Impact of rice-straw biochar on some selected soil properties and rice (Oryza sativa L.) grain yield

Abstract Biochar is a co-product of pyrolysis of rice straw biomass, its qualities vary according to pyrolysis conditions but it mainly contains phosphorus and potassium. The carbon (C) content in biochar is stable, so it can be applied to soils which enlarging the C sink. In the present investigation, a biochar was produced from rice straw residue, characterized and its effect on rice grain yield, pH, soil organic carbon, total N and changes in NH4+–N and NO3-–N concentrations in rice soil under intermittent wetting-drying and continuous flooding were examined. The results showed that, the rice straw-derived biochair produced was neutral in pH and the cation exchange capacity 37 cmol kg -1. Application of biochar, reduces the NH4+–N and NO3-–N concentrations in soil irrespective of moisture conditions. Such effect was more pronounced on NH4+–N and NO3-–N concentrations under flooding condition and intermittent wetting&drying condition, respectively. Increasing the rate of rice straw derived biochair application rate had significantly decreased both the NH4+–N and NO3-–N concentrations in soil. The resulted rice yield from T3 (30 g biochair per kg-1 dry soil) was the highest and significant difference compared to other treatments. The biochair application significantly enhanced the total soil N, soil organic carbon and soil pH under both flooding and wetting&drying conditions.