EVALUATION OF COTTON ESTABLISHMENT STRATEGIES USING SUBSURFACE DRIP IRRIGATION (SDI) IN THE SOUTHERN HIGH PLAINS OF TEXAS
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Abstract.HighlightsPlanting date and crop row distance from SDI laterals affect final cotton plant population, lint yield and water use.Cotton rows directly above 2.03-m spaced SDI laterals should only be used late within the cotton planting window.Positioning pairs of rows nearer to 2.03-m spaced SDI laterals increased yield compared to evenly spaced rows.SDI laterals spaced 1.02 m versus 2.03 m apart increased cotton yield by 5% and water use efficiency by 7%. In the Texas High Plains (THP), water table declines in the Ogallala Aquifer and the high evaporative environment have helped motivate the transition from surface and center pivot irrigation to subsurface drip irrigation (SDI). A major challenge to wider adoption of SDI in the region is inconsistent cotton seed germination and plant establishment due to dry overwinter conditions, the difficulty of pushing irrigation water upward into the seed germination zone, and the high evaporative environment during the optimum cotton planting period. To evaluate strategies for improving cotton establishment using SDI in the Southern High Plains (SHP) of Texas, a field experiment having five crop row/ SDI lateral configurations, each with two planting dates, was conducted from 2013 to 2018 at the Texas A&M AgriLife Research Center in Halfway, Texas. Differences in final plant stands, cotton yields, cotton fiber qualities, and water productivities were determined. Averaged over planting dates and years, planting directly over 1.02-m spaced SDI laterals (Every-Row configuration) increased final plant stand by 9.5%, cotton yield by 5.1%, irrigation water use efficiencies (IWUE) by 6.7%, and irrigation value (IValue) by 6.1% over planting pairs of 1.02-m spaced rows equidistant and parallel to 2.03-m spaced laterals (Traditional configuration). Compared to the Traditional configuration, planting pairs of cotton rows 0.76 m apart with both rows closer to 2.03-m spaced SDI laterals (30-50 configuration) increased final plant stand by 9.5% and yield by 3.0%. Considering additional treatments with 2.03-m spaced cotton rows planted directly over 2.03-m spaced SDI laterals (Skip-Row configuration) and 1.02-m spaced cotton rows having one row directly over 2.03-m spaced laterals and one row not irrigated (Skip-Row Plus configuration), early plantings resulted in five-year yields of 1400 and 1600 kg ha-1, respectively. However, these yields were less than those from the late planted, Traditional treatment at 1620 kg ha-1. Also, IValues and IWUEs of both Skip-Row treatments were significantly lower (p>0.05) than those of the Traditional treatment. Based on these results, the Skip-Row or Skip-Row Plus configurations should only be used late in the cotton planting period when soil water is not available for plant establishment using the Traditional or 30-50 configurations. Advantages of Every-Row and 30-50 over the Traditional configuration must be weighed against their increased costs. Keywords: Cotton, Germination, Irrigation, Southern High Plains, Subsurface drip irrigation (SDI).
