Date of Award:

5-2023

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Plants, Soils, and Climate

Committee Chair(s)

Matt Yost

Committee

Matt Yost

Committee

J. Earl Creech

Committee

Burdette Barker

Committee

Grant Cardon

Committee

Alfonso Torres

Abstract

Irrigation is critical to meeting global food and fiber demands. Optimizing agricultural irrigation may help sustain production levels, while reducing its demand for water. This research evaluated precision sprinklers and drip irrigation for pivots, five pivot track mitigation tools, three scientific irrigation scheduling (SIS) methods, sensors for surface irrigation cutoff, and automating surface systems to implement surge irrigation. With pivots and surface irrigation being the most common methods for irrigation in the West, small improvements from these tools could result in significant water savings.

Low energy precision application (LEPA) sprinklers and mobile drip irrigation (MDI) were tested on two pivots. LEPA did not often maintain yield, even with similar application amounts to the mid elevation sprinkler application (MESA) control. MDI reduced yield by 6 – 25% in 2018, while applying half as much water as MESA. In following years, MDI rarely maintained yield, even when applying more than MESA. For LEPA and MDI to maintain yield with less water, the correct situations and proper adaptations must be carefully chosen.

With the intent to improve pivot wheel tracks, installing LEPA around the pivot tower was the best of five tested methods, reducing track depths by 47 – 63% in one year. Adapting the correct method to field conditions and position on the pivot can result in shallower wheel tracks without sacrificing yield.

The use of soil moisture sensors, a commercial irrigation scheduler, and a free irrigation scheduler to determine irrigation amounts, were compared with the rates chosen by farmers. At some farms, the SIS methods maintained yield with 10-15% less irrigation. These benefits were usually when precipitation was high, which the SIS methods accounted for well.

Surface irrigators found that sensors helped reduce irrigation application by correctly timing the cutoff, saving them time, water, and money. Automation to implement surge irrigation increased irrigation use efficiency by 43% the first year, but had less drastic results in the final year, likely due to the severity of an ongoing drought. These collective results demonstrate that simple water optimization techniques could reduce irrigation diversions by 15 and possibly up to 25% or more in some cases.

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