Active canopy sensor-based precision N management strategy for rice

China consumes more than 1/3 of global N fertilizers for rice with less than 1/5 of the world rice planting area. As a consequence, N efficiency is low and nitrate pollution risk is high. Developing efficient N management strategies and technologies for rice are therefore needed. Here, we developed an active canopy sensor-based precision N management strategy for rice in Northeast China. Four site-years of field N rate experiments were conducted in 2008 and 2009 in Sanjiang Plain, Heilongjiang, China. The GreenSeeker active sensor was used to collect rice canopy reflectance data at different growth stages. Three on-farm experiments were conducted in 2011 to evaluate the performance of the developed strategy. The results show that the crop sensor can be used to calculate rice yield potential without additional topdressing N application at stem elongation or booting stage. The GreenSeeker-based precision N management strategy has a regional optimum N rate of 90-110 kg N ha^-1 as initial total amount and 45 and 20 % as basal and tillering N application. It uses the crop sensor to estimate the topdressing N rate at stem elongation stage. GreenSeeker-based precision management and chlorophyll meter-based site-specific N management increased the partial factor productivity of farmers by 48 and 65 %, respectively, without significant change in grain yield. The crop sensor-based N management strategy can therefore improve N use efficiency of rice. It is more suitable for practical on-farm applications, and will contribute to the sustainable development of rice farming.