Field evaluation of slow-release nitrogen fertilizers and real-time nitrogen management tools to improve grain yield and nitrogen use efficiency of spring maize in Nepal

Several innovative fertilizers and application methods, along with different decision support tools have been developed to improve nitrogen use efficiency (NUE) and crop yields, but their comparative study in maize is yet to be done in Nepal. Thus, we evaluated different slow-release N fertilizers and decision-making tools for real-time N management compared with the common urea on their effectiveness in increasing NUE, grain yield and economic return of spring maize (Zea mays L. cv. Rampur Hybrid-10). A field trial was conducted at Dang Valley of Nepal in a Randomized complete block design with three replications and seven treatments; N omission- (0 kg N ha−1), normal urea at 120 kg N ha−1 (recommended dose, N120), and 180 kg N ha−1(N180), Polymer Coated Urea (PCU- 90 kg N ha−1), Urea Briquette-deep placement (UDP- 90 kg N ha−1), GreenSeeker (GS- 143 kg N ha−1) and Leaf Color Chart based N management (LCC- 143 kg N ha−1). N application based on decision support tools (LCC and GS) and innovative fertilizers (UDP, PCU) yielded 17.35–45.81% more grain yield than recommended dose (RDF). The real time nitrogen application through LCC and GreenSeeker and slow release N fertilizer (PCU and UDP) resulted in higher agronomic efficiency of nitrogen- AEN (21.30–27.82 kg grain kg−1 N) compared to RDF (12.15 kg grain kg−1 N) and N180 (19.87 kg grain kg−1 N). UDP, with 25% less N compared to RDF, resulted in higher grain yield (5.25 t ha−1), partial factor productivity of N– PFPN (58.37 kg grain kg−1 N) and AEN (27.82 kg grain kg−1 N). Based on the economic return and ease in the application, both UDP and LCC based N application seem promising in Nepalese conditions. However, their effectiveness should be validated across diverse agro-ecologies, soil types and climatic conditions for a general recommendation.