Epsilon Archive for Student Projects

Abstract

Yesterdays common fertilizing strategy was to apply phosphor (P) and potassium (K) in the
fall a few times in the crop rotation. In the spring only nitrogen (N) was applied. Recent trials
and studies has shown that this strategy, N+P/PK, is ineffective compared with the system
where NPK is spread every year in the spring. The strategy with annual NPK-fertilizer in the
spring has proven to be better for the crop, the environment and the farmers economy.

In the NPK-system the crop responds with higher yields and better quality, especially in the
spring cereals. This is mainly because of an interaction between the different nutrients in the
fertilizer. Phosphorus increase the crops nitrogen efficiency and potassium increase the
phosfor efficiency.

Leakage of phosphor must be reduced in order to prevent the ongoing eutrofication of lakes,
seas and streams. When applying phosphor in the fall the risk for leakage is greater than if it is
applied in the spring. The NPK-strategy therefore means less impact on the environment and
better economy because the phosphor stays in the soil available for the crop.

NPK-products are more expensive than single fertilizers. Because of this it is often said that
the system with annual NPK-fertilizing is more expensive. But when calculating over the
entire crop rotation the result is in favour of the NPK-system. This is due to the even more
expensive PK-products which are used in the N+PK-system. The N+PK-system also means
more applications of fertilizer when spreading P/PK in the fall and the result is additional
costs for fuel and labour. The higher yields and improved quality that is often observed in the
NPK-system is also beneficial.