Estimating Evapotranspiration of an Apple Orchard Using a Remote Sensing-Based Soil Water Balance

Abstract

Abstract:The main goal of this research was to estimate the actual evapotranspiration (ET c ) of a drip-irrigated apple orchard located in the semi-arid region of Talca Valley (Chile) using a remote sensing-based soil water balance model. The methodology to estimate ET c is a modified version of the Food and Agriculture Organization of the United Nations (FAO) dual crop coefficient approach, in which the basal crop coefficient (K cb ) was derived from the soil adjusted vegetation index (SAVI) calculated from satellite images and incorporated into a daily soil water balance in the root zone. A linear relationship between the K cb and SAVI was developed for the apple orchard K cb = 1.82¨SAVI´0.07 (R 2 = 0.95). The methodology was applied during two growing seasons (2010-2011 and 2012-2013), and ET c was evaluated using latent heat fluxes (LE) from an eddy covariance system. The results indicate that the remote sensing-based soil water balance estimated ET c reasonably well over two growing seasons. The root mean square error (RMSE) between the measured and simulated ET c values during 2010-2011 and 2012-2013 were, respectively, 0.78 and 0.74 mm¨day´1, which mean a relative error of 25%. The index of agreement (d) values were, respectively, 0.73 and 0.90. In addition, the weekly ET c showed better agreement. The proposed methodology could be considered as a useful tool for scheduling irrigation and driving the estimation of water requirements over large areas for apple orchards.

Irrigation Performance Assessment in Table Grape Using the Reflectance-Based Crop Coefficient

“…Melton et al [27] proposed the use of a generalized relationship for real-time and operational purposes that enables its applications to crop-specific relationships a posteriori when information about crop architecture is available. In agreement with this line of thinking, several authors [17,28,29] concluded that some relationships developed for different crops are valid for the assessment of ETc in different crops and areas. Therefore, the relationship used in this work was the Kcb-NDVI relationship developed by Campos et al [13] in an irrigated vineyard managed in vertical shoot-positioned trellises (Equation (3)) in the West of Spain (semi-arid area).…”

“…The differences in the maximum values of NDVI or Kcb obtained in the different experiments, as well as the multiannual variability described in this work, reinforce the necessity of feasible approaches based on field data to describe the actual crop coefficient (in situ) and the water requirements for the crop analyzed. In the same vein, the proposed approach could provide valuable information for the assessment of irrigation necessities as proposed in previous experiments [10,17,29]. In addition, the availability of satellite images and the accessibility of using the most recent developments [14] allow operative applications, as presented in this study.…”

“…Hornbuckle et al [28] concluded that this relationship reproduces the Kcb behavior for wine-grapes in Australia. Finally, Odi-Lara et al [17] concluded that the relationship between the Kcb and the soil adjusted vegetation index for apple trees in the south of Chile was very similar to the relationship described by Campos et al [13] using the same index. While the Kcb-NDVI relationship should be evaluated in more canopies and climate conditions, the evidence provided let us use the proposed relationship for real-time and operational purposes.…”

“…However, applying these methods to fruit trees is of paramount importance [12,13] because the differences in local practices (planting densities, plant architecture, and the management of the crop understory) have a great effect on the actual value of the crop coefficient [14]. Successful evaluations of the estimated ETc using the Kc-VI relationship have been determined for pecan trees [15], vineyards [12,16], and apples [17]. Some of these authors already postulated the desirable use of these approaches for irrigation assessment in operative scenarios.…”

Assessment of actual evapotranspiration over a semi-arid heterogeneous land surface by means of coupled low resolution remote sensing data with energy balance model: comparison to extra Large Aperture Scintillometer measurements

“…Hence, to improve its estimation a reduction factor proposed by Torres and Calera (2010) was applied to deal with this problem in several studies (e.g. Odi-Lara et al, 2016;Saadi et al, 2015). Furthermore, since actual ET is computed based on actual soil 105 moisture status, the limited knowledge of the actual farmers' irrigation scheduling is a further critical limitation for SWB modeling.…”