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为研究冠层归一化差值植被指数(Normalized difference vegetation index,NDVI)在棉花重要生育时期估算棉花产量的可行性,使用GreenSeeker分别对不同灌水施肥条件下棉花光谱反射率NDVI值进行测定优化,建立NDVI值与产量关系数学模型,并对模型精度进行验证。结果显示:不同水氮组合随着生育期的推移棉花冠层NDVI值变化趋势基本一致,都呈“低-高-低”的变化规律;选取在棉花出苗后80、105和140d冠层NDVI值分别与产量进行相关性分析,得出冠层NDVI值与产量具有明显的正相关关系,相关系数分别为R2=0.376 0,0.093 4,0.363 9。利用独立的试验数据对相关性最高的水氮组合棉花出苗后80d的产量模型进行模型验证,其相关系数R2=0.712 6,均方根误差(Root mean square error,RMSE)561.04kg/hm2。因此,棉花出苗后80d的冠层NDVI值可以估测棉花产量。
In order to study the feasibility of estimating normalized difference vegetation index (NDVI) in cotton during its important growth period, GreenSeeker was used to determine and optimize the spectral reflectance (NDVI) of cotton under different irrigation and fertilization conditions. Establish the mathematical model of the relationship between NDVI value and yield, and verify the model accuracy. The results showed that the NDVI values of cotton canopy under the different growth stages were basically the same, showing “low - high - low”. The changes of cotton NDVI at the 80th, the 105th and the 140th days after cotton emergence NDVI value and yield were analyzed respectively. The results showed that there was a significant positive correlation between canopy NDVI value and yield, the correlation coefficients were R2 = 0.376 0,0.093 4,0.363 9 respectively. The independent experimental data were used to validate the yield model 80d after the emergence of the most relevant water-nitrogen combination cotton with the correlation coefficient R2 = 0.712 6 and root mean square error (RMSE) 561.04kg / hm2. Therefore, the canopy NDVI value of cotton 80 days after emergence can estimate the cotton yield.