Dr. John W. Sij, Dr. Jeffrey E. Slosser, and Mr. David Bordovsky. Texas Agricultural Experiment Station, Box 1658, Vernon, TX 76385
Ground water resources are limited in the Texas Rolling Plains. With Cotton Foundation support, a 3-yr subsurface drip irrigation (SDI) study was initiated in Knox County in 2003. In one study, treatments included production on 40-inch and 80-inch drip tape spacing and 100% evapotranspiration (ET) replacement, furrow irrigation, and no-till in a terminated rye cover crop. In a second study, treatments included irrigation at 100% ET replacement without a rye cover crop, 50% ET replacement with and without a rye cover crop, and furrow irrigation. SDI significantly increased cotton yield over that from furrow irrigation 2 of 3 years, from 250 to 575 lb/ac. Excess rainfall in 2005 resulted in no significant differences among treatments. Loan values varied among treatments, but favored SDI-grown cotton 2 of the 3 yr. In 2003, a 50% reduction in ET replacement reduced lint yield only 18%. In 2004, there was no reduction in yield with 50% ET replacement compared with the 100% ET replacement. It appears that 100% ET replacement is not necessary to maximize yield under SDI.
