Mutual relationships of biochar and soil pH,CEC, and exchangeable base cations in a model laboratory experiment

Purpose

The majority of biochar studies use soils with only a narrow range of properties making generalizations about the effects of biochar on soils difficult. In this study, we aimed to identify soil properties that determine the performance of biochar produced at high temperature (700 °C) on soil pH, cation exchange capacity (CEC), and exchangeable base cation (Ca²⁺, K⁺, and Mg²⁺) content across a wide range of soil physicochemical properties.

Materials and methods

Ten distinct soils with varying physicochemical properties were incubated for 12 weeks with four rates of biochar application (0.5, 2, 4, and 8% w/w). Soil pH, CEC, and exchangeable base cations (Ca²⁺, K⁺, and Mg²⁺) were determined on the 7th and 84th day of incubation.

Results and discussion

Our results indicate that the highest biochar application rate (8%) was more effective at altering soil properties than lower biochar rates. Application of 8% biochar increased pH significantly in all incubated soils, with the increment ranging up to 1.17 pH unit. Biochar induced both an increment and a decline in soil CEC ranging up to 35.4 and 7.9%, respectively, at a biochar application rate of 8%. Similarly, biochar induced increments in exchangeable Ca²⁺ up to 38.6% and declines up to 11.4%, at an 8% biochar application rate. The increment in CEC and exchangeable Ca²⁺ content was found in soils with lower starting exchangeable Ca²⁺ contents than the biochar added, while decreases were observed in soils with higher exchangeable Ca²⁺ contents than the biochar. The original pH, CEC, exchangeable Ca²⁺, and texture of the soils represented the most crucial factors for determining the amount of change in soil pH, CEC, and exchangeable Ca²⁺ content.

Conclusions

Our findings clearly demonstrate that application of a uniform biochar to a range of soils under equivalent environmental conditions induced two contradicting effects on soil properties including soil CEC and exchangeable Ca²⁺ content. Therefore, knowledge of both biochar and soil properties will substantially improve prediction of biochar application efficiency to improve soil properties. Among important soil properties, soil exchangeable Ca²⁺ content is the primary factor controlling the direction of biochar-induced change in soil CEC and exchangeable Ca²⁺ content. Generally, biochar can induce changes in soil pH, CEC, and exchangeable Ca²⁺, K⁺, and Mg²⁺ with the effectiveness and magnitude of change closely related to the soil’s original properties.

     

Method for determining the acid ameliorating capacity of plant residue compost,urban waste compost,farmyard manure,and peat applied to tropical soils

Abstract

Plant residue compost, urban waste compost, farmyard manure, and peat can be used to ameliorate soil acidity. The diversity of these materials and their highly variable composition mean that their reliability in increasing the soil pH is uncertain because of lack of a method to test their acid ameliorating capacities. Incubation of a Spodosol from Sumatra, an Oxisol from Burundi and an Ultisol from Cameroon with 1.5% by weight of four composts, a farmyard manure and a sedge peat resulted in increased soil pH and decreased aluminum (Al) saturation measured at 14 days of incubation. The increased soil pH was directly proportional to the protons consumption capacity of the organic materials. This was measured by titrating the organic material from their natural pH values down to pH 4.0. This measure of acid neutralizing capacity provides a simple test method that was reliable across the variety of materials used. The final pH of the soil treated with organic material can be predicted with reasonable accuracy by determining the buffer characteristics of the soil and organic matter separately. The pH at the intersection of the two buffer curves predicts reasonably accurately the final pH of the treated soil. This suggests that a major mechanism of acid amelioration may be proton exchange between the soil and organic matter buffer systems. The increased soil pH was also directly proportional to the base cations [calcium (Ca), magnesium (Mg), and potassium (K)] contents of the added organic material. Such a relationship was presumably obtained because the base cations reflected the content of weak organic acid functional groups that are capable of binding protons and Al.     

