FA3 Fertilizer use

>> Background information

Development

Total sales of fertilizers increased rather steadily throughout the 1980s. After reaching a peak in 1990 the sales have begun to fall. Between 1990 and 2010 the total amount of fertilizers sold per arable area fell by approximately 55%. The use of supplementary phosphorus has decreased proportionally the most (over 80%) while the use nitrogen has decreased less (35%).

The use of fertilizers has become more effective during the past twenty years. This can be seen in nutrient balances, which have fallen clearly. Besides resulting from the decease in the use of fertilizers and manure on fields, this is also a result of the increase in crop yield and uptake of nutrients from the soil.

By the beginnig of the 21st century nitrogen balance in Finland was less than 50 kilograms per hectare, which is near the European average. The balance remains much lower in grain growing than in livestock farming where it would seem to be possible to use nitrogen even more effectively.

Phophorus balance has been markedly lower throughout the monitoring period. It has also decreased faster than nitrogen balance: by 85% between 1985 and 2010. The decrease is almost entirely due to decreasing amounts fertilizers used on fields.

Impact on biodiversity

Use of fertilizers has a significant impact on the diversity of farmland species. Fertilization of fields increases nutrient level on the field margins which, in consequence, become eutrophic and poorer in plant species diversity. The invertebrates living on fields are affected more indirectly as fertilization changes the density of plants and the amount of weeds. This leads to changes in the availability of suitable food sources. Species that depend on crop species become more abundant with increasing fertilization because crop species succeed better.

Excessive use of fertilizers combined with small amount of organic matter weakens the activity of soil microbe community. Nitrogen fertilizers also lower the soil pH, which may harm some of the soil organisms. Phosphorus is effectively bound to the typically acidic soils of Finland. Where field fertilization has continued for decades the amount of soluble phosphorus in the soil has increased as well.

Fertilization affects the state of water habitats in whole the catchment area. On areas under intensive agriculture the leaching of nutrients from fields is the main cause of eutrophication in waters (see IW1 and IW2). Efforts to prevent this include more effective use of fertilizers on fields and also the increase in the amount and area of buffer strips, which bound nutrients. Buffer strips and field edges are covered with vegetation all year round and work effectively against soil erosion by preventing nutrients and sediments from leaching.

Requirements of the agri-environmental aid (FA17) include several conditions on the use of fertilizers. Basic measures obligate farmers to follow fertilizer levels that are specified for each crop species. The edges of main ditches and buffer strips near water bodies should not be fertilized. In addition, in traditional biotopes and habitats with high biodiversity value the use of fertilizers is forbidden.