Nitrogen use efficiency of rice in India: A regional analysis

The crop nitrogen (N) use efficiency has been recognized as a useful indicator to measure the overall progress of the country towards achieving the sustainable development goal. Moreover, national level N use efficiency indicators are essential for improved estimate of global N budget and environmental impact assessment. We made an attempt to calculate the indicators of N use efficiency for rice at national and regional level in India. We utilized the data from research papers (23 no) published in reputed scientific journals and theses (83 no) submitted to different state agricultural universities over a period of 46 years (between 1972 and 2018). The partial factor productivity of N for rice in India ranged from 39.8 to 68.0 kg kg(-1) with a national average value of 52.8 kg kg(-1). The national average agronomic N use efficiency and nitrogen recovery efficiency (REN) were 18 kg kg(-1) and 42.6%, respectively. Conducive agro-climatic condition coupled with improved crop management resulted in higher REN (>50%) in northern zone states of India. Whereas, rain-fed eastern and central zone states have REN<40%. The partial N balance (PNB) in rice ranged from 0.72-1.42 in India. The states with lower PNB need to reconcile their N addition with crop N uptake by adopting N responsive varieties and advanced fertilizer management to prevent environment degradation and economic loss. The findings of this study have significant implications for N budget estimation and policy decisions on hunger, food security and environment at national and global level.