Productivity and N-leaching in organic dairy grass-arable crop rotations

Summary

Due to increasing size of Danish organic dairy farms uniform grazing of all cropped land becomes inexpedient due to long distance to the milking facilities. We investigated nutrient dynamics and feed production in two dairy crop rotations with internal differences in proportion of grazing and cutting. One six year crop rotation represents close to the farm buildings (barley [Hordeum vulgare L.] undersown with grass-clover [Lolium perenne L.–Trifolium repens L.] - 4 years of grass-clover - spring barley/catch crop) and another represents further away (barley undersown with grass-clover, 2 years of grass-clover -barley/catch crop - maize [Zea mays L.]/catch crop - lupin [Lupinus angustifolius]/catch crop). In each of the crop rotations was made five treatments concerning grazing/cutting strategy and manure application. Results from the first experimental year shows that herbage production was high in year 1-4 of grass-clover. Nitrate leaching in the crop rotations were highest in grazed and manured 2-4 years old grasslands, but also following maize and lupin considerable losses occurred despite the presence of catch crops. Following grassland cultivation, a barley silage crop undersown with Italian ryegrass [Lolium multiflorum L.] reduced leaching to a minimum.