Effects of biochar compared to organic and inorganic fertilizers on soil quality and plant growth in a greenhouse experiment

Our contemporary society is struggling with soil degradation due to overuse and climate change. Pre‐Columbian people left behind sustainably fertile soils rich in organic matter and nutrients well known as terra preta (de Indio) by adding charred residues (biochar) together with organic and inorganic wastes such as excrements and household garbage being a model for sustainable agriculture today. This is the reason why new studies on biochar effects on ecosystem services rapidly emerge. Beneficial effects of biochar amendment on plant growth, soil nutrient content, and C storage were repeatedly observed although a number of negative effects were reported, too. In addition, there is no consensus on benefits of biochar when combined with fertilizers. Therefore, the objective of this study was to test whether biochar effects on soil quality and plant growth could be improved by addition of mineral and organic fertilizers. For this purpose, two growth periods of oat (Avena sativa L.) were studied under tropical conditions (26°C and 2600 mm annual rainfall) on an infertile sandy soil in the greenhouse in fivefold replication. Treatments comprised control (only water), mineral fertilizer (111.5 kg N ha^–1, 111.5 kg P ha^–1, and 82.9 kg K ha^–1), compost (5% by weight), biochar (5% by weight), and combinations of biochar (5% by weight) plus mineral fertilizer (111.5 kg N ha^–1, 111.5 kg P ha^–1, and 82.9 kg K ha^–1), and biochar (2.5% by weight) plus compost (2.5% by weight). Pure compost application showed highest yield during the two growth periods, followed by the biochar + compost mixture. biochar addition to mineral fertilizer significantly increased plant growth compared to mineral fertilizer alone. During the second growth period, plant yields were significantly smaller compared to the first growth period. biochar and compost additions significantly increased total organic C content during the two growth periods. Cation‐exchange capacity (CEC) could not be increased upon biochar addition while base saturation (BS) was significantly increased due to ash addition with biochar. On the other hand, compost addition significantly increased CEC. Biochar addition significantly increased soil pH but pH value was generally lower during the second growth period probably due to leaching of base cations. Biochar addition did not reduce ammonium, nitrate, and phosphate leaching during the experiment but it reduced nitrification. The overall plant growth and soil fertility decreased in the order compost > biochar + compost > mineral fertilizer + biochar > mineral fertilizer > control. Further experiments should optimize biochar–organic fertilizer systems.     

Biochar‐compost substrates in short‐rotation coppice: Effects on soil and trees in a three‐year field experiment

Both biochar and compost may improve carbon sequestration and soil fertility; hence, it has been recommended to use a mixture of both for sustainable land management. Here, we evaluated the effects of biochar–compost substrates on soil properties and plant growth in short rotation coppice plantations (SRC). For this purpose, we planted the tree species poplar, willow, and alder in a no‐till field experiment, each of them amended in triplicate with 0 (= control) or 30 Mg ha^?1 compost or biochar–compost substrates containing 15% vol. (TPS15) and 30% vol. biochar (TPS30). For three years running, we analyzed plant growth as well as soil pH, potential cation exchange capacity (CEC), stocks of soil organic carbon (SOC), total N, and plant‐available phosphate and potassium oxide.Biochar‐compost substrates affected most soil properties only in the topsoil and for a limited period of time. The CEC and total stocks of SOC were consistently elevated relative to the control. After three years the C gain of up to 6.4 Mg SOC ha^?1 in the TPS30 plots was lower than the added C amount. Especially in the case of TPS30 treatment, C input was characterized by the greatest losses after application, although the black carbon of the biochar was not degraded in soil. Additionally, tree growth and woody biomass yield did not respond at all to the treatments. Overall, there were few if any indications that biochar–compost substrates improve the performance of SRC under temperate soil and climate conditions. Therefore, the use of biochar for such systems is not recommended.     

Chemistry of Cr in some Swedish soils. 6. Native P transformation and changes in pH and cation exchange capacity in two soils incubated with potassium chromate

