Leveraging Rainfall with Very Limited Irrigations in Texas High Plains Cotton Rotations

Significant changes such as declining water tables and the need for crops other than cotton are occurring on the Texas South Plains and affecting production decisions. Field evaluations are being conducted to compare yield and total water use from a continuous cotton cropping system to cotton in three-year rotations that replaces every third cotton crop with 1) BMR forage sorghum, non-BMR forage sorghum, safflower, and sunflower (from 2013 to 2016) and 2) corn and sorghum at two populations (from 2017 to 2018). Seasonal irrigation volumes are limited to 0, 3 and 6 inches of depth per year. In years following a previously “dry” year, cotton yields and WUEs tended to be higher in continuous cotton treatments compared to those from cotton rotations. With some exceptions, in years following a previously “average” or “above average” rainfall year, the alternative crop rotations tended to result in similar cotton yields and WUEs as continuous cotton. In all years, increases in WUE occurred with each incremental increase in seasonal irrigation indicating that concentrating available irrigation on smaller land areas may be the better water use option than spreading irrigations over larger areas. To date there are no results indicating cotton in rotation with an alternate crop produced consistently higher or lower yield than continuous cotton.  However, within a given year, gross water values have been significantly higher when irrigations were applied to cotton rather than an alternative crop.