Date of Award:

5-2026

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Plants, Soils, and Climate

Committee Chair(s)

Matt Yost

Committee

Matt Yost

Committee

J. Earl Creech

Committee

Grant Cardon

Abstract

In water limited environments, alfalfa is often criticized for its high water use, prompting implementation of new irrigation technologies, deficit irrigation, and adapted crop genetics. Cumulative potential benefits from combining, or stacking, these water-optimizing practices have not been identified. The objective of this on-farm research study was to determine how irrigation technologies, deficit irrigation, genetics, and combinations of these practices impact alfalfa yield and forage quality. Trials were conducted at three sites in Utah from 2020 to 2022 on young alfalfa stands (establishment and first one to three production years). Treatments included five irrigation technologies, four irrigation rates, and two alfalfa genetic strains. No interaction effects were found to be significant among these three factors. Main effects of technology, rate, and genetics varied by site-year. Three low-elevation irrigation application technologies typically outperformed the mid-elevation spray application and mobile drip irrigation, except for site-years without crop water stress in the presence of increased late-season precipitation. The 25% irrigation reduction typically performed similarly to the full irrigation rate. Conversely, two 50% reductions (constant vs. targeted reduction) were similar, indicating that targeting reduced irrigation did not improve yield or quality in alfalfa. Likewise, the drought-tolerant variety did not consistently outperform the growers’ conventional alfalfa. The lack of interactions in this study is evidence that there were no benefits from stacking these water-optimizing practices in one to three-year-old alfalfa. However, when used independently, growers may observe alfalfa yield and quality benefits from some of these water-optimizing practices.

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