This review provides a critical overview of conservation practices that are aimed at improving water quality by retaining phosphorus (P) downstream of runoff genesis. The review is structured around specific downstream practices that are prevalent in various parts of the United States. Specific practices that we discuss include the use of controlled drainage, chemical treatment of waters and soils, receiving ditch management, and wetlands. The review also focuses on the specific hydrology and biogeochemistry associated with each of those practices. The practices are structured sequentially along flowpaths as you move through the landscape, from the edge-of-field, to adjacent aquatic systems, and ultimately to downstream P retention. Often practices are region specific based on geology, cropping practices, and specific P related problems and thus require a right practice, and right place mentality to management. Each practice has fundamental P transport and retention processes by systems that can be optimized by management with the goal of reducing downstream P loading after P has left agricultural fields. The management of P requires a system-wide assessment of the stability of P in different biogeochemical forms (particulate vs. dissolved, organic vs. inorganic), in different storage pools (soil, sediment, streams etc.), and under varying biogeochemical and hydrological conditions that act to convert P from one form to another and promote its retention in or transport out of different landscape components. There is significant potential of hierarchically placing practices in the agricultural landscape and enhancing the associated P mitigation. But an understanding is needed of short- and long-term P retention mechanisms within a certain practice and incorporating maintenance schedules if necessary to improve P retention times and minimize exceeding retention capacity.
Bibliographical noteFunding Information:
Environmental Defense Fund (EDF) organized a workshop in July 2011 on “ Increasing the Assimilative Capacity of Agricultural Landscapes ”. The workshop brought together experts from multiple backgrounds studying the movement, transformation and storage of P. The authors would gratefully acknowledge funding from the Joyce Foundation for associated costs of the workshop. Robbie Kröger would like to acknowledge the Mississippi Agricultural Forestry Experiment Station and the Forest and Wildlife Research Center for support.
- Aquatic system
- Best management practice