Denmark was the first country to introduce obligatory fertiliser accounts for all farms in 1987. In 1993 legally binding nitrogen norms were introduced in order to reduce the use of mineral fertiliser. The suboptimal nitrogen norms were introduced in 1998 and this has lowered the N-application 10% to 20% under the optimum for several years. The sub optimal norms have led to lower yields and lower protein content and the economic consequences have been discussed over many years. Following the Food and Agricultural package from 2015 the N-norms were, over a two year period, increased to the economic optimal level in 2017. This has given a unique possibility to compare expected yield changes with actual yield changes 2016-2019 compared to the yield in 2013-2015 in order to estimate the yield increase from higher norms. The findings suggest that the actual yield loss from lower norms has been a little higher than expected based on trials. The increase in yields after the increase in application has been around 2-3 HKg/ha (4%) for wheat and barley and the protein increase has been 0.8-1.0% units for the same crops. The costs of lower norms are estimated to have been around 460-900 million DKK per year for a 16-19% norm reduction.
