Center Pivot Irrigation Management Optimization of Dry Beans in Humid Areas

During the spring growing season, periods of drought can cause a significant reduction in dry bean yield inBrazil. Therefore, irrigation is applied to reduce the risks associated with the variability in weather conditions. Thecommon irrigation system in Brazil is a center pivot system. Irrigation managers usually operate a center pivot irrigationsystem in such a way that it requires more than one day to complete the irrigation of an entire field. In general, cropmodel simulations assume that irrigation of an entire field is completed in one day. This article presents modificationmade in the CROPGRO simulation model to provide irrigation managers with decision support information that isequivalent to their local conditions. The modified model takes into account the number of days that a center pivotirrigation system requires to complete one revolution. Different management regimes for three different water capacitycenter pivot systems were evaluated for dry bean as a function of net return for the State of Parana, Brazil. Themanagement regimes that were evaluated included the completion of the center pivot revolution in either one, two or threedays. Six different irrigation thresholds were applied, ranging from 40 to 90% of the remaining available soil watercontent, and three different commodity prices were analyzed. The center pivot system that showed the highest net returnwas the system that applied 6 mm/day. The irrigation management regime that resulted in the highest net return was toirrigate the entire field in one day (the highest frequency possible), when the soil water content in the top 30 cm of theprofile dropped below 70 or 80% of available soil water, depending on the commodity price. Future research is needed toevaluate different weather conditions and soil types to make these modifications in the CROPGRO simulation model morewidely applicable.