A framework for refining nitrogen management in dry direct-seeded rice using GreenSeeker™ optical sensor

• Site-specific N management using GreenSeekerTM was evaluated in direct-seeded rice.
• Panicle initiation is the appropriate stage to make corrective N management.
• Two algorithms for N management based on GreenSeekerTM proposed in this study.
• The proposed algorithms could maintain high grain yield and high N-use efficiency.

To reduce the amount of wasted reactive nitrogen (N) reaching the environment and to achieve high N fertilizer use efficiency, a site-specific N management strategy using GreenSeeker™ optical sensor (GS) was evaluated in dry direct-seeded rice (DDSR) in the north-western India. Four field experiments were conducted during 2011–2013 to develop an optical sensor algorithm for fine tuning in-season N fertilizer applications. It was demonstrated that panicle initiation of rice is the appropriate stage for applying GS guided N fertilizer dose. Application of a prescriptive dose of 60 kg N ha−1 in two or 90 kg N ha−1 in two or three equal split doses, followed by a corrective N dose guided by GS at panicle initiation stage resulted in rice yield levels comparable to that obtained by following general recommendation, but with lower total N fertilizer application. On an average, N use efficiency was improved by more than 12% when N fertilizer management was guided by GS as compared to when general N fertilizer recommendation was followed. The results prove the inadequacy of general recommendations for N fertilizer management in DDSR and possibility of increasing N use efficiency along with high rice yield levels through site-specific N fertilizer management using GS.