Table 1.

Efficacy ranges (combining plot or field scale empirical data and elicitation of expert judgement) for reductions in nutrient and sediment loss at plot or field scale for a range of mitigation measures targeting both riparian management and farming activities in the wider catchment.

Mitigation measure	Efficacy ranges for pollutant reductions
	Nitrate	Soluble reactive phosphorus	Sediment
Riparian relevant measures
Locate out-wintered stock away from watercourses	0–10	0–10	0–10
Establish and maintain artificial wetlands - steading runoff	10–50	25–80
Site solid manure heaps away from watercourses/field drains	2–25	2–25
Establish 6 m riparian grass buffer strips	−30–95	−83–95	2–98
Measures for wider catchment
Farm track management	0–10	0–10	0–10
Reduce field stocking rates when soils are wet	2–25	2–25	2–25
Move feeders at regular intervals	2–25	2–25	2–25
Establish cover crops in the autumn	25–80	25–80	50–95
Fertiliser spreader calibration	0–10	0–10
Do not apply manufactured fertiliser to high-risk areas	2–25	10–50
Increase the capacity of farm slurry stores to improve timing of slurry applications	2–25	2–25
Do not apply P fertilisers to high P index soils		10–50
Loosen compacted soil layers in grass fields	10–50	10–50	10–50
Allow grassland field drainage systems to deteriorate	0–10	0–10	0–10
Re-site gateways away from high risk areas	2–25	2–25	2–25

Gaps indicate mitigation measure does not impact on the pollutant; – indicates risk of increased losses.