The Iowa Department of Natural Resources and the Iowa Finance Authority have developed clean water state revolving fund-linked deposit loan programs for manure management and soil erosion control. Working with the soil and water conservation districts in the state to identify farmers and others with eligible needs, the state uses its Clean Water State Revolving Loan Funds (SRF) to reduce interest rates for landowners that are making changes to address these nonpoint sources.
A brief case study of this is available here.