Biochemical constituents indicate carbon mineralization under a long-term integrated nutrient-supplied Typic Kandiustalf

We investigate the long-term impact of integrated nutrient management to study the influence of fertilizer and manure on different biochemical constituents and carbon mineralization of roots and stubble of finger millet (Eleusine coracana L.) at the Experimental Farm, University of Agricultural Sciences, Bangalore, India. The farm continuously received uniform treatments for 40-years during 1978-2018 under a groundnut + finger millet cropping system. Cellulose, hemicellulose, and ash contents for roots and stubble were recorded higher with the treatment T-5 [farmyard manure (FYM) at 10 t ha(-1) + 100% recommended dose of fertilizers (RDF)] while the control treatment showed their lowest values. The treatment T-5 caused a higher cumulative rate of CO2 evolution from roots (49.68 mg CO2 g(-1) C) and stubble (58.48 mg CO2 g(-1) C) at the 98th day of incubation following a sigmoid curve pattern for the carbon mineralization. The correlation was highly significant between the rate of decomposition and cellulose content for roots (r = 0.892*) and stubble (r = 0.947**). Unlikely, the correlation was negatively significant between the decomposition rate and the lignin content in roots (r = -0.745*) and stubble (r = -0.720*). We conclude that the combined application of FYM at 10 t ha(-1) and 100% RDF is the most efficient treatment to increase saccharification, reduce lignification, and sequester a higher rate of carbon mineralization capable of preserving the soil organic carbon (SOC) and facilitating alluviation of more resistant carbon in a Typic Kandiustalf soil.

Automated summary

The study highlights the significant impact of integrated nutrient management on the biochemical constituents and carbon mineralization of finger millet roots and stubble. The combined application of farmyard manure and recommended dose of fertilizers was found to enhance saccharification, reduce lignification, and increase the rate of carbon mineralization, thus promoting soil organic carbon preservation.