Effects of two kinds of variable-rate nitrogen application strategies on the production of winter wheat (Triticum aestivum)

To improve nitrogen-use efficiency (NUE) is crucial to agriculture; it benefits agricultural production and reduces the impact on the environment. In past decades, a lot of variable-rate nitrogen (VRN) application strategies have been proposed to improve NUE. The concern of this study is whether the specific N management strategy based on using in-season predicted grain yield (ISPGY) and in-season N uptake (ISNU) is more efficient than the VRN strategy based on grain yield goal (GYG) and ISNU. For this purpose, 2-year (2005-06 and 2006-07) winter wheat (Triticum aestivum) experiments with the cultivar 'Jingdong8' were conducted at the China National Experimental Station for Precision Agriculture, located in the Changping district of Beijing, China. Four VRN application methods, SPAD chlorophyll meter method 1 (SCM1), SPAD chlorophyll meter method 2 (SCM2), vegetation index method 1 (VI1), and vegetation index method 2 (VI2), were compared with a random block design with 10 replications. The differences between SCM1 and SCM2 and between VI1 and VI2 were used to estimate the potential grain yield for each plot. SCM1 and VI1 used ISPGY, whereas SCM2 and VI2 adopted GYG. Economic benefits and soil residual NO3-N were analysed for the four methods. The results showed that the SCM2 and VI2 performed better than the corresponding SCM1 and VI1, indicating that the GYG-based VRN strategy is better than the ISPGY-based VRN strategy for conducting specific N management.