Duration-controlled grazing of dairy cows. 1: Impacts on pasture growth, cow intakes and nutrient transfer

Abstract

ABSTRACTStanding cows off pasture after 4 hours of grazing (duration-controlled (DC) grazing) was researched over 3 years (2008–2011) to compare the losses of nutrients in drainage and surface runoff water with losses under standard grazing (SG). Pasture growth rates, nutrient concentrations and apparent intake by cows were used to model nutrient removals from, and returns to, pasture. Pre- and post-grazing covers and apparent pasture intakes were similar for both treatments. Quantities of N, P and K returned to the DC plots in excreta and effluent were 34%, 0% and 45% less than those returned to SG plots. This reduction in nutrient returns was associated with a nil, 20% and 9% decrease in annual pasture growth on the DC plots in the three respective years. Reductions in annual pasture growth under DC grazing may be avoidable if nutrient removals are balanced with returns in effluent and fertiliser.