Modeling Cotton Growth and Yield Response to Irrigation Practices for Thermally Limited Growing Seasons in Kansas

Abstract

HighlightsLater planting and greater site elevation or latitude decreased seasonal growing degree days and cotton yield in Kansas.Higher irrigation capacity (rate) usually increased lint yield, which was probably due to increased early boll load.Strategies for splitting land allocations between high irrigation rates and dryland did not increase production.Cotton may reduce irrigation withdrawals from the Ogallala aquifer, but the Kansas growing season limits production.Abstract. Precipitation in the western Great Plains averages about 450 mm, varying little with latitude and providing 40% to 80% of potential crop evapotranspiration (ETc). Supplemental irrigation is required to fully meet crop water demand, but the Ogallala or High Plains aquifer is essentially non-recharging south of Nebraska. Pumping water from this aquifer draws down water tables, leading to reduced water availability and deficit irrigation to produce an alternate crop such as cotton (Gossypium hirsutum L.) with a lower peak water demand than corn (Zea mays L.). Our objective was to compare simulated cotton yield response to emergence date, irrigation capacity, and application period at three western Kansas locations (Colby, Tribune, and Garden City) with varying seasonal energy or cumulative growing degree days (CGDD) and 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 50% plant-available water for three emergence dates (DOY 145, 152, and 159) and all combinations of irrigation period (0, 4, 6, 8, and 10 weeks beginning at first square) and capacity (2.5, 3.75, and 5.0 mm d-1). Simulated lint yield and its ratio to ETc, or water use efficiency (WUE), consistently decreased with delayed planting (emergence) as location elevation or latitude increased due to effects on growing season CGDD. Depending on location, simulated cotton lint consistently increased (p = 0.05) for scenarios with increasing irrigation capacity, which 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 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 because the available seasonal energy limited potential crop growth and yield response to irrigation. However, the overall net lint yield was numerically larger for focused irrigation strategies at the southwest Kansas location (Garden City). Based on lint yields simulated under uniform or split center pivot deficit irrigation, we conclude that cotton is poorly suited as an alternative crop for central western and northwestern Kansas because of limited growing season CGDD. Keywords: Cotton, Crop simulation, Deficit irrigation, Evapotranspiration, Irrigation capacity, Split center pivot irrigation, Water use efficiency, Yield limiting factors.

Climate-Informed Management of Irrigated Cotton in Western Kansas to Reduce Groundwater Withdrawals

“…The model lint yield uncertainty under both dryland and irrigated conditions was validated for the Texas High Plains and in southwest Kansas, which indicated agreement between limited observed and modeled trials [10,31]. The 2006 to 2012 mean lint yields of multiple cultivars grown southwest of Garden City, near Hugoton, were regressed on the GOSSYM modeled cotton lint yield of one common variety file with good agreement, R 2 = 0.93, [10]. Observed higher, 1600-1800 kg ha −1 , yield levels were underestimated 10-20% by GOSSYM, possibly because the specified N fertility level was insufficient above 1200 kg ha −1 .…”

“…Model uncertainty for plant height, leaf area index, and simulated water use was previously validated under semiarid conditions that showed calculated ET values were within 10% of measured use [30]. The model lint yield uncertainty under both dryland and irrigated conditions was validated for the Texas High Plains and in southwest Kansas, which indicated agreement between limited observed and modeled trials [10,31]. The 2006 to 2012 mean lint yields of multiple cultivars grown southwest of Garden City, near Hugoton, were regressed on the GOSSYM modeled cotton lint yield of one common variety file with good agreement, R 2 = 0.93, [10].…”

“…Based on an empirical growing season cumulative thermal energy (CGDD) model, Gowda et al [9] concluded that well-watered cotton was a suitable alternative crop for southwest Kansas that could reduce water use. Using mechanistic crop growth simulation, Baumhardt et al [10] estimated average water use of deficit irrigated cotton at ~460 mm in western Kansas, which is 30% less than the ~650 mm ET value for fully irrigated corn [11,12]. The relatively small cotton yields in the northwest and west-central areas of Kansas, regardless of the irrigation level, combined with costs for non-routine production, may be insufficient for risk-averse producers to change principal crops [10].…”

Policy, Technology, and Management Options for Water Conservation in the Ogallala Aquifer in Kansas, USA

“…Similarly, Himanshu et al [47] found that imposing water deficits in the initial or final growth stages had little effect on seed cotton yield, while the peak bloom growth stage (GS4) was the most sensitive stage to water stress. While cotton has not been a common crop in western Kansas, it has the potential to produce net returns comparable to corn, and Baumhardt et al [48] found that short season, early planted cotton could be a viable, low-water requirement crop in the southwestern part of Kansas.…”

Beyond 2020, Vision of the Future: Selected Papers from the Sixth Decennial National Irrigation Symposium

“…Cotton requires less irrigation than corn and thus has become an irrigated crop of interest in western Kansas despite the limited thermal units available for production. Modeling was used to examine the effects of crop emergence date, irrigation capacity, and irrigation application period on cotton production in three western Kansas locations (Baumhardt et al, 2020). Earlier emergence generally increased yield and water productivity.…”