Center pivot irrigation capacity effects on maize yield and profitability in the Texas High Plains

Authors: DOMINGUEZ, ALFONSO - University Of Castilla-La Mancha(UCLM); Schwartz, Robert; PARDO, JOSE - University Of Castilla-La Mancha(UCLM); GUERRERO, BRIDGET - West Texas A & M University; BELL, JOURDAN - Texas A&M Agrilife; Colaizzi, Paul; Baumhardt, Roland - Louis

Submitted to: Agricultural Water Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/5/2021
Publication Date: 11/19/2021
Citation: Dominguez, A., Schwartz, R.C., Pardo, J.J., Guerrero, B., Bell, J.M., Colaizzi, P.D., Baumhardt, R.L. 2021. Center pivot irrigation capacity effects on maize yield and profitability in the Texas High Plains. Agricultural Water Management. 261. Article 107335. https://doi.org/10.1016/j.agwat.2021.107335.
DOI: https://doi.org/10.1016/j.agwat.2021.107335

Interpretive Summary: In the Texas High Plains (THP), groundwater resources for irrigation are declining because of aquifer depletion. As a consequence, producers are often unable to meet peak water demands of corn. The constraints on irrigation capacity in the region reduces yield and profitability of corn production. Scientists from USDA ARS (Bushland, Texas), University of Castilla-La Mancha (Albacete, Spain), Texas A&M AgriLife, and West Texas A&M University simulated the influence of water allocation strategies for corn under center pivot irrigation on crop yield and net returns. Water allocations to a fraction of the pivot area were achieved by withholding irrigation from circular sectors or from outer spans. Unirrigated areas under the pivot were planted to dryland cotton or maintained in fallow. These strategies were evaluated for growing seasons with average and above average rainfall, and for years with a seasonal drought. Preseason irrigation had little influence on grain yield at irrigation capacities greater than 3.7 gallons per minute per acre (gpm). Slightly greater corn yields were simulated when a fraction of the pivot was irrigated for irrigation capacities less than 4.5 gpm under average rainfall. For irrigation capacities less than 5.9 gpm, reducing the irrigated area was the best option for optimizing net returns. Concentrating water generated greater net returns because of greater irrigation water productivities and lower seed and fertilizer costs. Compared with fallow, planting cotton in the unirrigated portion increased net returns except in years with a seasonal drought. Because greater irrigation did not always increase net returns, profitability can be increased and groundwater conserved by irrigating a fraction of the area when limited water is available for irrigation.

Technical Abstract: In the Texas High Plains (THP), groundwater resources for irrigation are declining because of aquifer depletion and reduced well capacities. Inability to meet peak water demands of maize under constrained irrigation capacities decreases yield and profitability. The MOPECO crop model, calibrated for the THP, was adapted to simulate maize water use and yield under center pivot irrigation to evaluate water allocation strategies under limited irrigation. Simulations were carried out over a range of irrigation capacities (3 – 12 mm d-1 for a 50.9 ha area), initial soil water contents, and application depths with irrigation allocated to a fraction (0.5 – 1.0) of the pivot area. Fractional water allocations were achieved by withholding irrigation from circular sectors or from outer spans with unirrigated fractions in fallow or planted to dryland cotton. These strategies were evaluated for growing seasons with average (TMY1), average to above average (TMY2), and below average (TMY3) precipitation. Preseason irrigation had little to no influence on grain yield at irrigation capacities = 5 mm d-1. At irrigation capacities =6 mm d-1 under average rainfall (TMY1), marginally greater yields 50.9 ha-1 were simulated when a fraction of the area was irrigated. For irrigation capacities =8 mm d-1 under TMY1, reducing the irrigated area was the most prudent option for optimizing net returns. As irrigation capacities increased from 4 to 8 mm d-1, the irrigated fraction that maximized net returns increased from 0.5 to 0.9. Concentrating water generated greater net returns because of greater irrigation water productivities and lower seed and fertilizer costs. Compared with fallow, planting cotton in the unirrigated portion increased net returns except in years with a seasonal drought (TMY3). Because greater irrigation volume did not always increase net returns, there is an opportunity to both increase profitability and conserve water by irrigating a fraction of the area.