Non Technical Summary
Throughout the Western U.S., irrigation is necessary for production of most crops. Many small and medium-sized farms in the West are irrigated using wheel-line (wheel-move or side-roll) systems that are more labor-intensive than systems common on larger farms. Many contemporary wheel-line systems are similar to those used half a century ago. The long-term goal of the proposed research is to identify and quantify cost and resource optimization opportunities for wheel-line irrigation to benefit small and medium-sized farms. This will be done by investigating the benefits and costs of modernizing wheel-line systems with lower pressure (lower energy requirement) sprinkler technologies; remote-controlled, solar-powered system movers; and automated system shutoff. The study will include a combination of surveys, field research, and subsequent economic analyses. Current and potential users of solar-powered remote-controlled wheel-lines will be surveyed. Field research will include performance testing of conventional and modern sprinkler technologies, field studies to determine yield impacts of the sprinkler technologies, and documentation of labor benefits of modern system movers and automated shutoff valves.The investigators hypothesize that the modernization will improve profit, decrease labor requirements, decrease carbon emissions, and increase crop water use efficiency for an overall net monetary and environmental benefit. This will directly improve the sustainability of small and medium-sized farms that rely upon wheel-line irrigation and the communities that rely upon these farms. Therefore, the proposed research is directly relevant to the Agricultural and Food Research Initiative Agricultural Economics and Rural Communities Priority Area and the Small and Medium-Sized Farms Subpriority Area.

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
601	6030	3010	20%
405	0210	2020	21%
111	0210	2020	39%
205	1640	3100	20%

Knowledge Area
601 - Economics of Agricultural Production and Farm Management; 111 - Conservation and Efficient Use of Water; 205 - Plant Management Systems; 405 - Drainage and Irrigation Systems and Facilities;

Subject Of Investigation
1640 - Alfalfa; 0210 - Water resources; 6030 - The farm as an enterprise;

Field Of Science
2020 - Engineering; 3010 - Economics; 3100 - Management;

Goals / Objectives
Objectives1) Identify the most economical (both monetary and resource) sprinkler selection for wheel-line irrigation systems in the Intermountain West climate.2) Identify the most economical (both monetary and resource) level of wheel-line system automation from presently available options.TimelineThe proposed project will be completed over a nearly four-year period from September 2023 to May 2027. Research will begin with the hiring of an MS student focusing on agronomy. The surveys will be conducted in the fall of 2023 with results being available to inform the field studies, which will begin in 2024 and continue through the 2026 growing season. A PhD student will be hired in January 2024. This individual will be heavily involved in the sprinkler testing and field studies. Data analysis will be continuous throughout the experiment as much as is reasonably possible. Output will include refereed journal manuscripts and Extension factsheets submitted as early as mid-2024 and continuing until the final manuscripts, which will correspond to the MS student focusing on economics finishing their program in the spring of 2027. The proposed schedule will enable three full irrigation seasons for the field experiments.

Project Methods
Project ActivitiesThe research will include the following activities:1) Two grower surveys will be conducted to identify the willingness to accept, and challenges to accepting solar-powered, remote-controlled wheel-line movers. One survey will be sent to current users of solar-powered wheel-line movers in the Intermountain West. The second survey will be sent to a broader group of Utah growers (~2,000) asking about interest in solar-powered irrigation systems. These surveys will provide valuable information into the sociological aspects of wheel-line modernization and provide valuable input into the experiment in terms of needs assessments. Co-PI Yost will lead this effort and draft surveys have been developed.2) Performance testing of commonly used brass impact sprinklers and modern alternatives. This includes sprinkler throw and distribution measurements at expected operating pressures through catch can studies (Figure 8) This will enable an objective, third-party comparison of sprinkle performance to assess the suitability of sprinkler alternatives for existing wheel-line systems and any recommendations on wheel-line set location spacing modifications for new systems. This activity will be led by PI Barker.3) Conduct two three-year field studies at USU research farms comparing yield, irrigation uniformity, irrigation wind and evaporation losses, and net applied irrigation for appropriate modern sprinkler designs and brass impact sprinklers. The farm in North Logan, UT (Greenville Farm) and the farm in Kaysville, UT would be used (Figure 10). One system at each farm will also equipped with an automated shutoff valve so that labor requirements can be directly compared to conventional wheel-lines at the same farms throughout two growing seasons (Figure 9). If additional funds can be secured through USU, one wheel-line at each of these farms will also be equipped with a remote-controlled mover. The crops irrigated will include alfalfa and/or small grains depending on rotations at the respective farms during the experiment.4) Four cooperative field studies will also be performed in four different Utah Counties:a) Cache County, which is within the Great Salt Lake watershed;b) Iron County, in Southern Utah, which has different precipitation patterns than northern Utah and heavy reliance on groundwater;c, d) Duchesne and Uintah Counties, which are in the Upper Colorado River Basin and also have a significant amount of land in the Uintah and Ouray Indian Reservation.5) A comprehensive economic study will be performed by Co-PI Larsen incorporating the water use, crop yield, and labor use data collected in the field experiments. This study will include energy costs, carbon footprint of irrigation pumping and system movement. It will also include any costs associated with modernization, including pumping station modifications. The costs and benefits of changing irrigation set timing and frequency, including for crop germination or recovery after hay cutting. Any relevant opportunity costs will also be considered.The techniques for the five primary project activities are described below:1) Surveys: Per Federal law, the draft surveys have been approved by the USU Institutional Review Board for testing involving human subjects.2) The sprinkler performance testing will follow ASAE Standard S398.1 maintained by the American Society of Agricultural and Biological Engineers.3) The field research studies will include appropriate statistical design, including randomization and replication at each site. Irrigation uniformity evaluations will follow commonly accepted methods (e.g., those of Merriam and Keller, 1978) with additional measurements of sprinkler flow, which has been adopted by PI Barker for a more comprehensive assessment of wheel-lines as part of Extension work in Utah. It is likely only feasible to perform these evaluations one to three times per growing season. Evaporation losses will be measured using individual sprinkler discharge measurements and catch-can measurements several times each growing season.4) Similar methods will be used for the cooperator fields. However, uniformity and evaporation losses will only be measured once per growing season and yield sampling may be reduced to only three locations per plot.5) The economic analysis will follow approved methods, including estimating costs and returns that will be incorporated into a farm-level enterprise budgets for different study areas. The enterprise budgets will provide the information required to do a partial budget analysis of adopting new irrigation technology.Data Analysis and InterpretationData will be analyzed according to the aforementioned standards and procedures. Statistical analyses will include appropriate analyses of variance (ANOVAs) using linear mixed models. The data will be interpreted considering economic, engineering, and agronomic meaningful differences in addition to statistical analyses.