SUBSURFACE DRIP IRRIGATION LATERAL SPACING AND MANAGEMENT FOR COTTON IN THE SOUTHEASTERN COASTAL PLAIN

摘要

The cost of drip irrigation can be reduced by using both wider lateral spacings and the same laterals for multiple years, as with subsurface placement. Multiple, low-rate fertilizer and water applications may reduce N fertilizer needs by improving efficiency and limiting the potential for leaching. The combination of these technologies may make drip irrigation of cotton profitable. Four years of continuous cotton and two years of cotton rotated with peanut were evaluated. Two subsurface drip irrigation lateral spacings (every row, 1 m, and alternate furrow, 2 m) and three sidedress-nitrogen methods (STD, single application of 112 kg/ha; INC, 112 kg/ha in five equal applications; and GOS, applications determined by GOSSYM/COMAX) were evaluated for cotton during 1991-1994. Two of the sidedressnitrogen methods (STD and GOS) were evaluated for a rainfall-only treatment. Lint yields did not differ between the lateral spacings in any year. Yields for irrigated treatments were 16 and 65% greater than rainfall-only yields in 1992 and 1993, respectively. The GOSSYM/COMAX-managed nitrogen treatment received 30% less nitrogen fertilizer than other treatments, but had similar lint yield. Several fiber physical properties were affected by irrigation and nitrogen, but these effects were small and inconsistent. For continuous cotton, or cotton rotated with peanut, the wider lateral spacing is preferred to the every-row spacing because of its lower initial cost (about 30%). The combination of lower system cost, longer system life, and lower N-fertilizer requirements could make subsurface drip irrigation of cotton profitable for southeastern Coastal Plain soils, and reduce the potential for ground water contamination.