Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 8/1/2006
Publication Date: N/A
Technical Abstract: In the Texas High Plains (THP), producers are constantly searching for water conservation methods. With a semiarid climate, declining aquifer levels and negligible aquifer recharge, the use of subsurface drip irrigation (SDI) is therefore increasing each year. However, information on the best management practices to use on cotton grown on SDI systems is lacking. In 2004, we designed a study to observe root growth and activity along with wetting patterns within a SDI field. Two varieties of cotton (Gossypium hirsutum), Paymaster HS-26 and Fibermax 958, were planted on 1-m rows with subsurface drip tape with 60 cm emitter spacings located under alternate rows. Three water treatments (2.5, 5.0, and 7.5 mm d-1) based on typical local well capacities were applied according to Biotic' signals. A dryland plot was included in this study as a control. We speculate that as the application rate of SDI increases the efficient use of rainwater decreases due to the rooting distribution of cotton. We hypothesize that higher rates of SDI cause greater root congregation around the emitter with fewer roots in the top 10-20 cm of the soil. When rainfall does occur, there are fewer roots in the top 10 cm of the profile to uptake the rainwater, thus making the water use efficiency (WUE) of higher SDI application rates less efficient. To measure soil water content, Time Domain Reflectometry (TDR), probes were placed in proximity to the emitter over the drip tape and in the corresponding dry row. Root distribution was estimated using mini-rhizotron methods, and differences in transpiration on two water rates were measured with stem flow gauges using a Dynamax Flow-32 system. In 2005, differences in transpiration and soil water evaporation rates between the 2.5 and 7.5 mm d-1 treatments suggested that there was a decrease in WUE in the 7.5 mm d-1 water treatment. These measurements have been repeated with some alterations in 2006, and the number of images from the mini-rhizotron system was increased to better quantify the overall root distribution.