Reliance on inorganic fertilizers with less or no use of organic fertilizers has impaired the productivity of soils worldwide. Therefore, the present study was conducted to quantify the effects of integrated nutrient management on rice yield, nutrient use efficiency, soil fertility, and carbon (C) sequestration in cultivated land. The experiment was designed with seven treatments comprising of a zero input control, recommended inorganic fertilizers (RD), poultry manure (PM) (5 t ha-1) + 50% RD, PM (2.5 t ha-1) + 75% RD, vermicompost (VC) (5 t ha-1) + 50% RD, VC (2.5 t ha-1) + 75% RD, and farmers' practice (FP) with three replications that were laid out in a randomized complete block design. The highest grain yield (6.16-6.27 t ha-1) was attained when VC and PM were applied at the rate of 2.5 t ha-1 along with 75% RD. Uptake of nutrients and their subsequent use efficiencies appeared higher and satisfactory from the combined application of organic and inorganic fertilizers. The addition of organic fertilizer significantly influenced the organic carbon, total carbon, total nitrogen, ammonium nitrogen, nitrate nitrogen, soil pH, phosphorus, potassium, sulfur, calcium, and magnesium contents in post-harvest soil, which indicated enhancement of soil fertility. The maximum value of the organic carbon stock (18.70 t ha-1), total carbon stock (20.81 t ha-1), and organic carbon sequestration (1.75 t ha-1) was observed in poultry manure at the rate of 5 t ha-1 with 50% RD. The soil bulk density decreased slightly more than that of the control, which indicated the improvement of the physical properties of soil using organic manures. Therefore, regular nourishment of soil with organic and inorganic fertilizers might help rejuvenate the soils and ensure agricultural sustainability.
Keywords: carbon sequestration; nutrient-use efficiency; poultry manure; rice yield; soil fertility; vermicompost.