The recent increase in the use of subsurface drip irrigation (SDI) for cotton production in the Texas High Plains has resulted in questions concerning drip lateral position and orientation relative to crop rows. Field experiments were conducted at Halfway, Texas to evaluate traditional SDI installations with crop rows spaced at 0.76 and 1.02 m; crop row to lateral offsets of 0.0, 0.13, 0.25, and 0.38 m; and crop rows perpendicularly crossing SDI laterals spaced at 0.76, 1.02, and 1.52 m. Traditionally installed SDI with cotton rows spaced at 0.76 m resulted in generally higher yield than those spaced at 1.02 in; however, differences were not significant over the 5-year period. Yields were significantly different between individual rows of adjacent row pairs irrigated with single SDI laterals when row offsets were greater than 0.25 m on 0.76-m row spacing. However, cotton plants from rows closest to the SDI lateral largely compensated for yield losses of rows farthest from the lateral. When considering perpendicularly crossing 1.52-m spaced laterals with 0.76-m wide crop rows, only modest declines in cotton lint yield (1.5% and 3.3%) occurred compared to traditional parallel row-lateral orientation with the same lateral and row spacing. With crop rows perpendicular to laterals, SDI lateral spacings resulted in average yields of 1802, 1869, and 1903 kg ha(-1) at distances of 1.52, 1.02, and 0.76 m, respectively. Orienting rows perpendicular to drip laterals using 0.76-m crop row widths resulted in significantly higher yields and irrigation water use efficiencies than 1.02-m row widths at high irrigation capacity. As water availability declines, these results will provide producers additional information on SDI installation and management.
