Submitted to: ASAE Annual International Meeting
Publication Type: Other
Publication Acceptance Date: July 29, 2001
Publication Date: July 29, 2001
Technical Abstract: The subsurface drip irrigation (SDI), low energy precision application (LEPA) and two spray irrigation methods were compared for both full and deficit irrigation of grain sorghum during the 2000 growing season. The two spray methods were LESA (low elevation spray application) applied at about the 0.3-m height and MESA (mid-elevation spray application) applied at about the 1.5-m height. Irrigation amounts ranged in 25% increments from n seasonal irrigation to 100% irrigation to fully meet evapotranspiraton (ET) calculated using grass reference ET computed with a Penman-Monteith equation and locally derived crop coefficients. Cultural practices and fertility levels were similar to those used for high-yield, on-farm grain sorghum production in the Southern High Plains. The four high efficiency irrigation methods were all evaluated under a lateral move irrigation system, so that all sorghum plots could be uniformly established with spray yirrigation. The 2000 growing season was hotter and drier than normal, and the grain yield with zero seasonal irrigation was only 0.65 Mg/ha. At the 25 and 50% irrigation levels, yields with SDI of 4.51 and 7.36 Mg/ha were significantly larger than for the other irrigation methods. At the 75 and 100% irrigation levels, however, yields with the LESA and MESA spray methods averaging 10.1 and 10.5 Mg/ha were significantly larger than for the SDI and LEPA methods. Water use efficiencies calculated from total seasonal water use and seasonal irrigation followed the same trends as the grain yields. Among the four high efficiency irrigation methods tested, the optimum irrigation method for grain sorghum is likely to vary more with the irrigation amount than with the application technology. This emphasizes the need for accurate ET information for scheduling irrigations.