Modeling cotton growth and yield response to irrigation practices for thermally limited growing seasons in Kansas

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

Submitted to: Transactions of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/17/2020
Publication Date: 1/1/2021
Citation: Baumhardt, R.L., Haag, L., Gowda, P.H., Schwartz, R.C., Marek, G.W., Lamm, F.R. 2021. Modeling cotton growth and yield response to irrigation practices for thermally limited growing seasons in Kansas. Transactions of the ASABE. 64(1):1-12. https://doi.org/10.13031/trans.13877.
DOI: https://doi.org/10.13031/trans.13877

Interpretive Summary: Previous withdrawal for irrigation has decreased the water availability from the Ogallala Aquifer in Western Kansas. To sustain future irrigation, new regional cropping practices that use less water will need to be developed and implemented. Scientists from ARS in Bushland Texas and Kansas State University investigated deficit irrigation of cotton in western Kansas. Simulated cotton yields of various planting dates, and irrigation rates and times were compared at Colby (farthest north), Tribune, and Garden City (farthest south), Kansas. These results suggested that cotton was not well suited as a crop for Western Kansas north of Garden City.

Technical Abstract: The western Great Plains precipitation averages about 450 mm, varying little with latitude and providing from 40-80% of crop evapotranspiration (ETc). Supplemental irrigation is required to fully meet crop water-demand but pumping water from the non-recharging Ogallala or High Plains Aquifer south of Nebraska draws down water tables, leading to reduced pumping and deficit irrigation or production of an alternate drought tolerant crop like cotton [Gossypium hirsutum (L.)]. Our objective was to compare simulated cotton yield response to emergence date, irrigation capacity, and application period using a validated model at three western Kansas locations (Colby, Tribune, Garden City) with varying seasonal energy and then compare split center pivot deficit irrigation strategies with a fixed water supply (i.e., where portions of the center pivot land area are managed with different irrigation strategies). We used actual 1961-2000 location weather records with the GOSSYM simulation model to estimate yields of cotton planted into soil at a 50 % initial soil plant available water for progressively later emergence dates (DOY 145, 152, and 159) and all combinations of irrigation periods (0, 4, 6, 8, and 10 weeks beginning at first square) and capacity (2.5, 3.75,and 5.0 mm/d). Simulated lint yield and its ratio to ETc or the water use efficiency, WUE, consistently decreased with delayed plantings (emergence) and as location elevation or US latitude increased due to effects on growing season thermal energy. Depending on location, simulated cotton lint yield consistently increased (P=0.05) for scenarios with increasing irrigation capacity that promoted greater early season boll load but not for durations exceeding 4 to 6 weeks probably because later irrigation and fruiting did not complete maturation during the “short” growing season. Cotton WUE generally increased with greater yields resulting from earlier emergence and early high capacity irrigation. We calculated lower WUE where irrigation promoted more vigorous growth with added fruiting forms that delayed maturation and reduced the fraction of open bolls. The irrigation strategy of focusing water at higher capacities on a portion of the center pivot in combination with the dryland balance did not increase net yields significantly at any location since the available seasonal energy limited potential crop growth and yield response to irrigation. The overall net lint yield for focused irrigation strategies at the southwest Kansas location (Garden City) was, however, numerically larger. Based on uniform or split center pivot deficit irrigated lint yields, we conclude that cotton is poorly suited as an alternative crop for western Kansas except possibly around Garden City because of limited growing season thermal energy.