Submitted to: Proceedings of the TMDL Science Issues Conference
Publication Type: Proceedings
Publication Acceptance Date: 4/25/2001
Publication Date: N/A
Technical Abstract: Implementation of best management practices (BMP's) to reduce the impact of nonpoint source pollution has produced a variety of results. Since water is the primary factor affected by BMP's and the transport mechanisms for materials leached through the soil profile or transported via surface runoff it is necessary to understand the role of BMP's on soil water. Nonpoint source pollution includes nutrients, pesticides, sediment, and pathogens and each behave differently in the soil profile. There is ample evidence in the literature regarded the effect of different management practices on potential nonpoint source pollution. What is lacking is an understanding of the variation that exists within and among agricultural watersheds. Nitrogen and phosphorus represent compounds that behave differently in the soil profile and would require different BMP's to achieve a desired level of reduction. Soil water use rates vary with soil types (soil water holding capacity) and management inputs (nitrogen) and produce different yields. An example for a field in central Iowa reveals that changing N management to achieve a water quality goal will require a detailed understanding of the position on the landscape and conditions for the given year. Water quality improvements are possible through watershed based BMP's that account for the specific conditions within each watershed.