We are currently evaluating the effectiveness of grass buffer strips (GBS-eff) for nutrient retention. Today, there are no obligations to cut or remove the grass on GBS which may lead to phosphorus (P) saturation. In the on-going field experiments we are testing if removal (harvesting) the grass can reduce soil P enrichment in GBS and improve and even-out water infiltration, in order to advance sediment and P retention. The ongoing project produces data for 2 years but since weather conditions are highly variable between years more data and evaluations are needed to facilitate good decision-making and calculations of cost-efficiency. In addition, GBS-eff is highly dependent on management of the upstream field. In this new project we will evaluate GBS-eff when the field is fertilized with slurry, which currently is applied to 25 % of Swedish arable soils.