Stacking mitigations to reduce N losses at farmlet scale: Year one results of farm performance in a dairy systems comparison in Canterbury

Abstract

To meet regulatory targets for nitrogen (N) losses, farmers may need to adopt multiple mitigations. Here, we describe the first lactation season (2023-24) of a multi-year farmlet trial that evaluates the effects of ‘stacked’ complementary mitigations on milk production, N leaching, and profitability in a Canterbury farm system. The farmlet trial involved two non-replicated ~12 ha milking platforms and consisted of a 'Control' farmlet following current best practice, and a 'Stacked' farmlet incorporating a multi-species pasture, reduced N fertiliser, and lower stocking rate. Farm physical results were modelled in FARMAX Dairy and OverseerFM to evaluate financial and environmental performance. Milksolids per cow were similar, but production per hectare was 7% lower for the Stacked farmlet relative to the Control farmlet. The Stacked farmlet produced 5% less total pasture (t DM/ha) and differed in seasonal growth. Predicted N leaching (kg/ha) and greenhouse gas (GHG) emissions (kg CO₂e/ha) were 39% and 12% lower, respectively, for the Stacked farmlet, but it also had 8% less profit per hectare due to lower milk revenue and higher costs for pasture conservation and regrassing. Opportunities to improve profitability while maintaining environmental benefits for the Stacked farmlet are discussed.