Precipitation Use Efficiency of Soybean and Grain Sorghum in Monoculture and Rotation

Abstract

AbstractRainfed cropping systems are highly dependent on water use efficiency of crops in the rotation, especially in subhumid and semiarid areas. Precipitation use efficiency (PUE), an alternative to water use efficiency, is equally effective for water use evaluation in long‐term rainfed studies. We hypothesized that crop rotation and N fertilizer rates altered PUE of soybean [Glycine max (L.) Merr.] and grain sorghum [Sorghum bicolor (L.) Moench]. To test this, soybean (five cropping systems) and grain sorghum (four cropping systems) were grown under rainfed conditions at Mead, NE, on a Sharpsburg silty clay loam (fine, montmorillonitic, mesic Typic Argiudoll), each at three N fertilizer rates. Precipitation use efficiency values for the 1984 through 1991 cropping seasons varied from 15.5 to 59.9 and 21.6 to 159 kg ha−1 cm−1 for soybean and grain sorghum, respectively. Soybean PUE values averaged 30 kg ha−1 cm−1 and varied from 25 to 33 kg ha−1 cm−1 for the 8 yr. Grain sorghum PUE values averaged 89 kg ha−1 cm−1 and with sufficient N fertilization varied from only 94 to 99 kg ha−1 cm−1 for the 8 yr. Similar PUE values for soybean and grain sorghum (with adequate N fertilizer) within a given year and similar PUE values during the study among cropping systems for each crop indicated that both of these crops would be excellent options for rotations in areas with similar precipitation patterns.