Author
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Logsdon, Sally |
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Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 2/25/2015 Publication Date: 4/3/2015 Citation: Logsdon, S.D. 2015. Event- and site-specific soil wetting and seasonal change in amount of soil water. Soil Science Society of America Journal. 79:730-741. Interpretive Summary: Soil water does not change uniformly across a field because the water can move from one location to another. This study showed that low positions in the field had greater increases and decreases in soil water content than other sites, probably due to water flow from higher elevations. Buried tiles may have facilitated rapid drainage. Low position sites without buried tiles showed more subsurface soil water changes, probably due to greater variation in the water table depth. This information is of interest to scientists who study soil water patterns in the field. The information is also important to field operators who want to manage for variable soil water in the field to optimize crop water use (i.e., by reducing compaction and increasing residue cover to improve infiltration and reduce runoff and runon within the field). Technical Abstract: Numerous studies have examined ways to characterize the central tendency of soil water within a field or watershed. Extreme changes in water content reveal more about water movement within the area. The purpose of this study was to determine if extreme soil water changes varied among sites, and to see the contribution of crop row and landscape position on these extreme soil water changes. Nine sites were instrumented with CS616, water content reflectometers (WCR) at row and interrow positions for 0.015 and 0.045 m depths, and at one position for 0.15, 0.30, and 0.60 m depths. The calibrated hourly soil water contents were corrected for temperature and averaged to obtain daily changes in soil water. Except for crop row position analysis, the 0.015 and 0.045 four samples were averaged to one 0.03 m depth. Some sites at low relative elevation had larger daily soil water increases, presumably due to lateral additions of water. Row position across sites was only a significant factor on less than one fourth of the peak daily increases. Five of the nine sites showed significant row position effects in 2011, and six of the nine sites did in 2012. For the 0.03 m depth, landscape factors showed significant linear effects on peak daily soil water increases about 25% of the time and on daily water decreases about 40% of the time. There were few significant linear trends for the deeper depths. Overall, there were significant differences in peak daily increases and decreases across the nine sites. Crop row position and landscape factors were important contributions for some of these peak events. |
