Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/12/2000
Publication Date: N/A
Interpretive Summary: Currently, the USDA-Natural Resources Conservation Service (NRCS) cannot measure soil quality at a regional scale, but would like to use the National Resources Inventory (NRI) framework. For this to be feasible, soil quality indicators are needed for use with the NRI. We conducted a pilot study using the NRI methodology in the Northern Mississippi Valley Loess Hills and Palouse and Nez Perce Prairies regions to: 1) select a se of soil quality indicators for use in these regions, 2) determine how these soil quality indicators varied with land use, and 3) compare these results with indicators selected from the Central and Southern High Plains. Rigorous statistical analysis indicated that in the Northern Mississippi Valley Loess Hills, potentially mineralizable N, microbial biomass C, water stable aggregation, and total organic C were the most sensitive soil quality indicators. In the Palouse and Nez Perce Prairies, total N and total organic C were the most sensitive soil quality indicators. Results from this study support conclusions made for a similar project in the Central and Southern High Plains regions of the U.S. We conclude that a universal, optimum set of indicators for assessing soil quality on a regional scale does not exist. However, if the NRCS chooses to monitor only one soil property for soil quality assessment, we recommend measuring total organic C. This research thus provides the guidelines that the NRCS requested with regard to assessing soil quality at the regional scale.
Technical Abstract: The diversity of soil series present in a region may hinder identification of soil quality factors and indicators at a regional scale. Our objectives were: 1) identify soil quality factors for a diverse population of soils at the regional scale, 2) determine which factors vary significantly with land-use, 3) select indicators from these factors that can be used with the NRI for monitoring soil quality, and 4) compare these results to a similar study involving only a single soil series. One hundred and eighty-six points representing 75 soil series in the Northern Mississippi Valley Loess Hills, and 149 points representing 58 soil series in the Palouse and Nez Perce Prairies, were sampled from a statistically representative subset of National Resource Inventory (NRI) sample points and analyzed for twenty soil attributes. Factor analysis was used to identify soil quality factors, and discriminant analysis was used to identify the factors and indicators most sensitive to land-use within each region. In the Northern Mississippi Valley Loess Hills, five soil quality factors were identified. Discriminant analysis selected potentially mineralizable nitrogen (PMN), microbial biomass carbon (MBC), water stable aggregates (WSA), and total organic C (TOC) as the most discriminating attributes between land-uses. In the Palouse and Nez Perce Prairies, six factors were identified. Discriminant analysis selected TOC and total N as the most discriminating attributes between land-uses. The soil quality factors were similar between three of the four regions, but TOC was the only indicator common to all regions for distinguishing between land-uses.