SUBSURFACE DRIP IRRIGATION USING LIVESTOCK WASTEWATER: DRIPLINE FLOW RATES

Abstract

Using subsurface drip irrigation (SDI) with lagoon wastewater has many potential advantages. The challengeis to design and manage the SDI system to prevent emitter clogging. The objective of this study was to measure the flowrates of five types of driplines (with emitter flow rates of 0.57, 0.91, 1.5, 2.3, and 3.5 L/h/emitter) when used with lagoonwastewater. A disk filter with openings of 55 m (200 mesh) was used and shock treatments of chlorine and acid wereinjected periodically. During the 1998 growing season, 530 mm of wastewater were applied through the SDI system and390 mm were applied in 1999. During the growing seasons, the two lowest flow rate emitter designs decreased in flowrate, indicating that some emitter clogging had occurred. The magnitudes of the decreases were 15% and 11% of theoriginal flow rates in 1998 and 22% and 14% in 1999 for the 0.57 L/h/emitter and 0.91 L/h/emitter driplines, respectively.After the winter idle period, the flow rates of both driplines returned to the initial flow rates. The three emitter designswith higher flow rates showed little sign of clogging; their flow rates decreased by 4% or less through both growingseasons. Observations showed that the disk filter and automatic backflush controller performed adequately in 1998 and1999. Based on these preliminary results, the use of SDI with lagoon wastewater shows promise. However, the smalleremitter sizes (0.91 L/h/emitter or less) may be risky for use with wastewater and the long-term (greater than two growingseasons) effects are untested.