractable P (Colwell-P) might be due to C–P complexes formed in the biochars at various temperatures. Most of the biochars contain high amounts of condensed aromatic C compounds (Lehmann et al., 2007) and have a high specific surface area (Qayyum et al., 2012) and high charge densities (Yao et al., 2012). These properties allow biochars to sorb higher amounts of cations per unit mass than biogenic soil organic matter (SOM) (Liang et al., 2008; Sombroek et al., 2003). It has been suggested that increases in crop yield with biochar application might be due to an increase in soil pH in acidic soils, increased nutrient availabilities, and a decrease in phytotoxic Al (Kookana et al., 2011). Due to the alkaline properties biochars have a liming effect and reduce exchangeable acidity and exchangeable Al (Chintala et al., 2014a; Yuan and Xu, 2011), subsequently altering P sorption capacities. However, so far limited studies have been conducted on the effect of biochar on the release and bioavailability of P in highly weathered soils. The objective of our study was to investigate the effect of two biochars (different in their feed-

stock and production methodology) in combination with lime and compost on P adsorption in a highly weathered soil. Prior to the experiment, liming effects of biochars and compost were determined. Therefore, an equivalent amount of lime was used as an extra treatment to observe differences. It was hypothesized that biochar application on a Ferralsol will result in reduced P adsorption by binding Al and Fe and decreasing sorption sites.

2 Material and methods 2.1 Soil and the treatments A relic tertiary Ferralsol was used for the incubation experiment. This soil was a mixture of various soil horizons from an area near Gießen, Germany. The selected soil had high concentrations of oxalate (amorphous) and dithionite (crystalline) soluble Fe and Al, a low concentration of CAL-extractable soil-P and a high P-adsorption capacity. Briefly, the selected physicochemical properties are: texture, clay loam; pH, 5.50; CAL-P, 0.32 mg (kg soil)–1; DTPA-Fe, 12.2 mg (kg soil)–1; oxalate-Fe, 2,200 mg (kg soil)–1; oxalate-Al, 900 mg (kg soil)–1; dithionate-Al, 1,700 mg (kg soil)–1; and CEC, 3.20 cmolc (kg soil)–1. The physicochemical properties of the biochars and the compost are presented in Table 1. Two biochars, a hydrothermal carbonization coal from bark (HTC) and a low temperature conversion coal from sewage sludge (LTC) were selected in comparison to a compost and lime (CaO) treatment. Both kinds of biochars (HTC and LTC) are prepared at relatively low temperatures and their yield efficiency is higher as compared to traditional charcoal or fast pyrolysis methods (Libra et al., 2011; Weber et al., 2014). The effect of compost, when combined with biochar and lime, was also investigated. The amount of lime was applied after determination of the alkalinity in the biochars. The biochars were different from each other in feedstock material and method of production. A detailed description of the biochars used in the present experiment and the methodology regarding their physicochemical characterization is published elsewhere (Qayyum et al., 2012).

Table 1: Physicochemical properties of the hydrothermal carbonization coal (HTC), low temperature conversion coal (LTC), and compost. HTC Ash content

/ mg g–1

Mobile matter

/ mg g–1

Brunauer–Emmett–Teller surface area / Total carbon / mg g–1 Total nitrogen N

/ mg g–1

Total phosphorus Total sulfur and:

/ mg g–1

/ mg g–1

m2

g–1

LTC

Compost

28.40

19.70

71.35

19.60

2.70

28.65

9.75

7.14

510

265

nda 129.9

5.9

34.20

8.43

0.40

38.20

1.9

2.10

6.50

0.79

not determined.

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J. Plant Nutr. Soil Sci. 2015, 000, 1–6

Biochar and phosphorus adsorption 3

2.2 Incubation experiment As the percentage of C was different in the various biochars and compost, varying amounts of amendments were applied in order to provide 1 g C (kg soil)–1. The maximum alkalinity caused by any of the organic amendments was determined and equivalent amounts of lime were applied as further treatment. The C/N ratio of 10:1 was maintained in all treatments by adding NH4-nitrate. The treatments comprised of control (no amendment), compost [7.7 g (kg soil)–1], HTC [2.0 g (kg soil)–1], LTC [3.8 g (kg soil)–1], lime [0.3 g (kg soil)–1], compost + HTC [each 3.8 and 1.0 g (kg soil)–1, respectively], compost + LTC [each 3.8 and 1.9 g (kg soil)–1, respectively], and compost + lime [each 7.7 and 0.3 g (kg soil)–1, respectively]. For incubation, the weighed amounts of the treatments were mixed with 500 g of the soil and the mixtures were filled into plastic pots of 1 kg capacity. Moisture contents were maintained at 60% of water holding capacity of the soil throughout the incubation period by measuring weight loss at regular intervals. The soil samples in the pots were placed under dark inside a climate chamber at 26°C for 3 months. Each treatment was replicated for four times, and the whole experiment was repeated once to get samples after 5 d of incubation. Soil samples were taken 5 d and 3 months after incubation to determine the effect of treatments on soil pH, CAL-P, and P-adsorption isotherms.

