Abstract:Soil nitrogen is important to crop production. The lower nitrogen efficiency is mainly caused by the reason that the nitrogen is commonly applied untimely or non-appropriately. In order to take advantage of winter wheat canopy spectra synchronous implementation indirectly and rapidly diagnose soil nitrogen status, experiment with completely randomized block was conducted for two wheat varieties with different nitrogen levels. Soil and plant nitrogen levels and real-time canopy spectra were measured at different growth stages of winter wheat, i.e., the reviving, jointing, booting and filling stages. Mathematical statistical methods were used to analyze the quantitative relationship between soil nitrogen and plant nitrogen, and build a remote monitoring model of soil nitrogen by using the canopy spectral reflectance. The results showed that the canopy spectral reflectance of winter wheat at each growth stage was significantly different from soil nitrogen content with the application of different levels of nitrogen fertilizer. There were significant relationship between soil nitrate nitrogen content, soil available nitrogen content and nitrogen content of winter wheat plants, and the correlation coefficient could exceed 0.72. However, the relationship between soil total nitrogen content and nitrogen content of winter wheat plants was hardly relevant. The spectra parameters of SAVI(1040,680) and RVI(1040,680) were determined to have important relationship with the soil nitrate nitrogen and available nitrogen contents, respectively. Moreover, the monitoring models of soil nitrate nitrogen and available nitrogen contents based on the spectra parameters performed the best with R2≥0.7396 and R2≥0.8100, respectively. The research result would supply some technical reference for the real-time monitor of soil nitrogen in winter wheat fields by using the canopy spectral reflectance.
