Submitted to: Agronomy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/7/2015
Publication Date: 8/13/2015
Citation: Baker, J.T., Gitz, D.C., Stout, J.E., Lascano, R.J. 2015. Cotton Water Use Efficiency Under Two Different Deficit Irrigation Scheduling Methods. Agronomy. 5:363-373.
Interpretive Summary: Plants that suffer from water stress can’t release enough water from their leaves to cool themselves. This causes plants to heat up during the day. Plant temperatures can be automatically measured with devices called infrared thermometers. In this experiment we compared two different methods of using plant temperatures to assess the amount of plant water stress and schedule irrigations. Also included in the experiment were a well-watered control treatment irrigated at 110% of daily water use by the crop and a dry land treatment that relied on rainfall only. Seasonal crop water use ranged from 353 to 625 mm across these six treatments. As expected, cotton lint yield increased with increasing crop water use but lint yield water use efficiency displayed a significant peak near 3.6 to 3.7 kg ha-1 mm-1. Our results suggest that water use efficiency may be optimized in cotton with less water than that needed for maximum lint yield.
Technical Abstract: Declines in Ogallala aquifer levels used for irrigation has prompted research to identify methods for optimizing water use efficiency (WUE) of cotton (Gossypium hirsutum L). In this experiment, conducted at Lubbock, Texas in 2014, our objective was to test two canopy temperature based stress indices, each at two different irrigation trigger set points: the Stress Time (ST) method with irrigation triggers set at 5.5 (ST_5.5) and 8.5 h (ST_8.5) and the Crop Water Stress Index (CWSI) method with irrigation triggers set at 0.3 (CWSI_0.3) and 0.6 (CWSI_0.6). When these irrigation triggers were exceeded on a given day, the crop was deficit irrigated with 5 mm of water via subsurface drip tape. Also included in the experimental design were a well-watered (WW) control irrigated at 110% of potential evapotranspiration and a dry land (DL) treatment that relied on rainfall only. Seasonal crop water use ranged from 353 to 625 mm across these six treatments. As expected, cotton lint yield increased with increasing crop water use but lint yield WUE displayed a significant (P = 0.05) peak near 3.6 to 3.7 kg ha-1 mm-1 for the ST_5.5 and CWSI_0.3 treatments, respectively. Our results suggest that WUE may be optimized in cotton with less water than that needed for maximum lint yield.