Simulated irrigation water productivity and related profit effects in U.S. Southern High Plains cotton production

Authors: Mauget, Steven; Ulloa, Mauricio; MITCHELL-MCCALLISTER, DONNA - Texas Tech University

Submitted to: Agricultural Water Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/28/2022
Publication Date: 3/15/2022
Citation: Mauget, S.A., Ulloa, M., Mitchell-Mccallister, D. 2022. Simulated irrigation water productivity and related profit effects in U.S. Southern High Plains cotton production. Agricultural Water Management. 266. https://doi.org/10.1016/j.agwat.2022.107582.
DOI: https://doi.org/10.1016/j.agwat.2022.107582

Interpretive Summary: The Ogallala aquifer under the Southern High Plains (SHP) is an important groundwater resource for U.S. cotton production, but because pumping rates exceed the aquifer’s recharge rates its water levels are steadily declining. To ensure that the aquifer’s remaining water is used productively, farmers need to know which irrigation practices use the aquifer’s water most efficiently in cotton production. To define the most efficient irrigation practices for SHP farmers, ARS scientists from Lubbock conducted cotton crop model simulations in which the amount and timing of irrigation was independently varied during the growing season. The simulations showed that maximum irrigation water use efficiency, that is, the amount of lint yield produced per inch of applied irrigation, occurred when between 12 to 14 inches of irrigation was applied. Simulations that varied irrigation timing showed that when 12 inches was applied only during the cotton crop’s mid-stage reproductive and late-stage maturation periods, irrigation efficiency was increased even further. The results of this research provides important irrigation management guidelines that will allow SHP cotton producers to maximize the ‘crop per drop’ of the remaining groundwater of the southern Ogallala aquifer.

Technical Abstract: To explore management practices that increase irrigation water use efficiency (IWUE) in U.S. Southern High Plains (SHP) cotton production, the CROPGRO-Cotton crop simulation model was used to evaluate the yield, efficiency, and profit effects of irrigation amount and timing. Using 2005-2019 weather input data from 21 SHP weather stations, lint yields were simulated for each of the 315 station-years under dryland conditions and 18 increasing total irrigation (TIRR) levels. As TIRR was increased to 55.9 cm median lint yields asymptotically approached a maximum. However, irrigation above 35.6 cm increased the incidence of total irrigation plus growing season rainfall exceeding 100% of potential crop ET, leading to decreasing marginal yield effects and decreasing IWUE. The highest median IWUE (0.321 kg m-3) was found with both 33.0 and 35.6 cm of total irrigation, with 30.5 cm providing slightly lower IWUE (0.320 kg m-3). In analyses of irrigated profitability under varying lint price and pumping cost conditions, 30.5 cm (12.0 in) of irrigation increases profits relative to dryland conditions under all but low lint price and high pumping cost conditions. But as TIRR is reduced the probability of these positive profit effects become similar to an evenly weighted coin flip at about 17.8 cm (7.0 in). Simulations that varied the timing of 30.5 cm of irrigation increased median IWUE up to 0.434 kg m-3 by limiting irrigation to cotton’s reproductive and maturation periods, with no irrigation during the initial vegetative period. As a result, these simulations indicate that applying 30.5 to 35.6 cm (12.0 to 14.0 in) of irrigation during cotton’s reproductive and maturation phases, with little or no vegetative irrigation, maximizes IWUE in SHP cotton production under current climate conditions.