Productivity of low-emission systems of pasture-based milk production

Minimizing the use of artificial fertilizer nitrogen (AFN) and optimizing conditions for biologically fixed nitrogen (BFN) in association with clover is a cost-effective strategy for lowering emissions from dairy farms. The objectives of the present study were to examine the productivity of clover-BFN-grassland for pasture and milk production, to quantify the BFN that underpinned this productivity, spring growth and the length of the growing season, nutritive value of pasture at different stages of the growing season and feed budgets. Data were collected from systems-scale experiments at Solohead Research Farm Co., Tipperary, Ireland (52°51′N, 08°21′W). There were 3 systems that had an average of 27 cows per system per year and an average stocking rate of 2.53 cows ha −1 . The intensive control (INT) included average annual AFN input of 265 kg ha −1 , the average clover content of herbage DM was 110 g kg −1 , and slurry was applied by splash plate. The BPN included average annual AFN input of 99 kg ha −1 , clover content averaged 230 g kg −1 and slurry was applied by trailing shoe. Best practices including AFN (BPO) received minimal (