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United States Department of Agriculture

Agricultural Research Service

Title: Distribution and Variability of Surface Soil Properties at a Regional Scale

Authors
item Brejda, John
item MOORMAN, THOMAS
item Smith, Jeffrey
item KARLEN, DOUGLAS
item Allan, D. - UNIVERSITY OF MINNESOTA
item DAO, THANH

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 1, 1999
Publication Date: N/A

Interpretive Summary: Soil quality is as important to our society as water and air quality. Soils provide structural stability for houses and road as well as a medium for plant growth. The development of soils gives us the varied environment in which we live, from beautiful pristine forests to fields of wheat that provide us with nutrition. Worldwide soils are degrading due to the human obsession to reproduce to maximum environmental capacity. We need measure to evaluate the changes in soil quality do to these influences so that we can develop management strategies to increase or maintain soil quality. In this study, we evaluated soils from different areas of the U.S. for 17 biological, physical and chemical attributes indicative of changes in soil quality. Most of the parameters we measured were highly variable and varied between areas. Only a few parameters could be used for regional analysis of soil quality but the precision was good enough to detect changes. This analysis should help in future work on soil degradation and soil quality.

Technical Abstract: Information on the probability distribution and variability of soil properties at a regional scale could improve the ability of the USDA- Natural Resources Conservation Service (NRCS) to monitor soil condition using the National Resources Inventory (NRI). Our objective was to evaluate the hypothesis that the probability distribution of 17 physical, chemical, and biological soil properties are: (1) normally distributed, or (2) log-normally distributed at a regional scale, and to estimate the magnitude of change that may be detected assuming either a normal or log- normal distribution. Samples were collected irrespective of soil series from two Major Land Resource Areas (MLRA) (9 and 105), and from the Ascalon (Fine-loamy, mixed, superactive, mesic Aridic Argiustoll) and Amarillo (Fine-loamy, mixed, superactive, thermic Aridic Paleustalf) soils in MLRA 67 and 77, using the NRI sampling design. Most soil properties were non- normally distributed, with the frequency of non-normality varying between MLRAs. Confining sampling to a single soil series did not consistently improve the precision with which soil properties were estimated. Natural log transformation resulted in normal distributions for most soil properties and reduced variability 2- to 3-fold. However, a few soil properties remained non-normally distributed. Soil pH may be monitored at the regional scale with a high degree of precision. Small changes in soil carbon (C) content (3 to 8% of the regional mean) may be detected using ln transformed total organic C as the indicator. Sampling soil properties as part of the NRI should improve NRCS' ability to monitor soil condition on a regional scale.

Last Modified: 8/19/2014
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