The purpose of the National Assessment for Cropland is to estimate the environmental benefits and effects of conservation practices applied to cultivated cropland and cropland enrolled in long-term conserving cover (e.g. the Conservation Reserve Program).
The Cropland Component of the National Assessment has three specific goals:
Estimate the effects of conservation practices currently present on the landscape.
Estimate the need for conservation practices and the potential benefits of additional conservation treatment.
Simulate alternative options for implementing conservation programs on cropland in the future.
The ultimate goal of the Cropland Component is to report conservation effects in terms that represent recognizable outcomes, such as cleaner water and soil quality enhancements that will result in more sustainable and profitable production over time.
The Cropland Component uses a sampling and modeling approach to estimate the benefits of conservation practices. The approach consists of four basic steps or activities:
First, a subset of National Resources Inventory (NRI) sample points has been selected to serve as "representative fields." These NRI sample points, which are located on cultivated cropland and land in long-term conserving cover, provide the statistical framework for the model as well as information on soils, climate, and topography.
Second, USDA developed and implemented the CEAP Cropland Farmer Surveys to collect the information needed at the selected NRI sample points to run field-level process models and assess the effects of conservation practices. The National Agricultural Statistics Service (NASS) interviews cooperating farmers to obtain current information on farming practices (crops grown, tillage practices, nutrient and pesticide application, conservation practices, etc.)
Third, USDA will use the physical process model called APEX (Agricultural Policy Environmental Extender) to estimate field-level benefits. APEX is a variant of the EPIC (Erosion Productivity Impact Calculator) model that allows us to estimate the effects of buffers, grassed waterways, and other erosion control practices. APEX allows estimation of the reductions in soil loss, reductions in nitrogen loss, reductions in phosphorus loss, and reductions in pesticide loss from farm fields. Pesticide loss will be expressed as reductions in pesticide risk. APEX also allows us to evaluate soil quality enhancement as a result of practice implementation.
And finally, CEAP is integrating the model output from APEX with another model called SWAT/HUMUS (Soil and Water Assessment Tool / Hydrologic Unit Model of the United States) to assess off-site benefits for water quality and availability. HUMUS includes databases on land use and sources of non-point and point source pollutants that are used with the SWAT model to simulate the transport of water and potential pollutants from the land to receiving streams, and routes the flow downstream to the next watershed and ultimately to the estuaries and oceans. SWAT/HUMUS allows estimation of the reduction in in-stream concentrations of sediment, nutrients, and pesticides attributable to implementation of conservation practices.
The CEAP Cropland National Assessment is a collaborative effort led by NRCS in partnership with USDA's Agricultural Research Service and Texas Agri-Life Research of Texas A&M University. USDA's National Agricultural Statistics Service and Farm Service Agency also contribute.
The findings of the CEAP Watershed Assessment studies will be used to refine the methods and models used in the National Assessment to better simulate and estimate the effects of conservation practices. CEAP Watershed Assessment findings will also be used to verify relative trends in results from the regional Cropland National Assessments. Formerly cropped wetlands are addressed within the scope of the CEAP Wetlands National Assessment. The effects of cropland conservation practices on wildlife or aquatic species are addressed within the scope of the CEAP Wildlife National Assessment and in some CEAP Watershed Assessment Studies.
River Basin Cropland Modeling Study Reports.
This series of reports assess the effects of conservation practices on cultivated cropland (in 2003-06), including land in long-term conserving cover.