Chin J Plan Ecolo ›› 2006, Vol. 30 ›› Issue (6): 983-990.doi: 10.17521/cjpe.2006.0126
• Research Articles •
ZHU Yan; YAO Xia; TIAN Yong_Chao; ZHOU Dong_Qin; LI Ying_Xue; CAO Wei_Xing*
Background and Aims Nitrogen accumulation in cereal crops is a key parameter for assessing plant growth status and predicting grain yield and quality. Non-destructive monitoring and diagnosis of plant nitrogen status is necessary for precise nitrogen management. The present study was conducted to determine the quantitative relationships of leaf nitrogen accumulation to canopy reflectance spectra in both rice and wheat crops.
Methods Ground-based canopy spectral reflectance and nitrogen accumulations in leaves were measured in six field experiments consisting of five different rice cultivars, three different wheat cultivars and varied nitrogen levels across six growing seasons. All possible ratio vegetation indices (RVI), difference vegetation indices (DVI) and normalized difference vegetation indices (NDVI) of sixteen wavebands from the MSR_16 radiometer were calculated. Analyses were made to determine the relationships of seasonal canopy spectral reflectance and all possible vegetation indices to leaf nitrogen accumulations in wheat and rice under different nitrogen treatments and cultivars.
Key Results As expected, nitrogen accumulation in rice and wheat leaves increased with increasing nitrogen fertilization rates. The relationship with canopy reflectance, however, was more complicated. In the near infrared portion of the spectrum (760-1 220 nm), canopy spectral reflectance increased with increasing nitrogen supply, while in the visible region (460-710 nm), canopy reflectance decreased with increasing nitrogen supply. For both rice and wheat, leaf nitrogen accumulation was best evaluated at 810 and 870 nm. Among all possible RVIs, DVIs and NDVIs, RVI(870,660) and RVI(810,660) were most highly correlated with leaf nitrogen accumulation in both rice and wheat. In addition, the correlations of RVI(870,660) and RVI(810,660) to leaf nitrogen accumulation were found to be higher than that of individual wavebands at 810 and 870 nm in both rice and wheat.
Conclusions This study indicated that leaf nitrogen accumulation in both rice and wheat can be monitored with common wavelengths and spectral parameters. In addition, the integrated regression equation could be used to describe the dynamic pattern of change of leaf nitrogen accumulation in both rice and wheat with reflectance spectra parameters, although separate regression functions slightly enhanced prediction accuracy.
ZHU Yan, YAO Xia, TIAN Yong-Chao, ZHOU Dong-Qin, LI Ying-Xue, CAO Wei-Xing. QUANTITATIVE RELATIONSHIP BETWEEN LEAF NITROGEN ACCUMULATION AND CANOPY REFLECTANCE SPECTRA IN RICE AND WHEAT[J].Chin J Plan Ecolo, 2006, 30(6): 983-990.
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