S F Ledgard1, J Rendel2, S Falconer1, T White1, S Barton3 and M Barton3
1 AgResearch Ruakura Research Centre, Hamilton 3240, New Zealand, [email protected]
2 AgResearch Invermay Research Centre, Mosgiel 9053, New Zealand
3 Farmer, Hingarae Road, R.D. 1 Turangi 3381, New Zealand
Farms in the Lake Taupo catchment of New Zealand have a farm-specific nitrogen (N) leaching limit per hectare. A beef cattle finishing farm in the catchment was used as a case study to compare optimised scenarios with and without N constraints and with flexible supply to meat processing companies or a requirement for regular supply to restaurants based on a premium price for beef with a low N footprint. Scenario analyses included evaluation of sourcing surplus young beef cattle from breeding farms or from dairy farms. A life cycle assessment method was used to estimate all reactive N emissions through the life cycle of beef. Leaching of N from the finishing farm was <20 kg N/ha/year from N-constrained scenarios and 43 kg N/ha/year with no N constraint. Profitability decreased with N constraints and with regular beef supply requirements, which could be countered by a price premium. The N footprint from beef production ranged from 95 to 156 g N/kg meat, being least from the N-constrained scenarios. It was lower from dairy-derived beef and higher with regular beef supply requirements. The farm stage dominated the life-cycle N footprint (78% of total emissions) with the only other significant contributor being the final waste (sewage) stage at 21% of the total, based on a traditional urban waste water treatment system. Preliminary analysis indicated that the Taupo town sewage system of land application to pasture for silage production and feeding back to cattle can further decrease the N footprint over the life cycle of beef.