Thermal infrared data can potentially improve crop yield estimates through detection of different crop stress levels. Jackson, et al. (1977) have used thermal data in detecting different levels of moisture stress. An accumulated sum of the crop-air temperature difference through the growing season is indicative of different moisture stress levels and, consequently, wheat yields. Various other studies on different crops have arrived at similar results (Reginato, 1978).
Little work has been conducted relating satellite thermal data to moisture stress conditions. One important reason is that the spatial resolution of present satellite thermal data is quite large. For example, one pixel from HCMM (Heat Capacity Mapping Mission) would correspond to 25 hectares (62 acres), and HCMM has the best spatial resolution of the present sensors. Therefore, to evaluate moisture conditions in small commercial fields, relationships need to be determined between moisture conditions in the smaller, nearby commercial cultivated fields. To do this the thermal IR-soil moisture relationship in pasture and wheat is being studied from three different levels---ground, aircraft, and satellite---in a region where both wheat and pasture are common. Prior to this study there has been little effort to use thermal infrared systems over rangeland. Most studies of rangeland growing conditions have been conducted using the visible/near infrared sensors (Deering, et al. 1976).
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