Conservation Agriculture Practices on Carbon Stock, Carbon Sequestration and Soil Biological Properties of Rice-Okra-Green Manure Cropping System

Conservation agriculture-based sustainable crop production intensification must not only reduce the impact of climate change on crop production but also mitigate the factors that cause climate change by reducing emissions and by contributing to carbon sequestration in soil while improving food security and enhanced productivity of resources. The present study explores the carbon stock, soil carbon sequestration potential and changes in physical, chemical and biological properties of soil due to conservation agriculture practices. Field experiments were conducted in the Agronomy Farm, College of Agriculture, Vellanikkara, from May 2019 to March 2021to study the effect of conservation agriculture (CA) practiceson carbon stock, carbon sequestration and soil biological properties. Rice-okra-green manure cropping system with conservation practice were compared with rice - okra cropping system without conservation practices, keeping the same layout for two years. Conservation agriculture practices had a significant influence on carbon stock, carbon sequestration and soil biological properties. After six cropping sequences, conservation practices such as direct sowing rice in flat bed + green manuring- okra+ crop residue mulch-cowpea had the maximum soil carbon sequestration of 9.52 Mg ha-1and 6.03 Mg ha-1, at 15 and 30 cm soil depth, followed by direct seeding rice in flat bed + brown manuring- okra+ crop residue mulch-cowpea (10.17,6.07 Mg ha-1). The treatments with out conservation agriculture practices, such as direct seeding rice in flat beds - okra-fallow, had a negative sequestration value. The highest microbial biomass carbon 134.83μg g-1) was recorded in direct seeding rice in flat bed + brown manuring - okra + crop residue mulch-cowpea. Dehydrogenase activity was found to be significantly highest in direct seeding rice in flat bed + brown manuring - okra + crop residue mulch-cowpea (57.17 μg TPF g-1 soilday-1) and it was on par with direct seeding rice in flat bed + green manuring –okra + crop residue mulch-cowpea (T4) (57.17 μg TPF g-1 soilday-1).