The effect of farm and catchment management on nitrogen transformations and N2O losses from pastoral systems — can we offset the effects of future intensification?

The increased availability of reactive nitrogen (Nr) has led to intensification of animal production systems and consequently to increases in gaseous emissions and N leaching. Current options for reducing the environmental footprint from pastoral systems whilst meeting the growing demand for milk and meat include: nitrification inhibitors that keep N in the less mobile ammonium form for longer period, restricted grazing to minimise the deposition of urine patches to pastures at high-risk times of the year, using maize or cereal silage, and ‘edge-of-field’ attenuation systems. A modelling assessment suggests that these options, alone or in combination, can reduce total losses from current systems. However, these reductions are not likely to offset any increase in losses that may occur under future intensification. Nevertheless, these options are increasing the efficiency of dairy farming systems (reduced N losses per unit of product). The mitigation potential of the current options could be increased by exploiting spatial and temporal variability of N losses. In addition, research should continue to focus on developing new options for improving the efficiency of conversion of N into products, to ensure any gains in efficiency to match the expected rate of productivity increase.

► Current N mitigation options can reduce total N losses from pastoral systems. ► The reductions are not likely to off-set any increase in losses that may occur under future intensification. ► There are no ‘silver bullet’ options and packages of measures are required to make the necessary gains. ► The options are increasing the efficiency of dairy farming systems and can reduce the N losses per unit of milk produced. ► The mitigation potential of the current options could be increased by exploiting spatial and temporal variability of N losses. ► Improved animal and plant interventions for improving the efficiency of conversion of N into products are required, to ensure any gains in efficiency match the expected rate of productivity increase.