Dissolved Phosphorus Contributions From a Southern Minnesota Saturated Buffer Field Site: Agricultural Best Management Practices and Dissolved Phosphorus Loss

Phosphorus is a growing water quality concern in agricultural landscapes. Sources of agricultural phosphorus include synthetic fertilizers and manure application that support crop growth. These sources lead to excess phosphorus in adjacent waterways causing harm to aquatic communities and to human health. Phosphorus is transported downstream contributing to larger pollution issues including the “dead zone” in the Gulf of Mexico. Conservation practices called Best Management Practices (BMPs) have been developed to manage agricultural phosphorus pollution. One common BMP is a riparian, or streamside, buffer. This BMP allows for the reestablishment of vegetation between an agricultural field and adjacent waterway. Riparian buffers act as a filter strip and are effective for nitrogen, sedimentation, and erosion control. The efficacy of these practices to manage phosphorus, however, is less clear, notably regarding dissolved phosphorus. Dissolved phosphorus is highly bioavailable and ready for plant uptake, contributing to pollution from rapid algae growth. A saturated buffer is a specific type of riparian buffer known to be effective for nitrogen and particulate phosphorus removal, but in some cases has been shown to contribute to dissolved reactive phosphorus (DRP) pollution. Through field data collection, the aim of this case study is to document DRP contributions from a saturated buffer field research site located in Southern Minnesota. In addition, this study documents the drivers of DRP contributions including soil characteristics, microbial community structure, and flooding. Results from the work demonstrate the need to account for dissolved phosphorus in meeting water quality goals through the implementation of agricultural BMPs.