Evaluating uniformity of center pivot irrigation systems in western Oklahoma

Authors: MASASI, BLESSING - Oklahoma State University; HANDA, DIVYA - Iowa State University; FRAZIER, ROBERT - Oklahoma State University; TAGHVAEIAN, SALEH - Oklahoma State University; WARREN, JASON - Oklahoma State University; Moriasi, Daniel

Submitted to: Applied Engineering in Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/19/2022
Publication Date: 4/10/2022
Citation: Masasi, B., Handa, D., Frazier, R.S., Taghvaeian, S., Warren, J.S., Moriasi, D.N. 2022. Evaluating uniformity of center pivot irrigation systems in western Oklahoma. Applied Engineering in Agriculture. 38(2):313-319. https://doi.org/10.13031/aea.14626.
DOI: https://doi.org/10.13031/aea.14626

Interpretive Summary: Improvement of the performance of irrigation systems is critical to addressing declining groundwater resources and ensuring environmental integrity in Oklahoma. In this study, we conducted irrigation audits to investigate the application uniformity and conveyance efficiency of center pivots in western Oklahoma. The results showed wide ranges of irrigation uniformities and conveyance efficiencies for the tested center pivots. About one-third of the tested center pivots performed below acceptable levels of irrigation uniformity. The average conveyance efficiency for the tested systems was less than 100%, which indicates existence of water losses. Water losses were mainly caused by pipe leakages on the systems and wind drift. Results based on the irrigation audits data revealed that irrigation nonuniformities caused large deep percolation fluxes and nutrient losses in areas that were over irrigated, which can lead to contamination of downstream water resources. Furthermore, irrigation nonuniformities had negative impacts on crop yield. These results highlight the need for improving irrigation uniformity of center pivots in western Oklahoma. In addition, these results will likely motivate producers to improve performance of their irrigation systems in order to conserve the limited water resources and reduce their pumping energy costs.

Technical Abstract: Nonuniform application of water through center pivots can lead to under- or over-irrigation at parts of the field, which can lead to water stress and yield reductions or loss of limited water resources and leaching of applied chemicals. In this study, irrigation uniformity tests were carried out to determine the application uniformity and conveyance efficiency of 21 center pivots in western Oklahoma. The average coefficient of uniformity and lower quarter distribution uniformity of the tested systems were 80 and 71%, respectively, indicating an overall borderline acceptable application uniformity. The average water conveyance efficiency was 94%, suggesting that 6% of pumped water was lost before reaching the soil surface. Based on the results of the irrigation audits, the DAYCENT ecosystem model was used to simulate the environmental impacts of irrigation nonuniformities for a typical corn field in the Oklahoma Panhandle. Full irrigation (FI) treatment representing uniform application and under irrigation (UI) and over irrigation (OI) treatments representing average observed nonuniformities were simulated over three growing seasons. The average seasonal deep percolation fluxes were 55, 37, and 240 mm under the FI, UI and OI treatments, respectively. This resulted in leaching of 2.8, 1.9, and 4.9 kg ha-1 of organic nitrogen from the same treatments, respectively. In addition, nitrate concentrations in the top 1.5 m of the soil were considerably smaller under OI treatment. Emission of carbon dioxide and nitrous oxide, which are greenhouse gases, was larger under FI and OI compared to UI treatment. Lastly, the amounts of carbon and nitrogen in grain were 23 and 16% smaller for the UI and OI than the FI treatment, respectively.