Wednesday, 9 November 2005
7

Spatial Variability of Physical Properties in Lihen Sandy Loam Soil.

Jay D. Jabro, Bart Stevens, and Robert Evans. NPARL ARS-USDA, 1500 N Central Avenue, Sidney, MT 59270

Knowledge of the spatial variability of soil physical properties is important for precision agriculture. The spatial variation of soil bulk density (rb), cone index (CI), and gravimetric water content (θv) in a loamy sand soil was assessed using several geostatistical techniques and traditional statistics. Field data from a research farm located near Williston, ND was used to evaluate the variability of rb, CI, and θv and to determine whether they were correlated with each other. Soil bulk density was determined from samples collected using a core soil sampler while cone index was measured by inserting a hand-held digital penetrometer into the soil at three different locations within a 30-cm radius of where the rb samples were extracted. The measurements were made on a 16 m Χ 36 m grid sampling system, which created 72 individual grid cells. Soil properties were measured at the center of each grid cell at depths of 5-10 and 20-25 cm. The three soil parameters were modeled as normally distributed random variables. Sample coefficients of variation were smallest for rb and largest for CI; a significant correlation was identified between rb and CI at both depths. Further, a weak correlation was found between CI and θv. Sample semivariograms were also constructed for each soil property and were described by combinations of pure nugget and spherical model structures.

Handout (.pdf format, 990.0 kb)

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