Submitted to: Soil & Tillage Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/12/2002
Publication Date: 6/20/2003
Citation: Fuentes, J.P., Flury, M. Huggins, D.R., Bezdicek, D.F. Soil water and nitrogen dynamics in dryland cropping systems of Washington state, USA. 2003. Soil and Tillage Research v. 71. p. 33-47. Interpretive Summary: Soil water and nitrogen (N) are critical components of cropping systems and understanding management controls is essential for improving crop yield and optimizing water and N use in dryland cropping systems. Soil water and N were monitored for two years in adjacent growers¿ fields that had been in either long-term (greater than 13 years) conventional tillage (CT) or no-tillage (NT), in two different agroclimatic zones (annual cropping site with annual precipitation of 20 inches and a grain-fallow site with 13.5 inches of annual precipitation). Long-term no-tillage improved soil water storage with little effects on soil nitrate levels as compared to CT at the annual cropping site. In the grain-fallow site, little difference in stored water occurred between NT and CT, but soil nitrate levels had accumulated below the rooting zone of the crop. These data indicate that efforts to intensify cropping in dry regions with no-tillage may lead to greater risk of N losses to ground water.
Technical Abstract: Understanding the fate of soil water and nitrogen (N) is essential for improving crop yield and optimizing the management of water and N in dryland cropping systems. Our objective was to evaluate long-term conventional tillage (CT) and no-tillage (NT) cropping system effects on soil water and N dynamics. Soil water and N were monitored in 30-cm increments to a depth of 1.5 m for two years in adjacent growers¿ fields that had been in either long-term (greater than 13 years) CT or NT, in two different agroclimatic zones (annual cropping region with mean precipitation of more than 500 mm and grain-fallow cropping region with mean precipitation below 350 mm). At the annual cropping site: (1)volumetric water content (0 to 1.5 m) was 0.05 to 0.1 m3 m-3 less under CT than NT; (2) crop modeling indicated winter surface runoff in CT but not NT;(3) differences in water dynamics between CT and NT were controlled by surface residues; and (4)soil nitrate dynamics were similar for NT and CT. At the grain-fallow site: (1) differences in soil water between NT and CT were less than 0.05 m3 m-3; and (2) high levels of soil nitrate were found after harvest below root zone under NT.