A Soil Quality Framework for Evaluating the Impact of CRP

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The book entitled Soil and Water Quality: An Agenda for Agriculture by the U.S. National Academy of Sciences caused people to ask whether soil quality assessments could be used to evaluate the impact of public policies such as the Conservation Reserve Program (CRP). However, differences in scale, perception of soil quality, and the inability to directly measure soil quality led to significant uncertainty among several potential users. A major challenge was determining how to evaluate and combine information from different indicators to make an overall soil quality assessment that is meaningful. Our objectives are to present a structured approach for interpreting soil quality indicator data and to introduce a conceptual framework that can be used to link the various scales of evaluation, including those needed for assessing effectiveness of public policies such as the CRP. The framework and its use are discussed and demonstrated using soil quality indicator data from published and unpublished studies. On-farm measurements suggest that biological indicators such as microbial biomass and respiration were affected most quickly and to the greatest extent when cultivated land was converted to grassland. Applying the conceptual framework to this data suggests that enrolling fragile lands into CRP had a positive soil quality effect. It also indicates that using no-till practices to return CRP land to row-crop production will preserve soil quality benefits of the CRP, but tilling to prepare a seedbed will destroy the benefits almost immediately.