Organic amendments: Effect on carbon mineralization and crop productivity in acidic soil

Addition of organic amendment with inorganic fertilizers is a suitable strategy to achieve sustainable agricultural production. But this practice is associated with increased carbon mineralization leading to release of carbon dioxide, a potential greenhouse gas for global warming. In this perspective, the present experiment was conducted in acidic sandy loam soils of north-east India to characterize the carbon mineralization, soil enzyme activities and okra (Abelmoschus esculentus L.) productivity under three (farmyard manure, vermicompost and biochar) commonly used organic amendments when added with inorganic fertilizers. Eight treatments were laid in a randomized block design with three replications. Vermicompost application increased the activities of soil enzymes with greater availability of soil nitrogen, phosphorous and potassium while biochar (hardwood) addition decreased the enzyme activities. Addition of biochar recorded the lowest rate of carbon mineralization (9%), the highest half -life of carbon (64%), higher soil organic carbon (12%) and stable organic carbon fractions (F3 fraction-12% and F4 fraction- 9%) with the highest okra yield compared to vermicompost and farmyard manure. Plant morphological attributes (plant height, leaf number, leaf area and photosynthesis of okra) were significantly enhanced due to addition of organics especially vermicompost and biochar with inorganic fertilizers. The addition of biochar recorded lower benefit cost ratio (3.5 and 3.8) but its application with inorganic fertilizers recorded the highest agronomic efficiency signifying potentiality to uphold efficient nitrogen use and environmental sustainability. Thus, addition of biochar in acidic soil would be a sustainable option to reduce carbon mineralization and uphold crop productivity.