Mapping within‑field variability of soybean evapotranspiration and crop coefficient using the Earth Engine Evaporation Flux (EEFlux) application

Abstract

Accurate information about the spatiotemporal variability of actual crop evapotranspiration (ETa), crop coefficient (K c) and water productivity (WP) is crucial for water efficient management in the agriculture. The Earth Engine Evapotranspiration Flux (EEFlux) application has become a popular approach for providing spatiotemporal information on ETa and Kc worldwide. The aim of this study was to quantify the variability of water consumption (ETa) and the K c for an irrigated commercial planting of soybeans based on the EEFlux application in the western region of the state of Bahia, Brazil. The water productivity (WP) for the fields was also obtained. Six cloud-free images from Landsat 7 and 8 satellites, acquired during the 2016/17 soybean growing season were used and processed on the EEFlux platform. The ETa from EEFlux was compared to that of the modified FAO (MFAO) approach using the following statistical metrics: Willmot's index of agreement (d-index), root mean square error (RMSE), mean absolute error (MAE) and mean bias error (MBE). The K c from EEFlux was compared to the K c used in the soybean field (K c FAO-based) and to the K c values obtained in different scientific studies using the d-index. A similar procedure was performed for WP. Our results reveal that EEFlux is able to provide accurate information about the variability of ETa and the K c of soybean fields. The comparison between ETa EEFlux and ETa MFAO showed good agreement based on the d-index, with values of 0.85, 0.83 and 0.89 for central pivots 1, 2 and 3, respectively. However, EEFlux tends to slightly underestimate ETa. The K c EEFlux showed good accordance with the K c values considered in this study, except in phase II, where a larger difference was observed; the average WP of the three fields (1.14 kg m-3) was higher than that in the majority of the previous studies, which is a strong indicator of the efficient use of water in the studied soybean fields. The study showed that EEFlux, an innovative and free tool for access spatiotemporal variability of ETa and Kc at global scale is very efficient to estimate the ETa and Kc on different growth stages of soybean crop.

Analysis of the groundwater scenario with respect to the crop water productivity for the Betwa–Dhasan river basin, Bundelkhand using remote sensing techniques

“…The evaporative fraction (K) parameter used in this model almost remains constant throughout the day, so it is feasible to use the value of instantaneous ET as daily ET (Li et al 2008). For eDcient water management in agriculture, precise information about the spatio-temporal variation of AET is crucial (Venancio et al 2020). The information about ET, along with yield, is required for the analysis of the CWP.…”

“…CWP has been deBned as the measurement of the eDciency of water use. The unit for this parameter is kg/m 3 or kg/(ha-mm) (Li et al 2008;Venancio et al 2020). Climatic parameters also aAect the ET.…”

Achieving Breakthroughs in Global Hydrologic Science by Unlocking the Power of Multisensor, Multidisciplinary Earth Observations

“…(2016) mapped global surface extent and trends, and Venancio et al. (2020) mapped evapotranspiration at field spatial scales. Bair et al.…”

Assessing Spatio-Temporal Dynamics of Deep Percolation Using Crop Evapotranspiration Derived from Earth Observations through Google Earth Engine

“…Vegetation indices such as NDVI can be extracted from satellite images on the platform, and they can be viewed in time series charts or transferred to external processing. GEE was successfully used to estimate crop evapotranspiration [34][35][36], crop productivity [37,38], to cartograph crop areas [39][40][41], for supporting irrigation scheduling [42,43], and water management [44].…”