Date of Award:

5-2022

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

Niel Allen

Committee

Jessica Ulrich-Schad

Abstract

The concept of 4R (right source, rate, placement, and timing) management needs little introduction due to the surplus of nutrient studies in the literature for most cultivated crops. However, few studies have looked at these practices in the Intermountain West with nitrogen use, and fewer looked at 4R irrigation management. A survey was conducted to explore the interactions of nitrogen and irrigation management, test sensitivity to supply and price changes of nitrogen and irrigation for Utah and Idaho growers of small grains, corn, and potatoes, and determine the current adoption of precision agriculture options and identify the opportunities to improve. A grower management online survey was emailed to 5,000 Utah and Idaho growers in early 2020. Questions were asked about farm demographics, 4R nitrogen and irrigation management, and precision agriculture usage. Though a low response rate, the 146 responses represented 25,000 hectares of crop production. Limited significant interactions occurred for the independent and dependent variables. Responses suggested that growers in the two states are willing to change as they are not completely satisfied with their management practices. There were implications of the need to change and continue fine tuning recommendations and building trust with growers.

Water has always been a limiting factor in crop production in the Intermountain West, but recent pressure to urbanization, unstable global markets, and changing climate has exacerbated the problem. Ways to optimize water have been tested individually, but not in a stacking environment with their effects on yield and quality of silage corn (Zea mays L.). The field study objectives were to evaluate the impact of soil management, crop genetics, irrigation technology, and irrigation rate on corn for silage yield and quality. Logan, Vernal, and Cedar City, Utah were used to generate five site-years of data from 2019 to 2021 on irrigation technology, rates, and management factors. Silage corn yield and quality were collected and analyzed as a nested factorial randomized block design. Analysis across factors and site years suggested that stacking of higher magnitudes results in less significant yield and quality benefits or losses. Rate reductions resulted in the highest yield losses, but reductions also maintained quality.

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