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United States Department of Agriculture

Agricultural Research Service

Title: True Versus Natural Texture of Selected Soils

Authors
item Unger P W,
item Pringle F B, - SCS

Submitted to: Trends in Agricultural Sciences Soil Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 12, 1995
Publication Date: N/A

Interpretive Summary: Soil texture is based on the sand, silt, and clay content of a soil and is determined by a standard method that uses distilled water and a dispersant. However, results obtained with the standard method may not indicate the micro-aggregation that may occur when field soils are wetted by precipitation or irrigation water. This study compared the texture of nine esoils using the standard hydrometer (SH) method and the hydrometer method without a dispersant using distilled water (H+DW), well water (H+WW), or rain water (H+RW). Water retention, aggregate stability, and crust strength of the soils as affected by water quality were compared also. The H+DW and H+RW methods indicated more sand and silt and less clay than the SH method in all soils. In many cases, sand, silt, and clay determined with H+DW and H+RW methods were not different. The H+WW, H+DW, and H+RW methods indicated similar sand contents, but silt was always greater and clay was always zero with the H+WW method. Water quality did not affect soil water retention and aggregate stability and gave variable results regarding soil crust strengths. This study indicates that soils in the field may behave differently than what may be inferred from texture determinations using the SH method. Hence, it may be of value to determine texture with the SH method and a modified hydrometer method using the water that is involved under field conditions. Such information should be valuable for making management decisions that affect soil crusting, which, for example, can affect seedling emergence, water infiltration, and soil erosion.

Technical Abstract: A standard laboratory method involving distilled water and a dispersant is used to determine the true texture of soils, but the results may not reflect the micro-aggregation that can occur when field soils are wetted by precipitation or irrigation water. This study compared the true texture of soils determined by the standard hydrometer (SH) method with the 'natural' texture determined by the hydrometer method without a dispersant using distilled water (H+DW), well water (H+WW), or rain water (H+RW). Soil water retention, aggregate stability, and crust strength as affected by water quality were compared also. Compared to the SH method, the H+DW and H+RW methods indicated more sand and silt and less clay in all soils. In many cases, sand, silt, and clay determined with H+DW and H+RW methods were not different. The H+WW, H+DW, and H+RW methods indicated similar sand contents, but silt was always greater and clay was always zero with the H+WW method. Water retention and aggregate stability were not affected by water quality. Crust strength results were variable. The study indicates that soils under field conditions may behave differently texture-wise than what may be inferred by using the SH method. Hence, true texture determination with the SH method and 'natural' texture determination with a modified hydrometer method using the water that is involved under field conditions is recommended. Such information should be of value when making management decisions that affect soil crusting, which, for example, may affect seedling emergence, water infiltration, and soil erosion.

Last Modified: 11/26/2014
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