Abstract

Transformation of native P and changes in water pH and cation exchange capacity (CEC‐pH 7) were investigated in acid (I) and neutral (IV) soil incubated with 0, 50 and 100 mg Cr/kg for 3 months. Phosphorus was sequentially obtained as P‐resin, P‐NaHCO₃, P‐NaOH and P‐HCl, with the P‐NaHCO₃ and P‐NaOH being separated into organic and inorganic fractions. The low Cr level had little impact on the parameters. The high level increased the pH from 5.1 to 7.3 and from 6.8 to 7.5 in soils I and IV, respectively, while also significantly (P=5%) increasing CEC and decreasing P‐resin content. Subsequent to the Cr treatment, total P‐NaHCO₃ significantly declined in Soil I, but did not change markedly in Soil IV. Although total P‐NaOH was not affected by the Cr applications, its inorganic form doubled in Soil IV. Most of the total P‐NaHCO₃ and P‐NaOH was in organic form. Whereas P‐HCl was stable in Soil IV, the P nearly doubled in Soil I at the expense of P‐NaHCO₃ (r = ‐0.94**). pH was correlated with CEC (0.62*), total P‐NaHCO₃ (‐0.83**) and P‐HCl (0.76**), while CEC was correlated with P‐resin (‐0.70**), total NaHCO₃ (‐0.88**) and P‐HCl (0.94**).     

Redistribution and Availability of Iron,Manganese, Zinc,and Copper in Four Malian Agricultural Soils Amended with Solid Municipal Waste Compost

Abstract

Municipal waste compost can improve the fertility status of tropical soils. The redistribution of iron (Fe), manganese (Mn), zinc (Zn), and copper (Cu) in tropical soils after amendment with solid municipal waste compost was investigated. Four tropical agricultural soils from Mali characterized by poor trace‐element status were amended with compost and incubated for 32 weeks at 35°C. The soil were analyzed at the beginning and the end of the incubation experiment for readily available fractions, organic fractions, and residual fractions as operationally defined by sequential extraction. Readily available Fe increased significantly with compost application in most soils. Readily available Mn was mostly unaffected by compost application. After 32 weeks, readily available Zn had increased, and readily available Cu had decreased. Readily available levels of the elements remained greater than deficiency levels in the compost‐amended soils. Organic fractions of the elements increased after compost addition. The organic fractions and residual forms, depending on the element and the soil, remained constant or increased within the duration of the experiment.     

Carbon content in soil particle size and consequence on cation exchange capacity of Alfisols

Abstract

Many of the cultivated soils of sub‐Saharan Africa typically have a surface horizon low in clay and with a low cation exchange capacity (CEC). In these soils, CEC is largely due to the soil organic matter (SOM). Measurements made on long‐term trials show that changes in CEC and SOM are positively correlated to one another, but not of same magnitude, suggesting that not all of the SOM plays an equal role as regards the soil CEC. To study the influence of the different SOM size fractions on the CEC, soils with or without application of manure or compost coming from trials in Chad and Côte d'Ivoire were separated without destruction of the SOM into five organo‐mineral fractions: “coarse sand”;, “fine sand”;, “coarse silt”;, “fine silt”;, and “clay”; made up of particles of sizes between 2,000 and 200, 200 and 50, 50 and 20, 20 and 2, and 2 and 0 μm, respectively. Fractionation was carried out by mechanical dispersion of the soil, wet sieving of the fractions larger than 20 μm, and decanting of the “clay”; and “fine silt”; fractions. The CEC of these fractions increases inversely with their size. The “clay”; fraction which contains half of the SOM contributes about 80% of the CEC of the soils. The CEC of the fractions is largely a function of their carbon (C) content, but the organic CEC per unit C of the “clay”; fraction appears to be four times greater than that of the other fractions (1,000 as against 270 cmol_c kg^‐1). Applications of manure or compost increase the CEC of the soils by increasing the soil C only when this C increase concerns the fine fractions of the SOM.     

