Assessing rice residue and nitrogen management strategies on productivity and nitrogen use efficiency of wheat in rice-wheat cropping system in Indo-Gangetic Plains

Context: Rice-wheat cropping system produces ample scattered rice residue in the field after mechanical harvesting which holds no economic value for the farmers in the Indo-Gangetic Plains (IGP) of South Asia. Several options are available for managing rice residue, enabling wheat seeding in the succeeding season to avoid its burning. However, limited information is available on the efficient nitrogen management practices under different rice residue management options to achieve higher wheat productivity and N use efficiency (NUE). Objective: This two-year study (2020-2022) aimed to evaluate the effect of time and method of fertilizer N application under different rice residue management options on canopy temperature, wheat yield and NUE on two texturally different soils. Methods: Field experiment was conducted in a split-plot design on two texturally different soils (sandy loam and clay loam). Treatments in the main plots included four different tillage and residue management (TRM) options; zero tillage with rice residue as mulch using Happy Seeder (ZTRM), minimum tillage with partial incorporation of residue using super seeder (MTRI), residue incorporation using mould board plough (MBRI), and conventional tillage after complete removal of residue (CTR0), and six fertilizer N management options (time and method of applications) including no N control in subplots. Results: ZTRM significantly reduced canopy temperature (CT) at the grain development stage compared to residue removal (CTR0) on both soil types. ZTRM resulted in mean yield increase of 2.2% (2 yrs mean) over CTR0 on both soils. Among TRM options, CTR0 recorded the lowest NUE indices. Across the soils, ZTRM showed significantly higher values of agronomic efficiency (14.1 kg grain kg-1 N), recovery efficiency (43.3 %) and physiological efficiency (27.4 kg grain kg-1 N uptake) of applied N compared to the other TRM options on sandy loam with similar trend on clay loam. Application of 132 kg N ha-1 (N4) to wheat (24 kg at sowing, 96 kg top dressed at 1st and 2nd irrigation followed by three foliar sprays of 4% urea) resulted in 76.5% and 49.6% increase in grain yield over no-N control in sandy loam and clay loam, respectively. The N4 recorded significantly higher N uptake and NUE in wheat compared to the other modes of fertilizer N application, irrespective of residue management option. Conclusions: Zero tillage with rice residue as mulch using Happy Seeder and soil application of 120 kg N ha-1 in three splits along with 12 kg N ha-1 as three foliar sprays of 4% urea solution are viable option to achieve higher wheat productivity and NUE in wheat to avoid rice residue burning in North-West IGP of India. Implications: This study revealed a paradigm approach for attaining higher productivity and N-use efficiency of wheat while preventing environmental consequences associated with residue burning and climate change in the Indo-Gangetic Plains of South Asia.