Assessment of Spatial and Temporal Variability of Wheat Yield Using Remotely Sensed Images with Different Spatial and Spectral Resolutions and Crop Models.

In an effort to reduce the cost of obtaining spatially referenced data and at the same time increase data resolution, farmers are turning to continuous measurement techniques and remote sensing for more accurate within-field variability information.  Yield rates vary spatially and maps produced by the yield monitor systems are evidence of the degree of within-field variability. The magnitude of this variability is a good indication of the suitability of implementing a spatially variable management plan. The objective of this study was to use remote sensing imagery and yield maps to determine the spatial variability and temporal stability of yield in a wheat crop in Mediterranean environment.

Throughout the course of the 4 year experiment, remote sensing images were acquired from different sources and different spatial and spectral resolutions. The satellite images were from IKONOS and RapidEye. The spatial scale of the images were similar (4 and 5 mt) but RapidEye allowed us to develop vegetation indices based on the Red Edge band which sensitive to plant chlorophyll content. Airbone images were taken on two dates at a fine spatial resolution (75 cm) but coarser spectral visible and NIR bands. All the images where taken in conjunctions with narrow band hyperspectral handheld radiometer field observation.

Yield maps and vegetation indices maps (NDVI, CCCI etc) were highly correlated throughout the years and consistent among remote sensing platforms.  Weather variability effect on yield were assessed using cropm models. The weather affected the stability of yield with variation in the spatial patterns.