By Sirkka Tattari and Markku Puustinen, Finnish Environment
Institute The mitigation measures decreasing the runoff of solid
matter and nutrients from field cultivation can be divided into
measures taken on the field, at the edge of the field and
outside the field. As for the measures taken on the fields,
fertilization levels of phosphorus and nitrogen have decreased
significantly. At the same time the total area plowed in autumn
has decreased by half as it has been replaced by reduced tillage
and direct sowing systems. This has been shown to reduce
especially erosion and particulate phosphorus runoff but also
the runoff of total nitrogen. The problems related to dissolved
phosphorus runoff, especially from fields with soils rich in
phosphorus, still call for separate solutions, e.g. reducing the
overall P content of fields. Water sampling in the Aurajoki
river. reduction in nutrient load achieved by buffer zones
depends not only on the extent of the measure itself but also on
the other, on-field measures imp