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Determination of the FAO-56 Crop Coefficients for Peanut under Deficit Irrigation in a Humid Climate

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  2007 ASAE Annual Meeting  072154.(doi:10.13031/2013.23415)
Authors:   Ayman A Suleiman, Cecilia M Tojo Soler, Gerrit Hoogenboom
Keywords:   Irrigation efficiency, Irrigation scheduling, Penman-Monteith, Southeastern USA

There is a lack of information about crop coefficients to be used with the FAO-56 reference evapotranspiration (ETo) approach for peanut grown in humid climates in general and under deficit irrigation in particular. The objective of this study was to determine the crop coefficients for peanut under different deficit drip irrigation treatments for a humid climate. Peanut was grown in 2006 in three automated rainout shelters located at the University of Georgia Campus in Griffin, Georgia, USA. The irrigation treatments were 40%, 60% and 90% irrigation thresholds (IT). The least irrigated treatment corresponded to the 40% IT and the most irrigated was the 90% IT. When the modeled soil water content in the effective root zone dropped below a specific threshold of the available water content (AWC), irrigation was applied until the soil water reached 100% of AWC. The length of the initial stage was similar for the different treatments, while 40% IT had longer development and mid-season stages and shorter late stage than the other two treatments. The length of the development, mid-season, and late stages were close for the 60 and 90% IT. Deficit irrigation had a pronounced impact on the crop coefficient values, especially for the mid-season stage. The crop coefficient values for the 90% IT may be used in humid climates to calculate the peanut water requirements under full irrigation. The use of the appropriate crop coefficient values along with the appropriate length of the development stages will result in more efficient irrigation scheduling and water use planning in humid climates.

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