Effects of different nitrogen treatments on the relationship between flag leaves spectral characteristic and SPAD and IPAR in hybrid rice varieties

In order to study the effects of different nitrogen treatments on the relationship between spectral features of flag leaves and the SPAD, and IPAR in hybrid rice, this experiment was conducted with two-line hybrid rice cultivars, Quanliangyou 1 and Quanliangyou 681 with three application levels of nitrogen fertilizer including N0 (0 kg · hm^-2), N1 (150 kg · hm^-2) and N2 (250 kg · hm^-2), respectively. The results showed that there was significant difference in the flag leaves spectral features of the two varieties under different nitrogen treatments. The spectral reflectance of the flag leaves was gradually getting bigger in the visible region and smaller in the near infrared region at full heading stage. The SPAD value, PRI and IPAR of the two varieties significantly increased with the improvement of nitrogen rates, and the correlation index between PRI and IPAR was significant, at 0.64. Additionally, both the spectral index DVI and PVI were positively correlated with grain yield, at 0.82 and 0.86, respectively. Given this situation, these spectral indexes of flag leaves in hybrid rice mentioned in our studies could be used to predict grain yield and IPAR. In this study, the acquisition of reflectance spectra based monitoring of nitrogen nutrition in leaf can be applied to precise nitrogen management, and to improve nitrogen use efficiency, thereby providing theoretical guidance for achieving high yield and efficiency in production. (authors)