Nitrogen leaching from agricultural land in Sweden - Model calculated effects of measures to reduce leaching loads

The aim of the calculations in this paper was,) to estimate the effect of m easures to reduce nitrogen leaching from arable land and ii) to estimate wh at reduction in the gross load from southern Sweden could be expected. The measures taken were i) cultivation of a catch crop in spring cereals; ii) s maller applications of fertilizer-N to crops in cultivation systems without manure; iii) spring application of manure and a smaller amount of compleme ntary fertilizer-N; and iv) a catch crop in combination with spring applica tion of manure and a reduced rate of fertilizer-N. The models used were the mechanistic SOIL/SOILN models describing water, heat, and nitrogen flows i n the soil profile. The largest reduction in leaching was obtained with the combination of catch crop, spring application of manure and reduced rate o f fertilizer-N. Total gross load decreased with 16% in this scenario. The c atch crop scenario reduced gross load by a mere 5% because it was only intr oduced in 30% of the acreage of spring cereals. The scenario with a 10% red uction in fertilizer-N resulted in a decrease in load of about 6000 tonnes, i.e. 11%, as well as a yield decrease of about 10%.