基于遥感信息的棉花生长调节剂施用方法研究

Cotton is a perennial plant with indeterminate growth characteristics. Management of vegetative growth and reproductive growth is the key to obtain high yield and high quality cotton. Plant growth regulators such mepiquat chloride are essential tool used for controlling excess vegetative growth. Improper application time and rates of mepiquate chloride that resulting farmers’ income and cotton yield decreasing are the main questions in the use of mepiquate chloride. Taking into the fact that the field indicators for the applications of mepiquate chloride can be monitored by remote sensing techniques, the study intends to construct a set of methods for precision applications of mepiquat chloride using remote sensing data. First, water-controlled and nitrogen-controlled field experiments are implemented to obtain the different growth condition cotton, and the rates of mepiquat chloride applications at different cotton growth stages are determined through expert knowledge. Then the function relations between the rates of mepiquat chloride applications and the field indicators for mepiquat chloride applications are constructed, and the quantitative relations between the field indicators for mepiquat chloride applications and spectral variables are determined. The type of proper field indicators and the proper spectral variables for the determination of the rates of mepiquat chloride applications are chosen by these relationships, and the direct quantitative relationships between the rates of mepiquat chloride applications and spectral variables are developed. Finally, the proposed methods for mepiquat chloride applications by remote sensing data are tested by the controlled experiments of precise and extensive mepiquat chloride applications and the regional scale demonstration experiments based on remote sensing monitoring results. The study will provide theoretical and technical support for the precise applications of mepiquat chloride at large area scale.

棉花具有无限生长的独特特性，缩节胺作为应用最为广泛的生长调节剂是协调棉株营养生长与生殖生长从而获得棉花高产、优质的关键。然而实际应用中，因缩节胺的粗放施用导致棉农减产减收的现象较为普遍。针对缩节胺施用多通过株高、叶片色素含量及叶面积指数等遥感技术可反演的依据指标来判定施用量这一特点，本研究拟构建一套基于遥感信息的缩节胺精准施用方法体系。首先通过小区水肥控制试验获取具有不同长势的棉花植株样本，依据专家知识确定不同试验小区缩节胺合理施用量，建立缩节胺施用依据指标与施用量间的函数关系及依据指标与光谱变量间的定量关系，并依此筛选确定不同施用期判定缩节胺施用量的最适依据指标和光谱变量类型，建立光谱变量与施用量间的对应关系；最后通过小区缩节胺的粗放和精准施用对照试验以及基于卫星遥感数据的区域尺度示范应用试验，对基于遥感信息的缩节胺施用判定方法进行评价。该研究将为缩节胺大尺度精准应用提供理论和技术支持。

棉花具有无限生长的独特特性，缩节胺作为应用最为广泛的生长调节剂是协调棉株营养生长与生殖生长从而获得棉花高产、优质的关键。然而实际应用中，因缩节胺的粗放施用导致棉农减产减收的现象较为普遍。针对缩节胺施用多通过株高、叶片色素含量及叶面积指数等遥感技术可反演的依据指标来判定施用量这一特点，本研究拟构建一套基于遥感信息的缩节胺精准施用方法体系。首先通过小区水肥控制试验获取具有不同长势的棉花植株样本，依据专家知识确定不同试验小区缩节胺合理施用量，建立缩节胺施用依据指标与施用量间的函数关系及依据指标与光谱变量间的定量关系，并依此筛选确定不同施用期判定缩节胺施用量的最适依据指标和光谱变量类型，建立光谱变量与施用量间的对应关系；最后通过小区缩节胺的粗放和精准施用对照试验以及基于卫星遥感数据的区域尺度示范应用试验，对基于遥感信息的缩节胺施用判定方法进行评价。获取的观测数据主要有观测点经纬度、棉花冠层光谱、叶面积指数、株高、节间距、叶片数、花蕾数以及叶片鲜重、干重，同时进行了叶片叶绿素含量测定；调查的数据类型包括每个样点区棉花种植品种、播种时间、已施用缩节胺量、灌水量、施肥量以及最终产量数据和农户信息等。遥感影像数据方面，下载获取了2017年及2018年棉花不同生育期Sentinel-2哨兵多光谱遥感卫星数据。利用获取数据明确了：（1）棉花冠层及Sentinel-2植被指数随棉花发育进程的变化特征，结果表明Sentinel-2多光谱反射率与实测冠层光谱反射率变化趋势呈现一致，两者在可见光波段吻合较好，同时基于Sentinel-2多光谱遥感卫星数据提取的NDVI，SAVI，EVIEVI三种最常用于作物发育期及长势监测的指数，EVI指数相比NDVI和SAVI随作物发育进程变化最为稳定；（2）基于Sentinel-2多光谱卫星数据的棉花LAI监测结果表明，基于Sentinel-2多光谱遥感数据的红边参数波段及近红外波段对LAI的估算精度与基于最适植被指数的LAI估算模型的精度相当，对比多种植被指数对不同发育期棉花LAI估算精度发现，EVI及MSAVI2指数估算精度最高。