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The use of organic amendments improves the quality and increases the fertility of the soils due to their adsorption properties, stimulates nutrient cycling and can be used to reduce the availability of heavy metals. The main objective of the research was to evaluate the effect of biochar (BC) derived from pig manure on the availability of Pb in a contaminated and limed agricultural soil. A randomized experimental design was applied, the pig manure was dried at room temperature (23 °C) and pyrolyzed at 500 °C for 2 h. Doses of 5%, 10% and 20% of BC were applied to the Pb soils contaminated (165.7 mg/kg), that were arranged in 2 kg pots except for the control sample, and Lactuca sativa was subsequently grown cultivated to evaluate the Pb availability. The results indicated an improvement in soil quality at higher BC dose, increase of 0.34 pH units, decrease of Pb extracted by EDTA (27% to 62% of decrease), and non-significant Pb content in leachates (< 1 mg Pb/L) and no detection in plant roots (< 0.01 mg/kg), except for the control plant (0.7 mg Pb/kg) in the original soil. A logarithmic relational model between BC dose and Pb adsorbed in the soil was obtained (R² = 0.9938, p < 0.05) showing that the decrease of Pb availability in the soil increased for higher BC doses, which represents an eco-friendly remediation alternative. It is recommended to investigate the interaction relationships between the soil quality parameters and to establish functional models of bioaccumulation and extractable metal of the amended soil. [ABSTRACT FROM AUTHOR]

A field experiment was conducted during Kharif and Summer seasons for two consecutive years of 2016-17 and 2017-18 with rice (Oryza sativa L.) and cowpea (Vigna unguiculata L.), grown in a sequence at Zonal Agricultural Research Station, Mandya on an acid soil to study the effect of biochar, lime and mangala setright on yield, nutrient uptake and fertility status of an acidic soil. Application of biochar along with soil test value based fertilizer (STV) + FYM + ZnSO4 influenced the productivity of rice and cowpea of 104.82 q ha−1 and 2474.77 kg ha−1, respectively and the uptake of nitrogen, phosphorus and potassium by rice (107.72, 28.16 and 69.34 kg ha−1, respectively) and cowpea (68.06, 5.86 and 38.67 kg ha−1, respectively) significantly, which was found on par with application of biochar along with RDF + FYM + ZnSO4. The soil pH (6.01), organic carbon content (5.03 g kg−1) and available nitrogen (340.45 kg ha−1), phosphorus (39.45 kg ha−1) and potassium (166.45 kg ha−1) significantly increased through the integrated use of biochar, FYM, ZnSO4 and fertilizers. Yield and soil properties like soil pH, organic carbon content and available nitrogen, phosphorus and potassium significantly increased with application of lime and mangala setright as compared to farmer's practice. Highest net income and benefit:cost ratio (2.65) was obtained with integration of soil test value based fertilizer application, FYM and biochar. Significant reduction in the productivity of crop and soil fertility was recorded in farmer's practice. [ABSTRACT FROM AUTHOR]