有机物料与化肥配施提高黄泥田水稻产量和土壤肥力

农业有机物料具有资源化再利用的特点,与化肥配施既可以保证作物产量,也可以提升地力。为了建立最适宜的南方低产黄泥田培肥模式,该文在浙江金衢盆地开展3年田间试验研究化肥与不同有机物料(菇渣、紫云英、牛粪和秸秆)配施对水稻产量和土壤肥力的影响。结果表明:1)有机物料与化肥配施可以显著提高水稻产量,化肥+菇渣、化肥+紫云英、化肥+牛粪和化肥+秸秆处理下,水稻三年的平均产量分别比单施化肥提高了9.7%、9.5%、12.3%和9.5%;2)有机物料与化肥配合施用,土壤有机质、土壤养分(全氮、有效磷、速效钾和CEC)及土壤容重较单施化肥处理有一定程度的改善,其中,化肥+牛粪效果最明显,有机质质量分数提高了12.5%,土壤有效磷质量分数提高了37.7%,CEC提高了16.1%;3)与单施化肥相比,化肥+菇渣、化肥+牛粪处理下5 mm机械稳定性大团聚体分别提高了10.4%和6.7%,各配施处理均显著降低了团聚体破坏率。总得来讲,连续三年有机物料与化肥配施较单施化肥处理提高了水稻产量、改善了土壤肥力状况、增加了土壤团聚体稳定性,其中又以牛粪与化肥配合施用效果最佳。     

Contribution of organic matter and clay minerals to the cation exchange capacity of soils

Abstract

The cation exchange capacity (CEC) at pH 7 was measured for samples of 347 A horizons and 696 B horizons of New Zealand soils. The mean CEC was 22.1 cmolc/kg for the A horizons and 15.2 cmolc/kg for the B horizons. Multiple regressions were carried out for CEC against organic carbon (C), clay content, and the content of seven groups of clay minerals. The results, significant at p <0.001, were consistent with most of the CEC arising from soil organic matter. For the samples of A horizon, the calculated CEC was 221 cmolc/kg per unit C and for the B horizons was 330 cmolc/kg C. There was also a contribution from sites on clay minerals. Multiple regression indicated that smectite had a higher CEC (70 cmolc/kg) than other minerals but it was not as high as that of type smectites; kaolin minerals had the lowest CEC. There was a significant effect of interaction between organic matter and some clay minerals on the CEC. Samples from B horizons containing allophane had lower CEC than those not containing allophane which is consistent with allophane reacting with carboxyl groups on organic matter. For the samples from the A horizons, however the CEC was higher when allophane was present.     

Sustainability of organic fertilization of macadamia with macadamia husk‐manure compost

Abstract

Macadamia husk‐manure compost was evaluated as an organic fertilizer for the production of macadamia in an experiment over four years at irrigated and unirrigated sites on the MacFarms of Hawaii orchard. The treatments were (1) Fertilizer, a combination of solid and liquid chemical fertilizers applied based on leaf and soil analysis, (2) Compost, 10,000 kg ha^‐1 of a macadamia husk‐cattle manure compost alone applied annually between July and October, and (3) Compost+, compost plus mineral fertilizers applied based on leaf and soil analysis. In‐shell nut and kernel yield and quality were higher at irrigated than unirrigated sites, but were not significantly affected by the treatments. Change in leaf nutrient composition appears minimum except for slightly lower nitrogen (N) and boron (B) at two orchard sites for the compost treatment. Compost increased soil pH, total ion exchange capacity, soil organic matter, potassium (K), calcium (Ca), magnesium (Mg) at all sites, and sodium (Na) at irrigated sites. Soil nitrate (NO)‐N was lower in the compost treatment. Fertilization with compost was not profitable because the cost of compost application exceeded conventional fertilization cost tenfold for MacFarms, the largest macadamia farm in the United States.     

Municipal Solid Waste Compost Improves Crop Productivity in Saline-Sodic Soil: A Multivariate Analysis of Soil Chemical Properties and Yield Response

A pot experiment was conducted in sandy clay loam saline-sodic soil to assess the effects of farm yard manure (FYM), municipal solid waste (MSW) composts and gypsum application on nitrate leaching, soil chemical properties and crop productivity under rice-wheat cropping system. It also aims at establishing the correlation between soil phsico-chemical properties and yield response using principle component analysis and Pearson correlation analysis. The MSW was decomposed aerobically, an-aerobically and co-composted. Maximum nitrate leaching was observed during rice (75.9 mg L^?1) and wheat (37.2 mg L^?1) with an-aerobically decomposed MSW as compared with control treatment. Results revealed a decrease in soil pH (?6.95% and ?8.77%), electrical conductivity (EC) (?48.13% and ?51.04%), calcium carbonate (CaCO₃) (?40.30% and ?48.96%), and sodium adsorption ratio (SAR) (?40.27% and ?45.98%) with an-aerobically decomposed MSW compost during rice and wheat, respectively. In this treatment, organic matter (OM) (93.55% and 121.51%) and cation exchange capacity (CEC) (19.31% and 31.79%) were the highest as compared with control treatment during rice and wheat, respectively. Rice and wheat growth were significantly (p≤ 0.05) increased by an-aerobically decomposed MSW followed by co-compost, aerobically decomposed MSW, FYM, gypsum and control. Furthermore, Pearson correlation coefficients predicted significant positive correlation of yield with soil OM, and CEC while inverse relationship was observed with EC, pH, CaCO₃, and nitrogen use efficiency. Soil amelioration with organic and gypsum amendments was further confirmed with principal component analysis. This study has proved an-aerobically decomposed MSW as an effective solution for MSW disposal, thereby improving soil chemical properties and crop productivity from sandy clay loam saline-sodic soil.     

