Submitted to: American Society of Agricultural Engineers Meetings Papers
Publication Type: Other
Publication Acceptance Date: July 18, 1999
Publication Date: N/A
Technical Abstract: Runoff, due to LEPA and spray sprinkler irrigation of diked and undiked furrows, was measured from 20-m long plots on Pullman clay loam, a slowly permeable soil. Irrigation control treatment plots (100% irrigation) received sufficient 25-mm irrigations to maintain plant available water at 75% in the 1.4-m deep profile. Deficit irrigation treatment plots received 0, 40, 60 and 80% of the control treatment amount on the same day. The plots were cropped to grain sorghum, and the field had a uniform 0.25% slope in the direction of the 0.76-m spaced furrows. Cultural practices were similar to those used by farmers for high yields of irrigated grain sorghum in the southern Great Plains. LEPA socks and spray heads with flat, medium-grooved deflector plates were both spaced 1.52-m apart over alternate furrows. Runoff was measured volumetrically in steel tanks from three wheel track and three non-wheel track furrows in each plot. No sprinkler runoff occurred in all treatments with the 40% irrigation amount and with the spray/diked combination. Two-year seasonal average runoff from the spray/undiked combination with 100% irrigation was 12% of the applied water. For the LEPA/diked combination with 100% irrigation, runoff was about twice that of the spray/undiked combination with a two-year seasonal average of 22%. Large amounts of runoff occurred with the LEPA/undiked combination with two-year seasonal averages of 37, 46 and 52% for the 60, 80, and 100% irrigation treatments. For 1997, a year of near average rainfall, grain sorghum yields were significantly reduced by runoff for the LEPA/undiked combination. A drought occurred during the early part of the 1998 crop season, and grain yields were significantly reduced both with and without furrow dikes for the LEPA sprinkler method.