The effect of grass buffer strips on phosphorus dynamics - A critical review and synthesis as a basis for application in agricultural landscapes in France

Recommending the use of "grass buffer strips" to control diffuse P transfer has become well accepted among extension advisors, agricultural consultants, planners, and other practitioners that influence the structure of the agricultural landscape. These grassed areas are put in place to capture the P contained in runoff from source fields. They are designed to function as a filter and a sediment trap although it is often unclear what the long-term disposition of the accumulated P may be. The objective of this work was to determine if the available scientific literature justifies the continued recommendation of this approach in the prevention of phosphorus movement from agricultural soils to surface waters. We employed a theoretical analysis of the mechanisms of the buffering effect and the specific behaviour of phosphorus in typical grass buffer strips to establish the critical set of literature applicable to this question. An adequate body of literature exists describing many aspects of P dynamics and the short-term functioning of grass buffer strips over their seasonal cycles. Despite variable results in a diversity of landscape contexts, overall, the use of grass buffer strips appears to provide useful short-term functions in the reduction of P transport to surface waters. Long-term benefits remain questionable given the relatively short-term use of this approach in P reduction and the lack of long-term experimental results, but this current lack of data is not sufficient to deter the continued incorporation of grass buffer strips in the landscape of French agricultural. Additionally, a more comprehensive conceptual model integrating the short-term functioning of grass buffer strips with seasonal cycles and the long-term consequences of cumulative storage emerged from our synthesis. (c) 2006 Elsevier B.V. All rights reserved.