2.3 Analyses Prior to the start of the experiment, the alkalinity of biochar and compost samples was determined according to a VDLUFA method (VDLUFA, 2008). Soil samples taken after 5 d and 3 months of incubation were oven-dried at 40°C, ground and passed through a 2-mm sieve. Soil pH was determined in a soil suspension with 0.01 M CaCl2 at a ratio of 1:2.5. Plant available P was measured with the CAL method (Schu¨ller, 1969). Briefly, 2.5 g soil sample was extracted with 50 mL Caacetate lactate solution after shaking for 2 h. The concentration of P in extracts was measured using a spectrophotometer.

Phosphorus adsorption isotherms were determined using the method of Bolan and Hedley (1990). Briefly, 1 g soil was weighed in polyethylene centrifuge bottles. Then 20 mL of 0.01 M CaCl2 containing several concentrations of P as KH2PO4 [0, 1.0, 2.5, 5.0, 10, 25, 50, and 100.0 mg P (kg soil)–1] were added to the soil in the bottles. The bottles were shaken continuously at 25°C for 24 h, and then filtered through a 0.45-mm membrane filter (CHROMAFIL Xtra PET–20/25, Macherey–Nagel Co., Germany). Phosphorus concentration in the filtrates was determined following the method of Murphy and Riley (1962). The sorption data were fitted to the Langmuir equation as follows: S¼

KL · Sm ·C ; 1 þ KL ·C

(1)

where C denotes the concentration of P remaining in the solution after 24 h equilibrium (mg P L–1), S the total amount of P sorbed (mg P kg–1), Sm is the sorption maximum (mg kg–1), and KL is a constant related to the binding energy (L kg–1).

3 Results 3.1 Effect of biochars, compost, and lime on soil pH and CAL-P Application of biochars, compost, lime, and the combination of amendments resulted in significant (P £ 0.05) variations in soil pH 5 d after incorporation (Table 2). However, after three months soil pH in all treatments remained the same as it was after 5 d. Except for HTC, all other treatments significantly increased pH over the control treatment. At both incubation times, the strongest effect on soil pH was found with compost + lime, in which the soil pH increased from 5.45 to 6.09. Overall, the treatments followed the trend in increasing soil pH: compost + lime > CaO > compost > compost + LTC > LTC > compost + HTC.

Table 2: Effect of control, compost, hydrothermal carbonization coal (HTC), low temperature conversion coal (LTC), lime (CaO), Compost + HTC, LTC + compost, and CaO + compost on soil pH and CAL-extractable soil-P after 5 d and 3 months of incubation in a Ferralsol. The values are mean – standard error. Different letters in parentheses along a column indicate significant differences between treatments at the 5% probability level (P £ 0.05). Treatments

CAL-P / mg P 100 g soil–1

pH (0.01 M CaCl2) 5 days

3 months

5 days

3 months

Control

5.45 – 0.01 (a)

5.47 – 0.01 (a)

0.47 – 0.03 (a)

0.38 – 0.01 (a)

Compost

5.68 – 0.02 (c)

5.68 – 0.01 (c)

0.55 – 0.02 (ab)

0.52 – 0.02 (ab)

HTC

5.42 – 0.01 (a)

5.44 – 0.00 (a)

0.45 – 0.03 (a)

0.50 – 0.02 (ab)

LTC

5.63 – 0.01 (bc)

5.65 – 0.01 (c)

1.38 – 0.03 (d)

1.27 – 0.10 (d)

Lime (CaO)

6.00 – 0.03 (d)

5.94 – 0.01 (d)

0.49 – 0.03 (ab)

0.50 – 0.02 (ab)

Compost + HTC

5.57 – 0.00 (b)

5.58 – 0.00 (b)

0.52 – 0.01 (ab)

0.54 – 0.01 (ab)

Compost + LTC

5.66 – 0.00 (c)

5.65 – 0.00 (c)

0.88 – 0.02 (c)

0.82 – 0.05 (c)

Compost + CaO

6.09 – 0.01 (e)

6.08 – 0.01 (e)

0.60 – 0.02 (b)

0.62 – 0.01 (b)

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J. Plant Nutr. Soil Sci. 2015, 000, 1–6

3.2 Sorption parameters It is evident that P adsorption increased with increasing P concentration in the solution (Fig. 1). After 5 d of incubation, the treatments did not statistically (P £ 0.05) affect the sorption capacity (Sm). However, after 3 months of incubation significant differences were observed between treatments (Table 3). Stronger conformity (r2) was observed for the 3 months incubated soil samples compared to 5 d. Sorption capacity (Sm) was significantly decreased with all combinations of treatments compared with the control. However, except for the control, other treatments were not statistically different from each other.

