Impact of water and nitrogen availability on maize evapotranspiration and soil water trends under high frequency sprinkler irrigation

Authors: King, Bradley - Brad; Tarkalson, David; Bjorneberg, David - Dave

Submitted to: Proceedings of the American Society of Agricultural and Biological Engineers International (ASABE)
Publication Type: Proceedings
Publication Acceptance Date: 6/1/2021
Publication Date: 7/10/2021
Citation: King, B.A., Tarkalson, D.D., Bjorneberg, D.L. 2021. Impact of water and nitrogen availability on maize evapotranspiration and soil water trends under high frequency sprinkler irrigation. Proceedings of the American Society of Agricultural and Biological Engineers International (ASABE) Virtual Meeting, July 12-16,2021. https://doi.org/10.13031/aim.202100639.
DOI: https://doi.org/10.13031/aim.202100639

Interpretive Summary: The dairy industry in southcentral Idaho has undergone rapid expansion in the region over the past 25 years transforming the common irrigated crop mix to include more forages to support the dairy feed consumption. Consequently, the acreage of alfalfa and maize, both for grain and forage, has increased. Historically, maize was a minor crop in the region and limited local information about water use is available. The relatively short maize growing season in the region prevents direct transfer of water use data from more humid longer growing season regions. The objectives of this study were to quantify and evaluate maize water use, grain yield, and soil water trends to multi-year nitrogen and irrigation deficits in southcentral Idaho. A secondary objective was to test the hypothesis that maize evapotranspiration (ETc) is independent of maize productivity in the region’s high evaporative demand environment under frequent irrigation required to achieve maximum yield. The effect of 0 and 246 kg ha-1 of nitrogen (N) application under fully irrigated (FIT) and three limited irrigation rates (75% FIT, 50% FIT, and 25 FIT) on maize yield and soil water trends were investigated in 2017, 2018 and 2019 under lateral-move irrigation in south central Idaho. Maize ET, grain yield and soil water contents were significantly different (p < 0.05) between irrigation treatments and study year. Grain yield decreased nonlinearly as seasonal irrigation amount decreased regardless of N supply. The maize ET and soil water contents from the two N rates within each irrigation level were the same. During each year of the study and within each irrigation treatment, there were no significant (p < 0.05) maize ET or soil water content differences between the N treatments. Assuming yields under different N application rates were representative of high and low maize productivity areas of a field, the results show that reducing water application to low productivity areas will reduce grain yield at the same rate as in high productivity areas. Thus, variable rate irrigation does not provide the opportunity to reduce water use and pumping costs while maintaining yield levels in low production areas.

Technical Abstract: One potential advantage of variable rate irrigation (VRI) is that less water can be applied to field areas with low productivity, without adversely affecting yield, thereby reducing water use, nutrient leaching, and pumping costs. This inferred potential advantage of VRI has not been fully evaluated experimentally. A three-year field study on maize (Zea mays L.) was conducted to test the hypothesis that high and low productivity has no effect on crop ET. High and low productivity were established using high and low soil N supplies. The effect of 0 and 246 kg ha-1 of nitrogen (N) application under fully irrigated (FIT) and three limited irrigation rates (75% FIT, 50% FIT, and 25 FIT) on maize yield and soil water trends were investigated in 2017, 2018 and 2019 under lateral-move irrigation in south central Idaho. Maize ET, grain yield and soil water contents were significantly different (p < 0.05) between irrigation treatments and study year. Grain yield decreased nonlinearly as seasonal irrigation amount decreased regardless of N supply. The maize ET and soil water contents from the two N rates within each irrigation level were the same. During each year of the study and within each irrigation treatment, there were no significant (p < 0.05) maize ET or soil water content differences between the N treatments. Assuming yields under different N application rates were representative of high and low maize productivity areas of a field, the results show that reducing water application to low productivity areas will reduce grain yield at the same rate as in high productivity areas. Thus, VRI does not provide the opportunity to reduce water use and pumping costs while maintaining yield levels in low production areas.