Longevity and Performance of a Subsurface Drip Irrigation System

System longevity is an important economic factor to minimize amortized investment costs for subsurface drip irrigation (SDI), especially when growing lower-value commodity crops such as field corn. Kansas State University established a research site in 1989 at a research center to study SDI. One research study area was used for continuous production of SDI corn for 27 seasons without dripline replacement. Normalized plot flowrates for 23 separate plots after 27 seasons were within ±5% of their first annually measured value. Hydraulic performance of the driplines and emitters was measured and in the laboratory for excavated dripline samples after the SDI system was decommissioned in the fall of 2015. There were similar results from both and laboratory tests of the used driplines, with excellent coefficients of variation (CV) of approximately 3%, lower quartile distribution uniformities (DUlq) of 96 to 97, and Christiansen uniformity coefficients (UC) of approximately 98. The performance results of the excavated driplines were as good as or better than the performance of some unused driplines that had been in storage since 1990. Long SDI system life appears possible in the U.S. Central Great Plains when the systems are properly designed, installed, and maintained. The long system life (27 seasons and 26.5 years) improves the economic competitiveness of SDI with alternative irrigation systems such as center-pivot sprinkler systems, which are currently the predominant irrigation system in the region. The SDI system was decommissioned at the end of the 2015 crop growing season due to leaks arising from breakdown in the plastic material, rather than due to any clogging concerns and subsequent lower application uniformity. Keywords: Distribution uniformity, Drip irrigation, Flow variation, Microirrigation, Subsurface drip irrigation.