Matteo Ippolito, Dario De Caro, Giuseppe Ciraolo, Mario Minacapilli, Giuseppe Provenzano
{"title":"Estimating crop coefficients and actual evapotranspiration in citrus orchards with sporadic cover weeds based on ground and remote sensing data.","authors":"Matteo Ippolito, Dario De Caro, Giuseppe Ciraolo, Mario Minacapilli, Giuseppe Provenzano","doi":"10.1007/s00271-022-00829-4","DOIUrl":null,"url":null,"abstract":"<p><p>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 K<sub>c</sub> 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 K<sub>c</sub> 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 K<sub>c</sub>(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 K<sub>c</sub> 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 (ET<sub>a</sub>) 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 ET<sub>a</sub> were characterized by root-mean-square-error, RMSE, and mean bias-error, MBE, of 0.48 and -0.13 mm d<sup>-1</sup> respectively, while the estimated soil water contents, SWC, were characterized by RMSE equal to 0.01 cm<sup>3</sup> cm<sup>-3</sup> 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.</p>","PeriodicalId":14650,"journal":{"name":"Irrigation Science","volume":"41 1","pages":"5-22"},"PeriodicalIF":3.1000,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9898492/pdf/","citationCount":"4","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Irrigation Science","FirstCategoryId":"97","ListUrlMain":"https://doi.org/10.1007/s00271-022-00829-4","RegionNum":2,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"AGRONOMY","Score":null,"Total":0}
引用次数: 4
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.
期刊介绍:
Irrigation Science publishes original contributions and short communications reporting the results of irrigation related research, including relevant contributions from the plant, soil and atmospheric sciences and the analysis of field experimentation as well as irrigation water management modeling. Special emphasis is on multi-disciplinary studies dealing with the problems involved in maintaining the long term productivity of irrigated lands and in increasing the efficiency of agricultural water use.
Aspects of particular interest are: physiology of plant growth and yield response to water status; physical and chemical aspects of water status and movement in the plant-soil-atmosphere system; salinity and alkalinity control by soil and water management; agricultural drainage, measurement and modification of crop and control of water in plant, soil and atmosphere; water requirements in irrigation practice; irrigation scheduling and ecological aspects of irrigated agriculture.