A pproximately 8 million cattle are on feed in the central and southern Great Plains of the USA; more than 2 million are in Kansas alone. Using the Kansas design parameter of 23 m 2 per animal, the land area of feedlots in the Great Plains is approximately 18 400 ha, and that in Kansas is approximately 4600 ha. Phillips (1981) estimated that 20 to 33% of average annual precipitation in the Great Plains could be collected as runoff from feedlots. Using the lower end of that range (20%) and assuming an average annual precipitation of 500 mm, averages of approximately 4.6 × 10 6 m 3 of runoff from feedlots might be available annually in Kansas and 18.4 × 10 6 m 3 in the Great Plains. Areas of higher rainfall would collect more runoff, and the amount collected would vary from year to year, based on precipitation. This feedlot runoff, minus any evaporation from the lagoons, must be disposed of by land application. Using subsurface drip irrigation (SDI) with water from animal waste lagoons (hereinafter called wastewater) has many potential advantages. These include, but are not limited to, reduced human contact with wastewater; reduced odor; reduced runoff of wastewater into surface waters; placement of phosphorus-rich water beneath the soil surface where runoff potential is reduced; greater uniformity of water application resulting in better control of the water, nutrients, and salts; reduced corrosion of irrigation systems; reduced application constraint by weather (especially high winds and low temperatures); and increased flexibility in matching field and irrigation system sizes. Research has shown that soil acts as an additional treatment (or filter) for municipal wastewater applied through an SDI system. Oron (1996) injected poliovirus into the soil with an SDI system. He found limited virus content in the leaves of tomato (Lycopersicon esculentum Mill.) plants but none in the fruit. No fecal coliforms were found in the ears or husks of sweet corn (Zea mays L.) irrigated using secondary treated municipal wastewater with SDI; whereas, some contamination was found in corn irrigated with surface drip irrigation (Oron et al., 1991). Oron et al. (1992) noted that sprinkler irrigation with secondary treated municipal wastewater was less desirable than drip irrigation with respect to viral and bacterial contamination of soils and plants. Treated wastewater also has been applied successfully though SDI systems in Hawaii (Gushiken, 1995). Treated residential wastewater, which is not as highly treated as municipal effluent, has also been disposed with SUBSURFACE DRIP IRRIGATION USING LIVESTOCK W ASTEWATER: DRIPLINE FLOW RATES T. P. Trooien, F. R. Lamm, L. R. Stone, M. Alam, D. H. Rogers, G. A. Clark, A. J. Schlegel ABSTRACT. Using subsurface drip irrigation (SDI) with lagoon wastewater has many potential advantages. The challenge is to design and manage the SDI system to prevent emitter clogging. The objective of this study was to measure the flow rates 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 lagoon wastewater. A disk filter with openings of 55 μm (200 mesh) was used and shock treatments of chlorine and acid were injected periodically. During the 1998 growing season, 530 mm of wastewater were applied through the SDI system and 390 mm were applied in 1999. During the growing seasons, the two lowest flow rate emitter designs decreased in flow rate, indicating that some emitter clogging had occurred. The magnitudes of the decreases were 15% and 11% of the original 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 designs with higher flow rates showed little sign of clogging; their flow rates decreased by 4% or less through both growing seasons. Observations showed that the disk filter and automatic backflush controller performed adequately in 1998 and 1999. Based on these preliminary results, the use of SDI with lagoon wastewater shows promise. However, the smaller emitter sizes (0.91 L/h/emitter or less) may be risky for use with wastewater and the long-term (greater than two growing seasons) effects are untested. Keywords. Microirrigation, Drip irrigation, Trickle irrigation, Animal waste management, SDI, Wastewater. Article was submitted for publication in December 1999; reviewed and approved for publication by the Soil & Water Division of ASAE in June 2000. Mention of product name is for information only and does not imply endorsement. Contribution No. 00-198-J from the Kansas State University Agricultural Experiment Station, Manhattan, Kansas. The authors are Todd P Trooien, ASAE Member Engineer, Associate Professor, Agricultural and Biosystems Engineering Dept., South Dakota State University, Brookings, S. Dak.; Freddie R Lamm, ASAE Member Engineer, Professor, Northwest Research-Extension Center, Kansas State Univ., Colby, Kans.; Loyd R Stone, Professor, Department of Agronomy, Kansas State Univ., Manhattan, Kans.; Mahbub Alam, ASAE Member Engineer, Assistant Professor, Southwest Area Extension Office, Kansas State Univ., Garden City, Kans.; Danny H. Rogers, ASAE Member Engineer, Professor, and Gary A Clark, ASAE Member Engineer, Professor, Dept. of Biological and Agricultural Engineering, Kansas State Univ., Manhattan, Kans.; and Alan J Schlegel, Professor, Southwest Research-Extension Center, Kansas State Univ., Tribune, Kans. Corresponding author: Todd P. Trooien, South Dakota State University, Agricultural and Biosystems Engineering Dept., Box 2120, Brookings, SD 57007, phone: 605.688.5141, fax: 605.688.6764, e-mail: <todd_trooien@sdstate.edu>. Applied Engineering in Agriculture VOL. 16(5): 505-508 © 2000 American Society of Agricultural Engineers 0883-8542 / 00 / 1605-505 505 sw 3508 ms 8/21/01 9:01 AM Page 505