基于GreenSeeker的冬小麦NDVI分析与产量估算

摘要

以2007-2009年连续2个冬小麦生长季的田间试验数据为基础,利用GreenSeeker获取冠层归一化差值植被指数(NDVI),分别对不同氮营养条件下冬小麦的产量变化、冠层NDVI值随施氮量和生育期的动态变化,以及NDVI与产量的相关性定量分析,建立基于NDVI的冬小麦产量估算模型.结果表明,冬小麦的产量变化随施氮量的增加呈抛物线趋势变化;冠层NDVI在返青期前随施氮量增加基本不变,返青期至灌浆初期随施氮量增加呈显著增加趋势;整个生育期冠层NDVI呈现“低-高-低”变化趋势.冬小麦整个生育期不同施氮水平下的NDVI值与产量的相关性均为正相关关系,且相关性随生育期逐渐增强,在灌浆末期达到最大.利用NDVI建立的冬小麦产量估算模型,以灌浆初期(P=0.005)和灌浆末期(P＜0.001)的模型达到极显著水平.经验证,灌浆初期的冬小麦产量预测值与实测值的回归关系达到了显著水平(P=0.0129),灌浆末期则达到极显著水平(P=0.0002).因此,利用灌浆初期和灌浆末期的NDVI值可以预测冬小麦产量,尤以灌浆末期预测效果更佳.%The field experiment was carried out in two winter wheat growing seasons during 2007-2009. Winter wheat canopy reflectances in the 656 nm and 770 nm wavelengths were obtained by GreenSeeker at over-wintering stage, reviving stage, jointing stage, early-filling stage, and last-filling stage, respectively, in order to compute NDVI [(NIR770-R656)/(NIR770+R656)]. Yields were collected at harvest stage and compared among different nitrogen application rates. Canopy NDVI changes were analyzed with nitrogen increasing and growth, respectively. Furthermore, correlation analysis was done between yield and canopy NDVI. Yield estimation models were established for winter wheat based on canopy NDVI. Results showed that, winter wheat yield changed in parabola shape with N increasing. Wheat canopy NDVI value presented almost changeless before reviving stage, but great increase from reviving stage to early-filling stage with N increasing. In the whole growth stage, canopy NDVI value presented a trend of "low-high-low". The correlation between canopy NDVI and yield was positive in the whole growth stage with different N rates and gradually became higher with growth, and up to the highest at the late-filling stage. The yield estimation models based on canopy NDVI at early-filling stage (P=0.005) and late-filling stage (P<0.001) were greatly significant. Regression validated between predicted and measured values was significant at early-filling stage (P=0.0129) and greatly significant at late-filling stage (P=0.0002). Therefore, it is feasible that using canopy NDVI at early-filling stage and late-filling stage estimates winter wheat yield, especially at late-filling stage.