Integrated forage system reduces off-farm purchased nitrogen and limit surplus on intensive dairy farms in northern Italy

Intensive dairy farming relies on large inputs of N fertilizer and on the off-farm nitrogen to sustain a high milk output per hectare, which leads to an overuse of N, and to a reduction of Nitrogen Use Efficiency (NUE). This multiyear study aims to verify, through a Living Lab approach, on two commercial dairy farms in the Northern Italy, the effect of planning and managing of a forage system on N balance and NUE. Two periods (3 years each) before and after the changes in the farm and forage management were considered. The introduction of legume crops, double cropping, winter crops, and the adoption of early cutting of forages coupled with an efficient conservation of forages, were adopted on the farms. These actions have improved the uptake potential of the crops and the recycling of N from livestock to the forage system and back again. Changes in forage system management allowed to increase the average dry matter yield and N uptake per hectare on both farms, mainly due to the contribution of alfalfa, Italian ryegrass, and corn harvested as high moisture silage. The N output from cash crops, forages, and N input from nitrogen fertilizers were reduced on both farms, while the input from biological N fixation was increased. This resulted in a reduction of around 30 % of N surplus on the farms, and in a higher N efficiency. This study shows that milk production could be intensified, and nitrogen surplus could be reduced by acting on the management of the forage system and of conservation techniques to improve feed selfsufficiency, and by relying on the introduction of legume crops and on a reduction of off-farm nitrogen, through a synergistic Living Lab approach.