Nutrient management and cropping pattern influence the carbon sequestering ability of semi-arid tropical soils

The present investigation assessed the consequences of long-term organic and inorganic nutrient amendments on carbon sequestering potential and biological attributes of Indian semi-arid tropical soils under three different cropping systems. We used soil samples from four long-term nutrient management adoptions, i.e., absolute control, inorganic chemical fertilizer, organic amendments, and a combination of both organics and inorganics (integrated nutrient management), being adopted under irrigated (maize-sunflower), wetland (rice-rice), and dryland (cotton-pearl millet) cropping systems for this investigation. Soil samples collected from these long-term permanent manure experiments were assessed for carbon-sequestering ability and biological attributes, including microbial biomass carbon, labile carbon, protein index, dehydrogenase, and respiration. The results revealed that continuous use of organic amendment (farmyard manure) with or without synthetic fertilizers improves the carbon sequestering potential of soil in all the cropping systems. Integrated nutrient management with rice-rice cropping under wetland conditions had the highest carbon sequestering potential (287 kg carbon per ha per year). In comparison, maize-sunflower under irrigated conditions accounted for 141 kg C per ha per year, and cotton-pearl millet under dryland conditions accounted for 261 kg of carbon per ha per year. Combining organic manure and chemical fertilizer significantly enhanced the soil biological attributes compared with chemical fertilized and unfertilized control soils. The nutrient management and cropping system significantly influenced the soil carbon sequestering ability and, subsequently, the soil biological attributes of semi-arid tropical soils. Hence, continuously adding organic amendments and proper crop residue management is essential to improve tropical soils' carbon sequestering potential and overall health under intensive agriculture.