Impacts of Intensified Cropping Systems on Soil Water Use by Spring Wheat

In semiarid dryland farming regions, No-till and intensified crop rotations may improve water use. Our objective was to determine water use efficiency (WUE) and precipitation use efficiency (PUE) for spring wheat (Triticum aestivum L.; SW) grown in crop sequences representing different levels of intensification, under minimum (Min-till) or No-till. Root zone (0–122 cm) water at planting (SWP) was 2.76 cm higher for two- and three-phase sequences under Min-till than continuous spring wheat (CSW), and sequences with fallow averaged 2.65 cm higher than those without. Conversely, SWP was unaffected by sequence under No-till, with less effect of fallow. Root zone water at harvest was unaffected by the number of crop phases or fallow under Min-till. However, values for CSW exceeded the two- or three-phase sequences by 1.57 and 2.53 cm under No-till, and sequences without fallow averaged 1.52 cm more than those with fallow. The highest WUE (8.4 kg grain ha⁻¹ mm⁻¹ water) was observed when SW was grown in three-phase sequences compared with 7.7 kg grain ha⁻¹ mm⁻¹ water, for CSW and SW-fallow. Spring wheat under Min-till had higher WUE in sequences with fallow, but no effects of fallow occurred with No-till. The lowest PUE (near 3 kg grain ha⁻¹ mm⁻¹ precipitation) and no effects of tillage were found in sequences with fallow. However, SW in continuously cropped sequences had PUE between 5.5 and 6.4 kg grain ha⁻¹ mm⁻¹ precipitation and was higher under No-till. Both WUE and PUE are affected by intensification but may also be influenced by patterns of weather.