Relationships between remotely sensed reflectance data and cotton growth and yield

摘要

Remotely sensed electromagnetic reflectance data can provide at relatively low cost a set of detailed, spatially distributed data on plant growth and development. Vegetation indices based on algebraic combinations of different wavelength bands are especially useful in summarizing reflectance data. One of the most commonly used vegetation indices is the normalized difference vegetation index, or NDVI. The objective of this study was to determine whether measurements based on the NDVI could provide information useful for site-specific management of cotton. Aerial photographs were taken of replicated Acala cotton field experiments in California in which the treatment was water or nitrogen stress level. NDVI integrated over time showed a significant correlation with lint yield in those experiments in which there was a significant stress effect on yield. The spatiotemporal pattern of NDVI reflected stress factors and was approximately coincident with the onset of measurable water stress. NDVI tended to indicate the presence of nitrogen stress even in those cases where the stress did not result in a significant yield reduction. In a study of the correlation of NDVI with late season plant mapping indices NDVI was correlated with nodes above white flower and strongly correlated with nodes above cracked boll. An alternative vegetation index, the relative nitrogen vegetation index, was not better than NDVI as an indicator of nitrogen stress.