Carbon and nitrogen mineralization kinetics as influenced by diversified cropping systems and residue incorporation in Inceptisols of eastern Indo-Gangetic Plain

Carbon (C) and nitrogen (N) mineralization process is a key indicator of soil quality which regulate nutrient availability and supply to the crops. To provide insight on C and N mineralization in soil of diversified cropping systems, an experiment was initiated in split-plot design with five diversified jute-rice based cropping system under four nutrient and crop residue management practices (NCRM) during 2012-13. The five cropping system viz., fallow-rice-rice (F-R-R), jute-rice-wheat (J-R-W), jute-rice-baby corn (J-R-Bc), jute-rice-gardenpea (J-R-Gp), jute-rice-mustard-mung bean/green gram (J-R-M-Mu) were taken in main plot and four (NCRM) practices viz. 75% recommended doses of fertilizers (RDF) to all crops without crop residue (F1R0), 75% RDF with crop residues (F1R1) (Residue of rice, wheat and corn at 4 t/ha and garden pea and mung bean at 2 t/ha incorporated into soil with their respective cropping), 100% RDF without crop residues (F2R0) and 100% RDF with crop residue (F2R1) were taken in sub plot with three replication. Soil samples (0-15 cm) were collected after four year completion of crop cycles in 2016 to measure C and N accumulation and to estimate potentially mineralizable C (C0) and N (N0) using first order kinetic model. The highest C mineralization was recorded in J-R-M-Mu (1280 mg CO2/kg soil) followed by J-R-Gp (1235 mg CO2/kg soil) and J-R-Bc (1235 mg CO2/kg soil) cropping system under F2R1. N mineralization was also higher in J-R-M-Mu (63.3 mg N/kg soil) followed by J-R-Gp (55 mg N/kg soil) and J-R-Bc (52 mg N/kg soil) cropping systems under F2R1.Significantly higher (P < 0.05) rate constant for C and N mineralization (kC and kN) were in J-R-M-Mu under F2R1 compared to other cropping systems and NCRM practices. Hence, our findings indicate that cropping systems with 100% RDF with mungbean residue at 2 t/ha had higher C and N mineralization. This cropping system had also higher C and N kinetic due to presence of more labile or decomposed SOC. Application of mineral fertilizers with crop residues had positive effect on C and N mineralization and their kinetics.