Optimization of nitrogen management reduce nitrogen stress and enhance productivity of super- seeder sown wheat under rice residue incorporation

Abstract The in-situ management of rice straw incorporation is now an essential practice in the rice-wheat cropping system with the growing adoption of super-seeder among farmers. This machinery has made it easier to incorporate rice residues into the soil, crushing and spreading straw evenly for cleaner cultivation. However, the effect of nutrient immobilization due to incorporation of massive organic residues at the initial stage of the decomposition is a major constraint for enhancing yield and productivity. This study investigates the effect of bio-decomposer, nitrogen (N) level, and N scheduling on N immobilization status, dry matter, N accumulation, remobilization, productivity and soil quality variables in super-seeder sown wheat for two consecutive years (2020-21 and 2021-22). The experiment was laid in split-split-plot design without (B0) and with (B1) application of bio-decomposer in main plot and two nitrogen levels 150 (N1) and 180 (N2) kg ha -1 in sub-plot; and three N splits (%) viz ., 50: 25:25 (S1), 40: 30: 30 (S2), and 30 :35:35 (S3) in sub-sub-plot and replicated thrice. N concentration and uptake at pre- and post-anthesis were recorded significantly higher with N2 and S1 compared to N1 and S2 and S3 in both years. Post-anthesis N accumulation (post-NA) and N remobilization (NR) with N2 was significantly higher to the tune of 22% and 17% than N1. Dry matter accumulation (DMA) at anthesis and harvest with N2 was significantly higher by 5.7%, while with S1 there is an improvement of 6.2% over S3. The grain yield with N2 and S1 significantly improved by 8.3% and 10.9% (two years mean) compared to N1 and S3, respectively. Soil urease activity (UA) was significantly enhanced with the application of microbial formulation (bio-decomposer), N2, and S1 in comparison to B0, N1 and S3 at 30 and 60 DAS (days after sowing). Besides, use of bio-decomposer also improved soil microbial biomass carbon (SMBC). Hence, the present study revealed that the application of higher N level coupled with higher proportion of basal N resulted in overcoming N stress and could be propounded for sustainable production and higher productivity. The result presented here assumes great significance in proper utilization and conservation of rice residue under rice-wheat cropping system.