Estimation of dwarf green bean water use under semi-arid climate conditions through ground-based remote sensing techniques |
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Authors: | Eyü p Selim Kö ksal,Sü leyman Kodal,Yusuf Ersoy Yildirim |
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Abstract: | Determination of temporal and spatial distribution of water use (WU) within agricultural land is critical for irrigation management and could be achieved by remotely sensed data. The aim of this study was to estimate WU of dwarf green beans under excessive and limited irrigation water application conditions through indicators based on remotely sensed data. For this purpose, field experiments were conducted comprising of six different irrigation water levels. Soil water content, climatic parameters, canopy temperature and spectral reflectance were all monitored. Reference evapotranspiration (ET0), crop coefficient Kc and potential crop evapotraspiration (ETc) were calculated by means of methods described in FAO-56. In addition, WU values were determined by using soil water balance residual and various indexes were calculated. Water use fraction (WUF), which represents both excessive and limited irrigation applications, was defined through WU, ET0 and Kc. Based on the relationships between WUF and remotely sensed indexes, WU of each irrigation treatments were then estimated. According to comparisons between estimated and measured WU, in general crop water stress index (CWSI) can be offered for monitoring of irrigated land. At the same time, under water stress, correlation between measured WU and estimated WU based on CWSI was the highest too. However, canopy-air temperature difference (Tc − Ta) is more reliable than others for excessive water use conditions. Where there is no data related to canopy temperature, some of spectral vegetation indexes could be preferable in the estimation of WU. |
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Keywords: | CWSI, crop water stress index DAP, day after planting ET, evapotranspiration ET0, reference evapotranspiration ETc, crop evapotranspiration Kc, crop coefficient LAI, leaf area index NIR, near infrared RH, relative humidity SAVI, soil adjusted vegetation index SR, simple ratio SWC, soil water content Ta, air temperature TAM, total available moisture Tc, crop canopy temperature Tc &minus Ta, crop canopy-air temperature difference VPD, vapour pressure deficit WI, water index WU, water use WUF, water use fraction |
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