Climate-informed management of irrigated cotton in Western Kansas to reduce groundwater withdrawals

Authors: Baumhardt, Roland - Louis; HAAG, LUCAS - Kansas State University; Schwartz, Robert; Marek, Gary

Submitted to: Agronomy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/12/2024
Publication Date: 6/16/2024
Citation: Baumhardt, R.L., Haag, L.A., Schwartz, R.C., Marek, G.W. 2024. Climate-informed management of irrigated cotton in Western Kansas to reduce groundwater withdrawals. Agronomy. 14(6). Article 1303. https://doi.org/10.3390/agronomy14061303.
DOI: https://doi.org/10.3390/agronomy14061303

Interpretive Summary: Irrigation in western Kansas withdraws water from the declining High Plains aquifer. This coupled with declining well pumping capacity has triggered irrigation restrictions to extend the life of the aquifer. Scientists from ARS-Bushland and Kansas State University calculated simulated yields of a drought tolerant crop, cotton, using deficit irrigation capacities and durations during backcast El Nino Southern Oscillation phases at southwest, west-central, and northwest Kansas. Simulated lint yields varied with irrigation capacity, but growing season thermal energy was limiting except in southwest Kansas, which had detectable ENSO effects on climate. Split center-pivot irrigation to focus water at higher capacities and increase the net dryland to irrigated pivot yield compared well with uniform irrigation at a low deficit capacity especially during the El Niño phase. These results may be used with forecast ENSO status for climate informed management of cotton in southwest Kansas.

Technical Abstract: Irrigation to supplement precipitation for meeting crop water use or evapotranspiration (ET) is supplied in 8 states from South Dakota to Texas by the High Plains (Ogallala) aquifer, which is essentially non-recharging south of Nebraska. Consequently, groundwater withdrawals are drawing down water tables beneath western Kansas, which has led to reduced pump productivity, deficit irrigation, adoption of alternative drought tolerant crops like cotton [Gossypium hirsutum (L.)], and greater reliance on precipitation. Our objective was to evaluate El Niño southern oscillation (ENSO) phase effects on precipitation, temperature, and climate informed irrigation of cotton grown in northwestern, west-central, and southwest Kansas locations (Colby, Tribune, Garden City). Using actual 1961-2000 location weather records partitioned into ENSO phases and the GOSSYM crop growth model, we simulated water use, growth, and yield of cotton planted in soil having 50 % plant available water for all combinations of ENSO phases and scenario irrigation periods and capacities. Growing season energy did not vary with ENSO phase at any location, but precipitation and lint yield decreased significantly in southwest Kansas during the La Niña phase. At all locations, the irrigation scenarios with greater capacity significantly increased yield, water use, crop water productivity (CWP), and leaf area index (LAI) independently of duration and with limited ENSO interaction. In southwest Kansas, irrigation strategies that focused water application on a portion of the center pivot plus the dryland balance increased net-yield, producing ~90% of the 8 week × 2.5 mm/d base yield with half of the water.