Nutrient loads from agricultural and forested areas in Finland from 1981 up to 2010—can the efficiency of undertaken water protection measures seen?

Long-term data from a network of intensively monitored research catchments in Finland was analysed. We studied temporal (1981–2010) and spatial variability in nitrogen (N) and phosphorus (P), from 1987 losses, both from agricultural and forestry land. Based on trend analysis, total nitrogen (TN) concentrations increased in two of the four agricultural sites and in most of the forested sites. In agricultural catchments, the total phosphorus (TP) trends were decreasing in two of the four catchments studied. Dissolved P (DRP) concentrations increased in two catchments and decreased in one. The increase in DRP concentration can be a result of reducing erosion by increased non-plough cultivation and direct sowing. In forested catchments, the TP trends in 1987–2011 were significantly decreasing in three of the six catchments, while DRP concentrations decreased significantly in all sites. At the same time, P fertilisation in Finnish forests has decreased significantly, thus contributing to these changes. The mean annual specific loss for agricultural land was on average 15.5 kg ha⁻¹ year⁻¹ for N and 1.1 kg ha⁻¹ year⁻¹ for P. In the national scale, total TN loading from agriculture varied between 34,000–37,000 t year⁻¹ and total P loading 2400–2700 t year⁻¹. These new load estimates are of the same order than those reported earlier, emphasising the need for more efforts with wide-ranging and carefully targeted implementation of water protection measures.