Spatial Variability of Hydraulic Conductivity in a Cultivated Field at Different Times
Farming practices and climatic patterns may alter soil surface hydraulic conductivity (K) both spatially and at different times during a season. This study quantified spatial variability and spatial dependence of ponded and tension K measurements in a cultivated field at different times. Paired small-base infiltrometers (76-mm diameter) were used at four pressure heads (5, −30, −60, and −150 mm) to measure K across a transect four times during one and a half growing seasons (1–2 July 1991, 12–13 Aug. 1991, 29–30 Apr. 1992, and 28–29 May 1992). A natural log transformation best normalized ponded K data, but ln(K + 1) was better for the tension data. Periodicity was apparent for K at a head (h) of −150 mm, with a significant period of 46 m for July 1991, 147 m for April 1992, and 96 m for May 1992. The periods for the three dates may be three different harmonics. The July periodicity was consistent with expected wheel traffic patterns from the previous harvest; K measurements would have coincided with wheel tracks every 46 m for the July 1991 measurement date. Periodicity for other dates had no apparent cause. For ponded K, only within-pair data were spatially correlated (0.6–0.8 m). At a head of −150 mm, K values were spatially correlated over distances of 6.6, 16.8, and 0.6 m for the measurements of July 1991, April 1992, and May 1992, respectively. Correlation distances were intermediate for K-30 and K-60. Since spatial correlation and periodicity varied with measurement date, one set of transect measurements was not adequate to describe spatial variability of K.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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