Assessment of conservation agriculture on soil nutrient’s stratification ratio, carbon sequestration rate, management indices and crop productivity in Southern Telangana India

The impending crisis for food production is the biggest threat to sustenance of soil resources due to industrial farming practices adopted by multitudes of farmers on all parts of the world inclusive of the Southern Telangana Zone (STZ) in India. This can extensively degrade the soil if not substituted by soil resource-saving agricultural systems. This present experiment is implemented to assess the impact of contrasting tillage practices and weed management practices on soil nutrient stratification ratio (SR), carbon sequestration rate (CSR), carbon management indices (CMI), carbon retention efficiency (CRE) and monitor the grain yield of maize after three-years in CA with a cotton-maize-Sesbania rostrata cropping system. Three tillage practices (main-plots) included the T₁:Conventional tillage with cotton- Conventional tillage with maize- fallow i.e., No Sesbania rostrata (Farmers' practice), T₂:Conventional tillage with cotton- Zero tillage with maize- Zero tillage with Sesbania rostrata and T₃: Zero tillage with cotton + Sesbania rostrata residues- Zero tillage with maize + Cotton residues- Zero tillage with Sesbania rostrata + Maize stubbles. Weed management tactics (Sub plots) were W₁: Chemical weed control, W₂: Herbicide rotation, W₃: Integrated weed management and W₄: Single hand-weeded control. Sampling of the soil in the 0 - 15 and 15-30 cm, subsequent to harvesting of maize was analyzed for pH, EC, soil macronutrient's availability, soil organic carbon (SOC), and computed for soil nutrients SR, CSR, CMI and CRE duly following the standard analytical procedures. The results indicated that in the 0-15 cm, 15.3% of SOC, 15.1% of available soil N, 19.6% of available soil P and SR of 1.20 for SOC were higher under T₃ relative to T₁. Similarly, 58.1% of cumulative CSR, 58.8% of CRE in the 0-30 cm, and 30.3% of CMI in the 15-30 cm were higher under T₃ compared to T₁. The passive pool of carbon (C_PSV) was the dominant contributor of SOC to total SOC in the 0-30 cm soil layer. The T₃ had higher Kernel yield (11.6%) in comparison T₁. Kernel yield was also 23.4-43.1% higher under W₁, W₂, W₃ over W₄. These findings suggest that adoption of zero tillage (ZT) with crop residue retention (T₃), IWM and chemical weed control/ herbicide(s) could be a viable solution for improving the soil health and contributing towards enhanced crop productivity in cotton-maize-Sesbania rostrata cropping system in this zone.