The Nutrient Export Risk Matrix (NERM) for strategic application of biosolids to agricultural land

Diffuse phosphorus (P) export from biosolids application to agricult­ ural land above specified soil P thresholds or incidental losses of nutrients applied as manure or fertilizers during high risk periods, may be linked to deteriorating surface or groundwater quality. However, oui research suggests that not all land has an equal risk of contributing diffuse contaminants to receiving waters, either via surface or groundwater delivery routes, and that high risk is associated with critical source areas of diffuse pollution where source and transport risks coincide. We report the initial output from a res­ earch programme examining the environmental risk of biosolids recycling to agricultural land, which is being synthesized into a risk advice matrix: the Nutrient Export Risk Matrix or NERM for end-users in the water industry. The intention is that the NERM will help determine the most appropriate form and frequency of spatially-sensitive biosolids application to land to achieve sustainable biosolids management without detriment to the environment and receiving water quality, whilst being of net benefit to land managers.