Assessing the effect of management intensive grazing on water quality in the northeast US

Stocking rate is the key determining effect of management intensive grazing on dairy farm profitability. However, increased stocking rate can increase NO3- leaching from pastures. Increasing stocking rate increases NO3- loss through leaching because the bulk of the N consumed by the animal is excret ed in concentrated areas of the pasture mainly in urine. We used experiment al data from the northeast U.S. and the literature to assess the relationsh ips between stocking rate and NO3- leaching losses beneath an intensively g razed pasture. A relatively low cumulative seasonal stocking rate of about 200 mature Holstein ha(-1) could result in a 10 mg l(-1) NO3-N concentratio n in the leachate beneath a fertilized, intensively grazed pasture. This me ans that while management intensive grazing can improve farm profitability and help control erosion, it can have a significant negative effect on wate r quality beneath pastures. The extent to which this effect occurs within s pecific watersheds needs to be evaluated in context of the other cropping s ystems and land uses within the watershed.