Bioassays and application of olive pomace compost on emmer: effects on yield and soil properties in organic farming

Abstract

Composting olive oil pomace could solve the problem of disposal, by recycling this organic waste for agricultural purposes. Furthermore, application of composted organic waste could be a way to sustain both soil fertility and production, especially in organic farming. Therefore, the aim of this research was to evaluate the phytotoxicity and the effects of application of olive pomace composts on emmer performance and soil properties. Two types of olive pomace composts, with a different initial C/N ratio, were stopped at the active phase and processed until maturation. The obtained four olive pomace composts were compared with a commercial fertilizer in a two-year field experiment. Before the field trial, a bioassay was performed to assess phytotoxicity both for the raw pomace and the not-stabilized composts. Growing and yielding data for emmer were determined during the two-year period and soil characteristics were measured at the start and at the end of the experiment.

The composts were not phytotoxic (germination index was higher than 90%) and their total organic carbon content was always higher than the minimum values established by the Italian fertilizers legislation. The emmer protein content was significantly higher in the matured compost treatment with low C/N, than in the other compost treatments. Its value was comparable with that of the commercial fertilizer, suggesting a good performance on crop yield quality. Although not significant, this compost showed an increase of 9.8% in grain yield compared with commercial fertilizer treatment. On the whole, it can be suggested that repeated compost application might preserve the soil organic carbon content and supply macronutrients to a crop.     

Cation exchange capacity variations in acidic forest soils from Sutton,Québec,Canada

Abstract

Single values of the cation exchange capacity (CEC) are widely used in modeling soil solution chemistry in soil and water ecosystems. Our aim was to determine the CEC as a function of pH and ionic strength in an acidic forest soil. We examined the cation exchange of two Humo‐Ferric Podzols (Haplorthods) equilibrated with artificial soil solutions of different concentrations. Aliquots of acid (HC1) or base (NaOH) were added to generate a pH range of 3 to 6. The CEC, determined by displacement with BaCl₂ showed little or no increase with increasing pH and a definite increase with lower pH. This anomalous behavior was attributed to the precipitation of aluminum (Al) at high pH and to its dissolution at low pH.     

Ammonia volatilization from urea-treated pasture and tillage soils: effects of soil properties

Mean NH₃ losses after nine days incubation at 18°C and 60% FC were 3.1±2.9% and 7.6±6.0% of applied urea-N from the pasture and tillage counterparts of 10 soil series. These losses were highly correlated with buffered CEC and maximal pH values (pH_m) generated three days after urea application. NH₃ volatilization was apparently controlled by buffered CEC and initial pH (R²= 72–87%) and was related to variations in soil organic matter and texture (R²= 77–81%). Losses in the acid pasture soils were attributed largely to initial pH differences, and in the tillage soils to buffered CEC only. Evolution was greater from the tillage than from the pasture equivalent in eight series. This was attributed to differences in CEC, including buffered CEC and pH-dependent charge, caused by differences in OM content primarily but also in texture between the two soil groups. Differences in NH₃ evolution from urea in pasture and tillage soils, in general, are not related to pH differences.     