4 Discussion

1200 A Sorbed conc. / mg P kg–1 soil

The data indicate that the time of incubation had no influence on CAL-P. The addition of HTC, compost, CaO, and compost + HTC did not increase CAL-P significantly compared to the control treatment (Table 2). However, the treatments with compost, compost + LTC, and compost + lime significantly increased the CAL-P compared to the control. The maximum increase in CAL-P was observed with LTC [from 0.47 to 1.38 mg P (100 g soil)–1] followed by the compost + LTC [from 0.47 to 0.88 mg P (100 g soil)–1].

1000 Control Compost+HTC

800 600 400 200 0 0

2

4

6

8

10

12

–1

Equilibrium conc. / mg P L

1200 B Sorbed conc. / mg P kg–1 soil

4

1000

Control Compost+HTC

800 600 400

The increase in soil pH after application of lime and compost is a well-known mechanism, but our results show that LTC biochar was also effective in increasing soil pH (Table 2). Similarly, the combined application of compost and HTC also increased soil pH. Liu et al. (2012) also reported a significant effect of combined application of biochar and compost on pH and plant available nutrients in a Cambisol. Jones et al. (2012) also observed a significant effect of biochar on soil pH with the greatest effect observed in the second year after application.

Figure 1: Effect of control and compost + HTC on adsorption applied to the Langmuir equation after 5 days (A) and 3 months (B) of incubation in a highly weathered Ferralsol.

Results of our experiment show that the application of HTC, compost, and lime did not significantly influence the CAL-P and adsorption parameters. However, only the LTC and the

combinations of compost with LTC and CaO increased CAL extractable soil-P compared to the control treatment. Due to the application of 7.7 g compost (kg soil)–1,

200 0 0

2

4

6

8

10

12

–1

Equilibrium conc. / mg P L

Table 3: Effect of control, HTC (hydrothermal carbonization coal), LTC (low temperature conversion coal), compost, lime (CaO), compost + HTC, compost + LTC, and compost + lime on soil pH and CAL-extractable soil-P after 5 d and 3 months of incubation in a Ferralsol. Different letters along the columns indicates significant differences at the 5% probability level (P £ 0.05). K (Binding energy) / L kg–1

Sm / mg kg–1

5 days

3 months

5 days

3 months

5 days

3 months

Control

3.32

2.18

1133

1182 b

0.995

0.979

Compost

2.94

3.20

1145

1105 ab

0.993

0.999

HTC

3.24

3.16

1118

1114 ab

0.995

0.999

LTC

3.74

4.26

1119

1099 a

0.996

0.999

Lime (CaO)

3.37

4.53

1143

1107 ab

0.995

0.999

Compost + HTC

3.43

7.03

1124

1078 a

0.996

0.999

Compost + LTC

3.08

4.68

1130

1099 a

0.996

0.999

Compost + lime

3.05

3.43

1137

1121 ab

0.996

1.000

Treatments

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r2

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J. Plant Nutr. Soil Sci. 2015, 000, 1–6 1.46 mg P (100 g soil)–1 was applied and this resulted in an increase of CAL extractable soil-P. However, with the addition of 3.8 g LTC (kg soil)–1, 14.5 mg P (100 g soil)–1 were added. The relatively high P concentration in the LTC was caused by the carbonization of sewage sludge, which has a high P content. There are some reports noting the high concentration of P in sewage sludge biochars (Bridle and Pritchard, 2004; Hossain et al., 2010). It is due to fact that P compounds are not volatilized during pyrolysis (temperatures < 550°C), and with reduction in mass, the total P content in the resulting biochar is increased (Bridle and Pritchard, 2004). In this context it is surprising that only 10% of the applied LTC-P was extractable with the CAL method either after 5 d or 3 months of incubation although the soil pH was 5.4. This result shows that P might have been converted to a relatively unavailable P compound, which is not CAL-extractable. We assume that sewage sludge P is converted to an apatitic structure due to the carbonization at 400°C. The HTC biochar that was produced from tree bark did not contain high amounts of P and could not increase CAL-P significantly. Similar to our findings, Sinclair et al. (2010) did not observe a significant increase in plant available P following amendment with green waste biochar. In this case our HTC biochar may be regarded as similar to that of green waste biochar. Similar to our results, Yao et al. (2012) could not find biochar as an effective sorbent for phosphate. In contrast, Chintala et al. (2013) reported significant reduction in P-sorption to an Oxisol after application of corn stover and switch grass biochars. Higher amounts of Al and Fe present in the Ferralsol can strongly fix P and make it unavailable to plants. Strong fixation of P in soil is obvious from the highest Sm value of the control treatment (1,182 mg kg–1). The high adsorption in the control soil may be due to high values of dithionate extractable Fe and Al (Westermann, 1992). Only the compost application and the combination of compost with HTC and LTC significantly decreased Sm values indicating a strong reduction in P sorption. This indicates that probably organic anions from the compost have sorbed on negatively charged surfaces in the soil (Guppy et al., 2005a, b).

Biochar and phosphorus adsorption 5

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