玉米氮营养指数的高光谱计算模型

快速、准确、动态地诊断大面积玉米氮营养状态对于评价玉米长势、预测产量和指导农业生产均具有重要的意义。该研究利用北京昌平、长春市西北市郊的四间房村2个试验区的玉米冠层高光谱数据演变得到的多种光谱参数，采用逐步回归分析方法，建立了玉米氮营养指数与高光谱参数的定量关系，提出了玉米氮营养指数的敏感光谱参数及预测方程。研究结果显示，红边/绿边比值参数、红边/近红外比值参数、红边敏感点参数与玉米氮营养指数高度相关，是诊断玉米氮营养指数的敏感光谱参数。通径分析得到红边/绿边比值参数、红边/近红外比值参数与玉米氮营养指数的通径系数分别为-0.14942和-0.35218，表明玉米氮营养指数对红边/绿边比值参数、红边/近红外比值参数有间接影响，红边敏感点参数与玉米氮营养指数的通径系数为1.41549，表明红边敏感点参数对玉米的氮营养指数高度敏感。基于敏感光谱参数的玉米氮营养指数多元回归预测模型的相关系数R为0.95507，观测值与拟合值的拟合误差小于0.1，均方根误差为0.06016，F值达到了167.727，显著水平P为0.0045。由此可以得出利用敏感光谱参数定量分析玉米氮营养指数是可行的。

Model for calculating corn nitrogen nutrition index using hyper-spectral data

A method to fastly, accurately and dynamicly diagnose nitrogen nutrition status in large acreage is essential for corn growth vigor evaluation, production prediction and agriculture management. Two study sites respectively located in Changping district of Beijing and Changchun city were investigated and multiple spectral parameters were derived from the hyper-spectral data of the corn canopy of the two study areas. Further, based on stepwise regression analysis, quantitative relation between the corn nitrogen nutrition index (NNI) and hyper-spectral parameters was established, and the hyper-spectral parameters which had distinct correlation with the corn NNI as well as the predictive equations were presented. The results showed that three hyper-spectral parameters, i.e. NIR/G, NIR/NIR and REIP, were highly correlated with the corn NNI. Path coefficients of NIR/G and NIR/NIR to the corn NNI were calculated to be -0.14942 and -0.35218 respectively, which indicated an indirect effect of the two hyper-spectral parameters on the corn NNI. The path coefficient of REIP to the corn NNI was 1.41549, which revealed that REIP was highly sensitive to the corn NNI. The correlation index of the multi-variant regression model for the distinct hyper-spectral parameters and the corn NNI was 0.95507, fitting error between predicted and measured valuse was less than 0.1, Root mean square error was 0.06016, F value was 167.727 and P value was 0.0045.