Changes in Soil Properties and Vegetable Growth in Preparation for Organic Farming in Hawaii

Changes in soil properties and vegetable growth were quantified on a low-fertility tropical soil. Four treatments (two composts, urea, and control) were applied to an Oxisol (Rhodic Haplustox, Wahiawa series) in a field on Oahu, Hawaii. Chinese cabbage (Brassica rapa, Chinensis group) and eggplant (Solanum melongena) were grown sequentially as test crops. Soil quality as measured by hot-water-soluble carbon, dehydrogenase activity, and cation exchange capacity (CEC) increased by compost amendments. Total organic carbon or carbon dioxide (CO₂) respiration rate did not correlate with the soil amendments. Nitrogen (N) nutrition was the main factor that improved growth and carotenoid content in cabbage. The urea treatment promoted better growth in cabbage, whereas good-quality compost, made of grass clippings/tree trimmings, lime, and rock phosphate yielded better growth in eggplant, suggesting organic N requires time to mineralize and to be available to crops.     

Effects of drying on the ion exchange capacity and cation adsorption properties of some New Zealand soils

Abstract

The effect of drying on the cation (CEC) and anion (AEC) exchange capacity, and on potassium (K) and magnesium (Mg) adsorption by three New Zealand soils was investigated. Air‐drying resulted in no significant changes in these properties compared with the field‐moist samples. Oven‐drying at 105°C significantly decreased the CEC and increased the AEC of most soils compared with air‐dried samples. The decrease in CEC was related to increased solubility of organic matter and a decrease in surface area on which charge could be developed. The increase in AEC was attributed to a decrease in soil pH.

Potassium and Mg adsorption by two soils decreased following oven‐drying. This was consistent with the effect of drying on CEC. For the remaining soil, K adsorption increased following oven‐drying. This was attributed to K fixation.     

Additional application of aluminum sulfate with different fertilizers ameliorates saline-sodic soil of Songnen Plain in Northeast China

Purpose

Serious soil salinization, including excessive exchangeable sodium and high pH, significantly decreases land productivity. Reducing salinity and preventing alkalization in saline-sodic soils by comprehensive improvement practices are urgently required. The combinations of aluminum sulfate with different types of fertilizer at different rates were applied on rice paddy with saline-sodic soils of the Songnen Plain in Northeast China to improve soil quality and its future utilization.

Materials and methods

Experiments were carried out in a completely randomized block design. Twelve treatments with aluminum sulfate at the rates of 0, 250, 500, and 750 kg hm^?2 with inorganic, bio-organic, and organic-inorganic compound fertilizers were performed. Soil pH, electronic conductivity (EC), cation exchangeable capacity (CEC), exchangeable sodium percentage (ESP), total alkalinity, sodium adsorption ratio (SAR), soil organic carbon (SOC), available nutrients, soluble ions, rice growth, and yield in the saline-sodic soils were measured across all treatments. The relationships among the measured soil attributes were determined using one-way analysis of variance, correlation analysis, and systematic cluster analysis.

Results and discussion

The pH, EC, ESP, total alkalinity, SAR, Na⁺, CO₃^2?, and HCO₃^? in saline-sodic soil were significantly decreased, while CEC, SOC, available nitrogen (AN), available phosphorus (AP), available potassium (AK), K⁺, and SO₄^2? were significantly increased due to the combined application of aluminum sulfate with fertilizer compared with the fertilizer alone. The most effective treatment in reducing salinity and preventing alkalization was aluminum sulfate at a rate of 500 kg hm^?2 with organic-inorganic compound fertilizer. This treatment significantly decreased the soil pH, EC, ESP, total alkalinity, SAR, Na⁺, and HCO₃^? by 5.3%, 28.9%, 41.1%, 39.3%, 22.4%, 23.5%, and 35.9%, but increased CEC, SOC, AN, AP, AK, K⁺, SO₄^2?, rice height, seed setting rate, 1000-grain weight, and yield by 77.5%, 115.5%, 106.3%, 47.1%, 43.3%, 200%, 40%, 6.2%, 43.9%, 20.3%, and 42.2%, respectively, compared with CK treatment in the leaching layer.

Conclusions

The combined application by aluminum sulfate at a rate of 500 kg hm^?2 with organic-inorganic compound fertilizer is an effective amendment of saline-sodic soils in Songnen Plain, Northeast China. These results are likely related to the leaching of Na⁺ from the soil leaching layer to the salt accumulation layer and desalination in the surface soil, and the increase of SOC improved the colloidal properties and increased fertilizer retention in soil. In addition, the environmental impact of aluminum sulfate applied to soil needs to be further studied.

