Date of Award:

8-2026

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Plants, Soils, and Climate

Committee Chair(s)

Matt A. Yost

Committee

Matt A. Yost

Committee

J. Earl Creech

Committee

J. Burdette Barker

Abstract

Water is becoming more limited in the western United States, including Utah, so farmers need forage crops that can produce well while using less irrigation water. This study examined how different forage crops respond to reduced irrigation and different irrigation application methods, and whether some crops can provide better economic returns under limited water conditions.

Field studies were conducted at three Utah locations, Cedar City, Logan, and Vernal, from 2020 to 2024. The alternative forage crops included teff, sorghum-sudangrass (sudex), and forage rye. For economic comparison, conventional forage crops included alfalfa, corn, and three-way small grains. Four to five irrigation application technologies were tested including three low elevation sprinklers, one mid elevation sprinkler, and mobile drip irrigation. Four irrigation levels were used: full irrigation, 75% of full irrigation, 50% of full irrigation, and a targeted 50% irrigation treatment.

Crop response depended on the crop, location, year, and amount of irrigation applied. Teff usually produced its greatest yield under full irrigation, while sudex often performed best under 75% irrigation. Lower irrigation levels often improved forage quality for teff and sudex. Forage rye generally had smaller changes in yield and quality across irrigation levels. Irrigation water productivity, which describes how much forage was produced per unit of irrigation water, was often greater under reduced irrigation than under full irrigation for all three forages, except few cases. Differences among irrigation technologies were less consistent, although mobile drip irrigation often produced lower biomass yield than sprinkler-based systems.

Economic results also varied by crop, location, and year. Corn and alfalfa more often produced positive and relatively stable profits per unit of land and per unit of irrigation water. However, teff and sudex performed better than conventional forage crops in some conditions, especially when corn was harvested as a grain. Overall, the results were evidence that no single crop or irrigation strategy was best in all situations. Instead, forage and irrigation decisions should be based on the producer’s goals, whether the priority is high yield, better forage quality, saving water, or improving economic return under limited irrigation.

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