Abstract
Climate change will intensify water scarcity, and therefore irrigation must be adapted to save water. Operational tools that provide watering recommendations to end-users are needed. This work presents a new tool, Irrigation-Advisor (IA), which is based on weather forecasts and is able to separately determine soil evaporation and crop transpiration, and thus is adaptable to a broad range of agricultural situations. By calculating several statistical indicators, IA was tested against the FAO-56 crop evapotranspiration (ETcFAO) methodology using local crop coefficients. Additionally, IA recommendations were compared with current standard practices by experienced farmers (F). Six field experiments with four widely cultivated species (endive, lettuce, muskmelon and potato) were performed in Southeast Spain. Irrigation water applied, crop yield, aboveground biomass and water productivity were determined. Crop water needs underestimations (5%–20%) were detected when comparing IA against ETcFAO, although the index of agreement proved reasonable adjustments. The IA recommendations led to water savings up to 13% when compared to F, except for lettuce, with a 31% surplus in irrigation when using IA. Crop yield was not compromised and water productivity was increased by IA. Therefore, IA mimicked the farmers′ irrigation strategies fairly well without deploying sensors on-site. Nevertheless, improvements are needed for increasing the accuracy of IA estimations.
Highlights
Agriculture is the largest consumer of freshwater worldwide, accounting for 70% of water withdrawals, representing 2.7 Mhm3 annually used to irrigate 324 Mha (8300 m3 ha−1 ) [1]
In order to determine crop water requirements, most farmers and irrigation-advising websites have often used the one-layer methodology proposed by Allen et al [6], Food and Agriculture Organization of the United Nations (FAO) Irrigation and Drainage paper No 56 (FAO-56), which is based on the multiplication of the reference evapotranspiration (ETo ), calculated with the Penman–Monteith approach, by a crop coefficient (Kc ) that represents the relative rate of evapotranspiration by a specific crop (ETc )
The one-layer methodology considers the crop as a single big leaf and cases with partial vegetation cover, such as vegetable crops, might not satisfy completely such a hypothesis [11]; this could be solved by applying the dual-Kc approach that has been developed under FAO-56 [6]
Summary
Agriculture is the largest consumer of freshwater worldwide, accounting for 70% of water withdrawals, representing 2.7 Mhm annually used to irrigate 324 Mha (8300 m3 ha−1 ) [1]. In order to determine crop water requirements, most farmers and irrigation-advising websites have often used the one-layer methodology proposed by Allen et al [6], Food and Agriculture Organization of the United Nations (FAO) Irrigation and Drainage paper No 56 (FAO-56), which is based on the multiplication of the reference evapotranspiration (ETo ), calculated with the Penman–Monteith approach, by a crop coefficient (Kc ) that represents the relative rate of evapotranspiration by a specific crop (ETc ) This method can be considered as a reference due to its extensive use and reliable results, as reported for a great number of crops [7,8,9]. Discrepancies exist between the actual crop characteristics (percentage of ground cover, crop height, phenological stage, etc.) and the published
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