Crop and water productivity, energy auditing, carbon footprints and soil health indicators of Bt-cotton transplanting led system intensification

Direct-seeded-cotton (DSC) leads to low crop and water productivity and energy-output with higher carbon-footprints besides impairing system-intensification under conventional cotton-wheat cropping system (CWCS). Hence, we evaluated two methods of Bt-cotton establishment [transplanted cotton (TPC) & DSC)] at three planting geometries/densities in four Bt-cotton based cropping-systems [DSC-wheat (DSC-W), TPC-wheat-mungbean (TPC-W-M), DSC-onion (DSC-O), TPC-onion-fodder cowpea + fodder maize (TPC-O-FC + FM)] in semi-arid region of south Asia. Poly-glass nursery-raised TPC exhibited significantly higher germination (96.5%), seedling-survival (96.1%) and 14.1% higher plant-stand owing to lower seedling-mortality (3.2%). TPC used ∼60% less irrigation-water but exhibited significantly higher seed-cotton, seed and lint yield, net-returns, radiation-use-efficiency and water-productivity by 11.4, 9.9, 14.3, 17.3, 10.7 and 260.6%, respectively over DSC. Planting geometry/density of 60 × 45 cm (37,037 plants ha−1) exhibited significantly higher crop and water productivity and economic-returns. Bt-cotton transplanting led system-intensification enhanced the system-productivity (26.1%), profitability (30.5%), water-productivity (19.3%) and land-use-efficiency (8.5%) over the DSC-based systems with significantly higher values under TPC-O-FC + FM. Energy-use pattern reveled that farm inputs viz. Fertilizers (54–60%), water (15–25%) and diesel (6–10%) consumed bulk of the input-energy in different cropping systems with greatest values under TPC-O-FC + FM. TPC-W-M exhibited highest system energy-output (604.6 × 103 MJ ha−1) and energy-returns (566.2 × 103 MJ ha−1). TPC-O-FC + FM exhibited significantly higher carbon-consumption (668.9 kg CE ha−1) and carbon-output (21431.3 kg CE ha−1) while maintaining significantly higher carbon-efficiency (32.0) and carbon sustainability index (31.0). TPC-O-FC + FM had least carbon-footprints (0.07 kg CE kg−1 SCEY) while conventional-CWCS exhibited 2-folds higher carbon-footprints. Legume-imbedded TPC-based cropping systems markedly increased the soil physical (bulk-density, water-stable-aggregates), chemical (SOC, available-NPK) and biological properties (soil-microbial-biomass-carbon, dehydrogenase and ergosterol activity) over the conventional CWCS and DCS-O systems. Overall, Bt-cotton transplanting led system-intensification upholds great importance in enhancing the system crop and water-productivity, profitability, energy-productivity, resource-use-efficiency and soil-health with minimal carbon-footprints in semi-arid agro-ecosystems of south Asia.