Sustainable soil and organic matter managements for reducing straw burning, greenhouse gas production and emission, and their influencing factors in Northwest India

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ABSTRACT Rice-wheat cropping system in Northwest India has been established since green revolution starting in the 1960s, based on modern varieties of crops and sufficient supply of water and nutrients. However, due to decrease in water availability and intensive cropping, soil fertility and soil organic matter contents started to decline. Also, mismanagement (burning) of crop residue induces air pollution, affecting human health. To address the issue of burning straw, other sustainable straw management alternatives are being evaluated from agronomic viewpoint. As for mitigation of air pollution and greenhouse gas emissions from soil, crop residue can be converted to biochar for various applications. We conducted field and laboratory incubation experiments to investigate the effects of two kinds of biochar (made from rice husk and rice straw) on soil properties and greenhouse gas emissions from wheat fields. After two seasons of field experiments, soil total C were increased only by rice-husk biochar application as compared with no amendment, rice straw biochar and chemical fertilizers. Greenhouse gases (GHGs; CO2, CH4 and N2O) were sampled by chamber method, measured by gas chromatography, then calculated emissions as CO2eq using Global Warming Potentials (GWPs). We found CO2 emission as dominant among three gases in the field experiment, although this included root respiration, and were not significantly changed by biochar application, compared to the control (chemical fertilizer application only). The incubation experiment showed that N2O was dominant among the three gases and increased by biochar application as compared to the control, corresponding to 0.9 and 14% of GHGs increase by rice-husk and rice-straw biochar, respectively, while the latter was equivalent to 0.2% of total C from rice-straw biochar applied. Although wheat yield was not significantly increased, the co-benefit of reduction in crop residue burning by rice-husk biochar application and contribution to international efforts of GHG emission mitigation envisage for sustainable carbon neutrality in an agriculture system.