IMMAG - Iowa Manure Management Action Group

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Updated yields for use in Revised Universal Soil Loss Equation Version 2

Revised Universal Soil Loss Equation Version 2 (RUSLE2) requires a crop yield be entered to provide estimated soil loss and Soil Condition Index (SCI) calculations. These calculations are very sensitive to yield changes. In order to be consistent across the state it is important that a consistent process for determining these yields be used, especially when specific program eligibility is dependent upon the RUSLE2/SCI results.

In Iowa it has been established that the yield for the Soil Map Unit (SMU) used in RUSLE2 is based on the yield from the SMU as taken from the official county soil survey as posted on the Field Office Technical Guide (FOTG). The FOTG yields have recently been updated in all counties. This update uses a methodology for using the Corn Suitability Rating (CSR) by SMU and National Agricultural Statistic Service (NASS) yield data for the various crops the last 5 years. It provides a much more consistent and up to date yields by SMU than previous used in RUSLE2 calculations. Effective immediately the revised county crop yields by SMU are to be used for all RUSLE2 calculations. These revised yields will not be uploaded into the Soil Data Mart until April. In the interim, download and print the revised yields by going to the eFOTG (http://efotg.nrcs.usda.gov/treemenuFS.aspx) and clicking on Section II, Soils Information, Soil Survey Area, and selecting your county. Once you select the county click on Soils Tables and the file "CSRs and Non-Irrigated Row Crop Yields by Map".