Date of Award:

5-2024

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Plants, Soils, and Climate

Committee Chair(s)

Matt A. Yost

Committee

Matt A. Yost

Committee

Burdette Barker

Committee

Grant Cardon

Committee

Bryan Hopkins

Committee

Scott Jones

Abstract

Proper irrigation and nutrient management are vital for optimal crop production within agricultural fields. Improving irrigation and nutrient application through precision agriculture is necessary to conserve the limited resources available, while improving yield and quality of crops produced through such a system. Variable rate irrigation (VRI) and variable rate nitrogen are systems used to apply water and nitrogen more precisely to agricultural fields to reduce runoff, deep percolation, leaching, and other negative impacts of over application, while providing the optimal rates to produce maximum yields. However, the processes to utilize these systems have proven to be more difficult than expected, and the technology has developed at a faster rate than the knowledge to manage such systems. Much research has been performed to determine different ways to use VRI and VRN, but many studies have been more technical than application based.

This research has focused on farm-scale trials to assist in further exploration of managing VRI and VRN in three ways. First, determine sensor placements based on resources available to the farmer to assist in making in-season irrigation decisions. Second, utilize satellite imagery to estimate in-season variation of soil moisture throughout fields that could assist with irrigation management. Third, trial a zone delineation and management plan for VRN that utilizes resources readily available to growers.

These analyses found that farmer's experience combined with yield maps are reliable tools for placing soil moisture sensors that capture soil VWC variability for precision irrigation. Utilizing satellite imagery with some vegetative indices were useful in estimating soil moisture throughout a field, and exploring some soil indices could prove useful in estimating soil moisture at different crop growth stages. These studies also found that sectioning a field into high and low yield productivity areas and applying different rates of N based on those productivity areas resulted in higher crop yields and improved nitrogen use efficiency. Overall, these results show the benefit of utilizing resources readily accessible to the farmer, as well as the experience of the farmer to implement VRI and VRN systems to improve crop production as well as conservation in resources.

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