Subsurface Drip Irrigation Research on Commodity Crops in North Carolina

Abstract

Subsurface drip irrigation (SDI) is relatively new to North Carolina. Subsurface drip, for purposes of this paper, means drip line installed at a depth below normal tillage operations, and used multiple years. There has been interest of the use of this technology on commodity crops (corn, wheat, soybeans, cotton, and peanuts) upon which much of the North Carolina agricultural economy is based. Research-scale SDI systems have been installed in the Piedmont of North Carolina, in clay loam soils, and in the Coastal Plain in fine sandy loam soils. One year of data has been collected for corn, winter wheat, and soybeans in the Piedmont, and for cotton and peanuts at the Coastal Plain site. The Piedmont site tested for impact of drip line spacing on corn, winter wheat and soybean yield, while the initial phase of the coastal plain site tested the effect of irrigation method (SDI, sprinkler, and rainfed) and pest strategies on cotton and peanut yield. Data from the Piedmont site indicated that a 5-foot drip line spacing (every-other-row between-rows) on corn was just as effective as a 2.5-foot spacing (every-row under-row). No increase in winter wheat yield was realized for any of the drip line spacings, however the wheat was replanted due to cold, dry weather, and was poorly established, complicating the comparison. SDI irrigated soybean yield was also not statistically different than rainfed yield for any of the drip line spacings. This may have been due to the combination of an early frost and indeterminate soybeans that negated potential irrigation benefits late in the pod filling stage. Data from the Coastal Plain site showed that SDI improved cotton yield as compared to sprinkler across Roundup. and Pix. treatments. Peanuts receiving various disease control strategies had similar results. Continued research is planned for both sites.