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An Overview of the NRI Soils

An Overview of the NRI

The National Resources Inventory (NRI) is a scientifically credible statistical survey designed to help gauge natural resource status, conditions, and trends on the Nation’s non-Federal land. Non-Federal land—which includes privately owned lands, tribal and trust lands, and lands controlled by State and local governments — represents nearly 75 percent of the Nation’s total land area.

The NRI is conducted by the Natural Resources Conservation Service (NRCS) in cooperation with Iowa State University’s Center for Survey Statistics and Methodology (ISU-CSSM). This partnership ensures that the NRI is science based, employing well-established scientific survey principles.

The NRI is carried out under the authority of a number of legislative acts, including the Rural Development Act of 1972, the Soil and Water Resources Conservation Act of 1977, the Federal Agriculture Improvement and Reform Act of 1996, and the Farm Security and Rural Investment Act of 2002.

Information derived from the NRI is used by natural resource managers; policy makers: analysts; consultants; the media; other Federal agencies; State governments; universities; environmental, commodity, and farm groups; and the public. These constituents use NRI information to formulate effective public policies, fashion agricultural and natural resources legislation, develop State and National conservation programs, allocate USDA financial and technical assistance in addressing natural resource concerns, and enhances the public’s understanding of natural resources and environmental issues.

NRI data are designed to be part of the core components of USDA’s conservation strategic planning and accountability efforts, and to help assess consequences of existing legislative mandates, such as the appraisals required by the Soil and Water Resources Conservation Act (RCA) and the periodic Farm Bills. The 2007 NRI is providing the analytical foundation for the RCA Appraisal that USDA will deliver to Congress by January 2011 and the subsequent update of the National Conservation Program, which together provide guidance to USDA on conservation activities needed to meet the Nation’s long-term resource needs. The NRI will provide a statistical framework to evaluate proposed programs and policies relative to environmental considerations and various climate change scenarios, and relative to short- and long-term productivity and economic considerations.

A Unique Assessment Tool

The NRI provides nationally consistent statistical data that support analysis of resource trends on rural and developed land over all regions of the United States since 1982.

This trending capability is possible because —

  • the same sample sites have been studied since 1982;
  • a number of key data elements have been collected in a consistent manner since 1982;
  • the inventory accounts for 100 percent of the surface area of the United States;
  • quality assurance and statistical procedures are designed to ensure that trend data are scientifically
  • legitimate and unambiguous; and
  • The NRI facilitates the tracking of lands as they go from one land use category to another.
  • The NRI can address a broad range of natural resource issues, enabling it to fulfill its primary purpose of supporting agricultural and environmental policy development and program implementation. Interpretations and analyses are made from a natural resources perspective rather than from a purely land use or vegetative cover or ownership basis because the NRI is soils-based. The NRI has evolved over time; it has adapted to broader and more sophisticated goals, changing technologies, and the need for more cost-effectiveness.

    Progressing to Annual Inventory

    The NRI was conducted every 5 years during the period 1977 to 1997, but is now conducted annually. This shift helps align the NRI with the need for timely information to support agricultural and conservation policy development and the assessment of the impacts of policy choices and conservation program implementation.

    For the Annual NRI, data are gathered for a scientifically selected subset of the 800,000 sample sites that were established for previous NRIs. This subsample includes a set of "core" sample sites, which are sampled each year, and "rotation" (or "supplemental") sample sites that vary by inventory year and allow an inventory to focus on emerging issues. Data collection relies upon high-quality, high-resolution aerial photography, field office records, historical records and data, ancillary materials, and on-site visits.

    NRI data release procedures are affected by implementation of an annual data collection approach because the scale of NRI estimates is affected by reduced sample sizes. Estimates are released on a 5-year cycle, when they meet statistical standards and are scientifically credible in accordance with NRCS policy and with OMB and USDA Quality of Information Guidelines.

    Interpretation of the data

    The NRI provides not only overall estimates of changes in resource conditions but also the dynamics of those changes. For example gross losses and gains in cropland can be examined, and it can be determined why cropland was lost, how much had been classified as prime farmland, and where these losses occurred.

    NRI survey results are based upon a particular set of definitions, protocols, and instructions. These have been developed to support NRCS programs and USDA analytical needs, so they differ in some cases from those used by other agencies. These differences need to be considered when analyzing and interpreting the data.

    Non-Federal Land: Most NRI estimates pertain only to non-Federal rural lands; non-Federal lands include privately owned lands, tribal and trustlands, and lands controlled by State and local governments. Some estimates, such as those for wetlands and deepwater habitats, cover water areas and all non-Federal lands including developed land.

    Soil Erosion: NRI erosion estimates are based upon erosion prediction models rather than on-site measuring of soil detachment, transport, and deposition. The erosion prediction models provide estimated average annual (or expected) rates based upon the cropping practices, management practices, and inherent resource conditions that occur at each NRI sample site. Climatic factors used in the erosion prediction equations (models) are based upon long-term average conditions and not upon one year’s actual events. NRI estimates of sheet and rill erosion utilize standard Universal Soil Loss Equation (USLE) technology rather than revised USLE (RUSLE) methodology so that it is possible to make comparisons back to the year 1982. Erosion estimates are currently made only for cropland, CRP land, and pastureland. Erosion prediction models for rangeland are currently under development and evaluation.

    Developed Land: The NRI category of developed land differs from that used by some other data collection entities. For the NRI, the intent is to identify which lands have been permanently removed from the rural land base, while other studies are interested in human populations (e.g., Census of Population) and housing units (e.g., American Housing Survey). The NRI developed land category includes (a) large tracts of urban and built-up land; (b) small tracts of built-up land of less than 10 acres; and (c) land outside of these builtup areas that is in a rural transportation corridor (roads, railroads, and associated rights-of-way).

    CRP Land: For the NRI, CRP land is classified separately from cropland because it provides different resource and conservation issues than hayland, horticultural cropland, and cultivated cropland. Acres in CRP can be added to NRI cropland acres for analyses and reporting.

    Irrigation: For the NRI, land is considered irrigated if irrigation occurs during the year of inventory, or during 2 or more of the 4 years prior to the inventory. Other entities typically consider land irrigated only if irrigation water is applied for the year of interest.

    Wetlands: NRI classification of wetlands is slightly different than that used by the Fish & Wildlife Service (FWS) in their statistically based Wetlands Status and Trends study. The NRI and the FWS inventory have different legislative mandates; sampling methodology, inventory protocols, data handling, and analysis routines have evolved independently over the past two decades, even though both survey programs use the hierarchical Cowardin classification system. Recent collaborative efforts have resulted in enhanced classifications for both programs, but wetlands data collected by the two agencies are currently neither comparable nor interchangeable. The NRI multiresource approach is beneficial to USDA analysts and others who examine conservation and agrienvironmental issues. Results from the FWS study are beneficial to analysts in the Department of the Interior and others.

    Further information regarding NRI and additional national reports can be obtained from the national NRI Web site at http://www.nrcs.usda.gov/technical/NRI/.

    Last Modified: 08/31/2010