Real-time application of neem-coated urea for enhancing N-use efficiency and minimizing the yield gap between aerobic direct-seeded and puddled transplanted rice

Abstract

An appropriate nitrogen (N) management strategy is required for minimizing the yield loss incurred in aerobic direct-seeded rice (ADR) due to moisture stress. Field experiments for two consecutive years were conducted to evaluate comparative performance of real-time application of neem-coated urea (NCU) and prilled urea (PU) using a customized leaf color chart (CLCC) on growth, yield and N use efficiency of both ADR and puddled transplanted rice (PTR). Six treatments were tested with cultivar ‘Apo’:0 N (T1) as control, 100 kg N ha􀀀 1 as prilled urea (PU) applied conventionally (T2), 100 kg N ha􀀀 1 as NCU applied conventionally (T3), 100 kg N ha􀀀 1 as PU applied on the basis of CLCC recommendation (T4), 100 kg N ha􀀀 1 as NCU applied on the basis of CLCC recommendation (T5), and 50 kg N ha􀀀 1 as PU and 50 kg N ha􀀀 1 as farm yard manure (FYM) (T6). Results of the field experiments showed significant effects (p ≤ 0.05) of both cultivation method and N management on yield. The ADR produced 22.5–46.0% less yield as compared to PTR mainly due to substantial reductions in leaf area, biomass and sink size. As compared to PU, the conventional application of NCU increased yields by 7.1–13.4 % and 6.8–10.0 %,in ADR and PTR, respectively and the differences were significant (p ≤ 0.05). But when applied using CLCC, yield enhancements from PU increased to 21.2–22.9 % and 14.6–15.9 %, respectively. The NCU resulted in 6.6–8.9 and 6.2–6.5 % higher N recovery efficiency as compared to PU, which was further increased to 16.3–18.0 and 11.4–14.6 % in ADR and PTR, respectively when applied using CLCC. Hence, our results indicate that optimization of N application combining both a real-time N management tool (CLCC) and enhanced efficiency N fertilizer (NCU) could help minimize yield losses, which was more visible under ADR by improving growth and yield parameters. The findings of the present study can be proposed as a suitable alternative to the existing N-fertilizer management for rice farmers of both aerobic dry-seeded and puddled transplanted conditions, while more yield advantage was realized in the former.