Sprinkler evaporation losses in alfalfa during solid-set sprinkler irrigation in semiarid areas

Gross sprinkler evaporation losses (SEL_g) can be large and decrease irrigation application efficiency. However, it is not universally established how much of the SEL_g contributes to decrease the crop evapotranspiration during the sprinkler irrigation and how much are the net sprinkler losses (SEL_n). The components of SEL were the wind drift and evaporation losses (WDEL) and the water intercepted by the crop (IL). The gross WDEL (WDEL_g) and evapotranspiration (ET) were measured simultaneously in two alfalfa (Medicago sativa L.) plots, one being irrigated (moist, MT) and the other one not being irrigated (dry, DT). Catch can measurements, mass gains, and losses in the lysimeters and micrometeorological measurements were performed to establish net WDEL (WDEL_n) during the irrigation and net IL (IL_n) after the irrigation as the difference between ET_MT and ET_DT. Also, equations to estimate IL_n and net sprinkler evaporation losses (SEL_n) were developed. IL_n was strongly related to vapor pressure deficit (VPD). SEL_n were 8.3 % of the total applied water. During daytime irrigations, SEL_n was 9.8 % of the irrigation water and slightly less than WDEL_g (10.9 %). During nighttime irrigations, SEL_n were slightly greater than WDEL_g (5.4 and 3.7 %, respectively). SEL_n was mainly a function of wind speed.