March 23, 2011
Last week saw a focus in Washington D.C. on the Chesapeake Bay Region’s water quality and agriculture. On Tuesday, March 15, USDA’s Natural Resources Conservation Service (NRCS) released a report entitled Assessment of the Effects of Conservation Practices on Cultivated Cropland in the Chesapeake Bay Region. The report is one a series of regional assessments included in the NRCS nationwide Conservation Effects Assessment Project.
The Assessment focuses on the 10-percent of land in the 68,500 sq. mile Chesapeake Bay watershed that is cultivated cropland. For purposes of the assessment, cultivated cropland includes land in row crops or close grown-crops, hay and pasture in rotation with row crops or close grown crops, and land in long-term conserving cover under the Conservation Reserve Program (CRP) General Signup. Farmland in hay, pasture, or horticulture for more than 4 or more consecutive years was not included in the assessment.
The Assessment addresses the role played by on-farm conservation practices in reducing pesticide, sediment and nutrient (nitrogen and phosphorus) loading into the Bay’s watersheds. It should be emphasized that the Assessment is not a complete accounting of the disposition of the total nutrients generated by poultry, dairy and other livestock produced in the watershed. Many of the livestock and poultry are fed grain that is imported into the watershed from as far away as Iowa. One estimate has concluded that only 25 percent of the nutrients in the grain is taken up by the animals. The remaining nutrients are contained in manure and poultry litter, much of which is stockpiled and land-applied in the watershed.
The NRCS Chesapeake Bay Assessment is based on 771 sample points that represent the diversity of soils and other conditions in the watershed for cropped acres and an additional 61 sample points for land in the CRP. Farmers at these sample points were surveyed during 2003-2006 to determine their farming practices and on-farm conservation practices at the sample sites. Field level effects of the conservation practices were accessed using a field-scale physical process model. The modeling compared the levels of sediment, nutrient, and pesticide loading with conservation practices to the levels in an alternative “no conservation practice” scenario. A watershed model and database were then applied to simulate how reductions of field losses could reduce in-stream concentrations and loadings of sediment, nutrients, and pesticides in the Chesapeake Bay Region.
Overall, the Chesapeake Bay Assessment indicates that farmers in the region help reduce sediment, nutrient, and pesticide losses from cultivated farm fields with conservation practices, but it is a mixed record. The Assessment found that 19-percent of the cropped acres have a high level of need for additional conservation treatment and 61-percent of the acres have a moderate level of need for additional conservation treatment.
The Assessment also indicated that only about 9-percent of the cropland acres meet full nutrient management criteria for both phosphorus and nitrogen management. Almost none of the cultivated cropland acres receiving manure had consistent use of appropriate rates, timing, and method of manure application on each crop in every year of production.
The Assessment also revealed that the most critical need in the Chesapeake Bay Region is for the control of nitrogen losses through subsurface flow. The use of conservation practices that address only surface nutrient loss and soil erosion can exacerbate subsurface nitrogen losses. As with the CEAP assessment for the Upper Mississippi River Basin, the Chesapeake Assessment recommends that a suite of practices for soil erosion and comprehensive surface and subsurface control of nutrient losses should be implemented, with the rate, form, timing and method of nutrient application addressed in the practices.
Categories: Conservation, Energy & Environment