Nitrogen balance as an indicator of nitrogen leaching in Finland

When measured data of nitrogen (N) losses to the environment are not available, calculated N balances are often used to indicate losses. The aim of this study was to describe the relations between N surface balances and N leaching losses in two agricultural runoff fields. Data of runoff fields dominated by cereal and grass production were available for clay soil for 1980–2001 and for sandy soil for 1992–2000. The total sum of N leaching via drainage and surface runoff was 2–40 kg N ha−1 year−1 in the clay soil and 2–104 kg N ha−1 year−1 in the sandy soil. The annual N surface balances were from −44 to 145 kg N ha−1 in the clay soil and from −63 to 417 kg N ha−1 in the sandy soil. The highest annual N leaching losses were usually not caused simply by high N balances, but, rather, were mainly due to poor management. The highest annual N leaching losses occurred in the clay soil from bare fallow and in sandy soil after application of slurry to the frozen soil.