     

Evaluation of the maturity of municipal waste compost using simple chemical parameters

Abstract

Changes in different chemical parameters of the mixtures of several organic residues during composting were studied in order to establish simple parameters that can be useful as indices of compost maturity. Circular chromatography test and the study of the colour in solid samples of compost cannot be considered sufficiently reliable for determining the degree of maturity in composts. Similarly, parameters such as ash, C/N ratio, CEC, total organic carbon (TOC), and total nitrogen (TN) must be ruled out. Other parameters such as water soluble carbon (WSC), water soluble carbohydrates, the C/N ratio of the water soluble extract, and the ratios WSC/TN and CEC/TOC, can be used as indices of compost maturity.     

pH effects of the addition of three biochars to acidic Indonesian mineral soils

Abstract

Soil acidity may severely reduce crop production. Biochar (BC) may increase soil pH and cation exchange capacity (CEC) but reported effects differ substantially. In a systematic approach, using a standardized protocol on a uniquely large number set of 31 acidic soils, we quantified the effect of increasing amounts (0–30%; weight:weight) of three types of field-produced BCs (from cacao (Theobroma cacao. L.) shell, oil palm (Elaeis guineensis. Jacq.) shell and rice (Oryza sativa. L.) husk) on soil pH and CEC. Soils were sampled from croplands at Java, Sumatra and Kalimantan, Indonesia. All BCs caused a significant increase in mean soil pH with a stronger response and a greater maximum increase for the cacao shell BC addition, due to a greater acid neutralizing capacity (ANC) and larger amounts of extractable base cations. At 1% BC addition, corresponding to about 30 tons ha^?1, the estimated increase in soil pH from the initial mean pH of 4.7 was about 0.5 units for the cacao shell BC, whereas this was only 0.05 and 0.04 units for the oil palm shell and rice husk BC, respectively. Besides depending on BC type, the increase in soil pH upon the addition of each of the three BCs was mainly dependent on soil CEC (low CEC resulting in stronger pH increase), and to a lesser extent on initial soil pH (higher initial pH resulting in stronger pH increase). Addition of BC also increased the amount of exchangeable base cations (cacao shell ? oil palm and rice husk) and CEC. Through this systematic screening of the effect of BC on pH and CEC of acidic soils, we show that a small addition of BC, in particular if made of cacao shell, to acidic agricultural soils increases soil pH and CEC. However, the response is highly dependent on the type, quality and amount of the added BC as well as on intrinsic soil properties, mainly CEC.     

Comparison of paddy soil fertility under conventional rice straw application versus cow dung compost application in mixed crop–livestock systems in a cold temperate region of Japan

ABSTRACT

After the rice harvest in Japan, rice straw (RS) is usually cut by combine harvester and incorporated into the soil to improve its fertility. In mixed crop–livestock systems, however, RS is collected and used as livestock feed, and cow dung compost (CDC) is then applied to the soil. This system utilizes the residual organic matter from both rice production and livestock husbandry to make each product. CDC application is also considered to improve the fertility of paddy soil. However, the nutrient input from CDC and the effect of CDC application on soil fertility vary among regions and/or soil types. We compared soil fertility between RS application (RS treatment, avg. 32 years) and RS removal plus CDC application (CDC treatment, avg. 21 years) in 79 paddy fields in Mamurogawa town, Yamagata Prefecture, a cold temperate region of Japan, and measured the nutrient contents in the applied RS and CDC. The total C content of RS was significantly higher than that of CDC, whereas the N, P, K, and Si contents of CDC were significantly higher than those of RS. However, there was no significant difference in paddy soil fertility – as measured by soil organic C, total N, CEC, available N, P, and Si, exchangeable K, Ca, and Mg, base saturation percentage, pH, and bulk density – between the treatments. The soil fertility of most fields was adequate by RS or CDC treatment. Thus, leaving RS in paddy fields or removing it and then adding CDC to the paddy fields has a similar effect in maintaining adequate soil fertility for single rice production or rice–livestock production systems.