Estimating crop coefficients and actual evapotranspiration in citrus orchards with sporadic cover weeds based on ground and remote sensing data

Abstract

Accurate estimations of actual crop evapotranspiration are of utmost importance to evaluate crop water requirements and to optimize water use efficiency. At this aim, coupling simple agro-hydrological models, such as the well-known FAO-56 model, with remote observations of the land surface could represent an easy-to-use tool to identify biophysical parameters of vegetation, such as the crop coefficient Kc under the actual field conditions and to estimate actual crop evapotranspiration. This paper intends, therefore, to propose an operational procedure to evaluate the spatio-temporal variability of Kc in a citrus orchard characterized by the sporadic presence of ground weeds, based on micro-meteorological measurements collected on-ground and vegetation indices (VIs) retrieved by the Sentinel-2 sensors. A non-linear Kc(VIs) relationship was identified after assuming that the sum of two VIs, such as the normalized difference vegetation index, NDVI, and the normalized difference water index, NDWI, is suitable to represent the spatio-temporal dynamics of the investigated environment, characterized by sparse vegetation and the sporadic presence of spontaneous but transpiring soil weeds, typical of winter seasons and/or periods following events wetting the soil surface. The Kc values obtained in each cell of the Sentinel-2 grid (10 m) were then used as input of the spatially distributed FAO-56 model to estimate the variability of actual evapotranspiration (ETa) and the other terms of water balance. The performance of the proposed procedure was finally evaluated by comparing the estimated average soil water content and actual crop evapotranspiration with the corresponding ones measured on-ground. The application of the FAO-56 model indicated that the estimated ETa were characterized by root-mean-square-error, RMSE, and mean bias-error, MBE, of 0.48 and -0.13 mm d−1 respectively, while the estimated soil water contents, SWC, were characterized by RMSE equal to 0.01 cm3 cm−3 and the absence of bias, then confirming that the suggested procedure can produce highly accurate results in terms of dynamics of soil water content and actual crop evapotranspiration under the investigated field conditions.

Irrigation optimization enhances water management and tree performance in commercial citrus groves on sandy soil.

“…[1%] is the permanent wilting point (Morgan et al 2006;Ippolito et al 2022). The irrigation rates in the current experiment had two different rates for the 360 and 485 trees ha − 1 (78%-ET c , and 100%-ET c ), and the 920 trees ha − 1 irrigation rates (50%-ETc, 78%-ET c , and 100%-ET c ) corresponding to 31.4 L h − 1 , 48.5 L h − 1 , and 62.8 L h − 1 for 50%-ET c (de cit) 78%-ET c (moderate), and 100%-ET c (high /grower standard) emitters, respectively.…”

Irrigation challenges in the COVID-19 scenario

“…1. Estimating crop coefficients and actual evapotranspiration in citrus orchards with sporadic cover weeds based on ground and remote sensing data (Ippolito et al 2022) 2. Irrigation efficiency optimization at multiple stakeholders' levels based on remote sensing data and energy water balance modelling (Corbari and Mancini 2022).…”

“…Thus, it is a need to better estimate crop water requirements. Ippolito et al (2022) suggest a procedure to obtain highly accurate results on dynamics of soil water content and actual crop evapotranspiration under the investigated field conditions. Moreover, it highlights that site-specific crop coefficients, accounting for local and time-variable conditions in the field, can improve crop water requirement predictions, irrigation scheduling and thus, can also forward the implementation of precision irrigation strategies.…”

Setting Irrigation Thresholds for Building a Platform Aimed at the Improved Management of Citrus Orchards in Coastal Syria

“…Numerous applications of the A&P approach to tree crops have been reported, e.g., by Paço et al [23] for peach; Paço et al [24] and Puig-Sirera et al [25] for olive; Vinci et al [26] for hazelnut; and Mobe et al [27] for various apple orchards in South Africa. Applications to vineyards include Williams et al [21], who reported on a survey of California vineyards, using A&P. The applications to citrus are also numerous [28][29][30][31][32]. These applications make us confident about the effectiveness of using the A&P approach.…”