Abstract
Water is an important component in agricultural production for both yield quantity and quality. Although all weather conditions are driving factors in the agricultural sector, the precipitation in rainfed agriculture is the most limiting weather parameter. Water deficit may occur continuously over the total growing period or during any particular growth stage of the crop. Optical remote sensing is very useful but, in cloudy days it becomes useless. Radar penetrates the cloud and collects information through the backscattering data. Normalized Difference Vegetation Index (NDVI) was extracted from Landsat 8 satellite data and used to calculate Crop Coefficient (Kc). The FAO-Penman-Monteith equation was used to calculate reference evapotranspiration (ETo). NDVI and Land Surface Temperature (LST) were calculated from satellite data and integrated with air temperature measurements to estimate Crop Water Stress Index (CWSI). Then, both CWSI and potential crop evapotranspiration (ETc) were used to calculate actual evapotranspiration (ETa). Sentinel-1 radar data were calibrated using SNAP software. The relation between backscattering (dB) and CWSI was an inverse relationship and R2 was as high as 0.82.
Highlights
With a rapidly growing world population, the pressure on limited fresh water resources increases
Water is an important component in agricultural production for both yield quantity and quality
Abutaleb 48 lenge of the agricultural sector is to produce more food from less water, which can be achieved by increasing Crop Water Productivity (CWP) [1]
Summary
With a rapidly growing world population, the pressure on limited fresh water resources increases. Remote sensing techniques were used and evaluated to estimate ETa and ETc [3]-[11] and predict soil water availability [12] for irrigation water management Factors such as water stress, stomata conductivity, heat flux, transpiration and cooling cause plants to close their stomata. One way to get an indicator for crop water stress is measuring plant water content; fresh biomass minus dry biomass. This is a very time consuming method, so it is not applicable to construct time series of crop water stress. The empirical relationship for canopy-air temperatures difference (Tc-Ta) versus Vapor Pressure Deficit (VPD) was represented to quantify the crop water stress. The main aim of this study is to estimate the crop water status through Radar and optical remote sensing data
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