Center Pivot Maintenance and Reduced Irrigation Impacts on Alfalfa Production

This manuscript has been accepted for publication in the  Agronomy Journal . The version of record is available at https://doi.org/10.1002/agj2.70366. © 2026 The American Society of Agronomy. This preprint is shared for non-commercial scholarly use.  Abstract: Growers in the Intermountain West of the United States require research-proven irrigation strategies to stretch limited water supplies amidst incessant droughts. Regular irrigation component maintenance and reduced irrigation rates can be beneficial. These strategies are untested in rigorous on-farm trials. This study evaluates an inexpensive and straightforward water management strategy to maintain crop yield and quality while reducing water use. Twelve on-farm alfalfa ( Medicago sativa L.) sites with center pivots in southcentral Utah were tested in the 2019-2020 growing seasons. Three treatments were evaluated: Old (existing irrigation equipment), New (new irrigation equipment), and New 90% (new irrigation equipment with 10% reduced irrigation rate). The treatments were applied to one center-pivot span at each site and replicated four times. Age of existing sprinkler equipment (pressure regulators and sprinkler heads/nozzles) ranged from 3 to over 20 years old. Nozzle and regulator wear ranged between 0% to 0.7% and -11% to 50%, respectively. Alfalfa yield and quality were evaluated on 63 cuttings from all twelve sites in the two growing seasons. Replacement of old irrigation equipment did not consistently improve alfalfa yield or quality, increasing yield in only 8% of 63 cuttings across both years. New 90% decreased yield in 11% of 63 cuttings across both years. Over both years, growers who bought New irrigation equipment could often lower irrigation rates by 10% without reducing alfalfa productivity. While Old sprinkler equipment may not cause as much alfalfa productivity loss as expected, maintenance is still required and is therefore recommended.