Agronomic and economic effect of irrigation rate in cotton

Authors: Lamb, Marshall; Sorensen, Ronald - Ron; NUTI, R - Dow Agrosciences; Butts, Christopher - Chris; EIGENBURG, D - Georgia Soil And Water Conservation Commission

Submitted to: Crop, Forage & Turfgrass Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/16/2015
Publication Date: 5/15/2015
Publication URL: http://dx.doi.org/10.2134/CFtm2014.0061
Citation: Lamb, M.C., Sorensen, R.B., Nuti, R.C., Butts, C.L., Eigenburg, D. 2015. Agronomic and economic effect of irrigation rate in cotton. Crop, Forage, & Turfgrass Management. doi: 10.2134/cftm2014.0061.

Interpretive Summary: Irrigation is essential to sustain cotton yield and net returns during most years in the Southeast. Producers realize that irrigation is important as irrigated cotton, corn, and peanut acreage in Georgia has increased in recent years. However, demand for water resources due to urban expansion and interstate litigation coupled with repeated drought are collectively threatening irrigation water supplies in the Southeast. Next to land, abundant water for irrigation is arguably the most important natural resource in production agriculture. Data and information on cotton yield, water use efficiency (WUE), water use efficiency from irrigation (WUEi), and the returns from irrigation in terms of water use efficiency (RWUEi) in cotton is limited. A study was conducted at the USDA/ARS Multi-crop Irrigation Research Farm in Shellman, GA during the 2001-2012 crop years to examine the impact of irrigation rate on cotton in Georgia. Irrigation rates consisted of 100, 66, 33%, and a non-irrigated control. These data were separated based on precipitation received into below average and above average precipitation groups. Irrigation consistently increased lint yield regardless of precipitation amount. Response for WUE, WUEi, and RWUEi was different across irrigation rates depending on precipitation grouping. Maximum yield and net returns resulted in the 100% irrigation treatment while maximum WUE, WUEi, and RWUEi resulted in the 66% irrigation treatment during the below average precipitation group. Thus, because of inconsistent rainfall distribution and resulting crop stress, cotton in the humid Southeast region should be produced in fields with adequate irrigation capacity.

Technical Abstract: Although the Southeast U.S. receives an average annual precipitation of 1300 mm, cotton (Gossypium hirsutum L.) yield is often limited by erratic seasonal distributions. Studies were conducted from 2001 through 2012 at the USDA/ARS Multi-crop Irrigation Research Farm in Shellman, GA (84' 36' W, 30' 44' N) on a Greenville fine sandy loam (fine, kaolinitic, thermic Rhodic Kandiudults). Irrigation rates of 100, 66, 33%, and a non-irrigated control were addressed with the 100% treatment following the recommendations of Irrigator Pro for Cotton (a model developed by USDA/ARS for irrigation scheduling in cotton) and the other rates were applied at the same time and in proportion to the 100% treatment. The objective of this 12-yr study is to evaluate the effects of irrigation depth on lint yield, net returns, water use efficiency, water use efficiency to irrigation, and returns to water use efficiency to irrigation for cotton produced in the humid southeast region of the U.S. The 100% irrigation treatment increased lint yield compared to non-irrigated yield in 10 of the 12 years and increased net return over variable cost 8 of the 12 years. The highest and lowest lint yields resulted in the 100% and non-irrigated treatment in the years of below average precipitation, respectively. WUE, WUEi, and RWUEi responded differently across irrigation amounts depending on precipitation grouping. The highest WUE and WUEi occurred in the 66% irrigation amount during the below average rainfall years at 57.06 and 92.68 kg ha-1cm-1, respectively. The highest RWUEi also occurred in the 66% rate during the below average rainfall years at $58.28 ha-1 cm-1.