In areas with animal production, proper manure handling is a key measure to reduce pollution.
Soil phosphorus content (measured as P-AL) is often very high in areas with intensive animal production, due to the addition of large amounts of manure (often in combination with mineral fertilizers) over a long time. Hence, large amounts of nutrients can be added to waterways through runoff from these areas. A long-term measure in such areas will therefore be to reduce soil phosphorus content by reducing fertilization, improve manure handling, as well as to maintain the requirements for manure per area unit.
The area requirement for manure in Norway is 0.4 hectares per animal unit. These measures will primarily have a significant effect over time, but will also reduce the loss of dissolved nutrients to waterways in the short term. Control of the manure storage is important to avoid leakage into nearby waterways. Furthermore, it is important that the fertilizer planning take sufficient account of the nutrient content in manure, so that the supply of mineral fertilizers can be reduced. Time for spreading of manure is also of great importance. Manure should be primarily spread during the growing season, when the risk of nutrient runoff is relatively low due to less precipitation, higher plant uptake and relatively high evaporation. The risk of runoff of nutrients is greatest when the manure is spread during periods of heavy runoff outside the growing season.
Sedimentation ponds with vegetation filters have proven to be effective as secondary measures in livestock regions in the south-west of Norway, primarily due to retention of particles and particle-bound phosphorus. The ponds have generally less effect on the retention of nitrogen.
Other important measures are unfertilized buffer zones between pastures and waterways, and permanent vegetation zones between open fields and rivers.