Comparative Water Use Characteristics of Six Row Crops

To help make decisions on shifting of crop species in water management strategies, information is needed on comparative water use characteristics of the principal row crops. The objective of this study was to compare the water use characteristics of six row crops grown in a replicated and randomized field experiment. Crops were corn (Zea mays L.), grain sorghum [Sorghum bicolor (L.) Moench], pearl millet [Pennisetum amerlcanum (L.) Leeke], pinto bean (Phaseolus vulgaris L.), soybean [Glycine max (L.) Merr.], and sunflower (Helianthus annuus L.). Crops were grown near Manhattan, KS, on Muir silt loam (Cumulic Haplustoll) in 1981 and on Eudora silt loam (Fluventic Hapludoll) in 1982, and near Tribune, KS, on Ulysses silt loam (Aridic Haplustoll) in both 1981 and 1982. Soil water content was determined to the 3.1-m soil profile depth by the neutron attenuation method. Measured evapotranspiration (ET) was calculated as the sum of soil water depletion, rainfall, and irrigation. Reference ET was calculated by using the original Jensen-Haise equation. The maximum value of measured ET/reference ET was greater for sunflower (1.35) than for the other five crops (ranged from 1.05 to 1.15). The mean daily water use rate of sunflower (6.1 mm d−¹) was 22% greater than the mean of the other five crops (5.0 mm d−¹). The mean dry matter water use efficiency was 17.5 Mg ha−¹ m−¹ for the group of C₃ crops (pinto bean, soybean, and sunflower) and 33.3 Mg ha−¹ m−¹ for the group of C₄ crops (corn, grain sorghum, and pearl millet). Sunflower depleted significantly more water from deeper soil depths (0.99-1.60 m) than the other five crops at Manhattan in 1981 and 1982. Our findings consistently showed that sunflower had a greater daily water use rate than the other five crops. Contribution no. 87-250-J from the Kansas Agric. Exp. Stn., Manhattan, KS.