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United States Department of Agriculture

Agricultural Research Service

Title: Spatial Relationships among Soil Physical Properties in a Grass-Alfalfa Hay Field

Authors
item Jabro, Jalal "jay"
item Stevens, William
item Evans, Robert

Submitted to: Soil Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 19, 2006
Publication Date: November 1, 2006
Repository URL: http://handle.nal.usda.gov/10113/50500
Citation: Jabro, J.D., Stevens, W.B., Evans, R.G. 2006. Spatial relationships among soil physical properties in a grass-alfalfa hay field. Soil Science. 17:719-727.

Interpretive Summary: The spatial variation of cone index, bulk density, volumetric moisture content, sand and clay content in the surface horizon of a sandy loam soil was assessed. The goestatistical methods revealed spatial variability in cone index at 50-100 mm and 200-250 mm depths, bulk density, moisture content, sand and clay content across the field. The variability of these soil physical properties exhibited medium to strong spatial dependence that could be well described using either spherical or exponential models. The semivariogram for clay content shows a small range of spatial dependence and approximately zero nugget effect. Positive correlations indicated that direct relationships existed between bulk density and cone index (r = 0.57, P < 0.01) at 50-100 mm depth and between moisture content and content of clay (r = 0.58, P < 0.01) in the soil. Further, weaker correlations were among other soil properties at both depths. Spatial variability of soil physical properties is due to a combination of previous farming practices, vegetation history, erosion, and weather conditions.

Technical Abstract: Knowledge of the spatial variability of soil physical properties is important for site-specific soil management. The objectives of this study were to characterize the field-scale spatial variability of cone index, bulk density, volumetric moisture content, sand and clay content in the A horizon of a Lihen sandy loamy soil (sandy, mixed, frigid Entic Haplustoll), and to describe the relationship among these soil physical properties. This study was conducted on grassland site of approximately 4.75 ha that has been in rain-fed crested wheatgrass-alfalfa hay production for over 20 years. Soil bulk density was determined from samples collected using a core sampler while cone index was measured by inserting a digital penetrometer into the soil at three different locations within a 300-mm radius of where the bulk density samples were extracted. The measurements were made on a 16 m 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 50-100 and 200-250 mm. Soil parameters were modeled as normally distributed random variables. Cone index at 50-100 mm and 200-250 mm depths, bulk density, moisture content, sand and clay content exhibited medium to strong spatial dependence that was well described using either spherical or exponential models. The semivariogram for clay content shows a small range of spatial dependence and nearly zero nugget effect. Positive correlations indicated that direct relationships existed between bulk density and cone index (r = 0.57, P < 0.01) at 50-100 mm depth and between moisture content and content of clay (r = 0.58, P < 0.01) in the soil. Spatial variability of soil physical properties were attributed to a combination of previous farming practices, vegetation history, erosion, and weather conditions. The degree of variability in soil physical properties was concluded to be of sufficient magnitude to influence the spatial distribution of crop yield thus having considerable implications regarding the implementation of site-specific management practices.

Last Modified: 10/20/2014
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