New Zealand dairy farm system solutions that balance reductions in nitrogen leaching with profitability – a case study

Abstract

ABSTRACT This study tested prescribed management practices to reduce nitrogen (N) leaching by 20% while maintaining or improving profitability relative to an existing farm management baseline (Control). N leaching and profitability were estimated for a South Canterbury case study dairy farm using Overseer® Nutrient Budgets and FARMAX Dairy. Three practices were used: (1) reducing N in cows’ diets through low-N feed (fodder beet), (2) recapturing N from soils through catch crops (oats) and (3) diluting urinary N by including plantain in cows’ diet. While most treatments reduced N leaching, significant management inputs were required to achieve a 20% reduction from the Control. Plantain was identified as the key forage for reducing N leaching from the milking platform. Fodder beet and oats had little impact, due to the small area cropped on the milking platform and low dietary substitution. However, they increased profitability relative to the Control. Only one scenario, employing all three forages with biannual direct drilling of plantain, achieved the target, reducing N leaching by 27% and increasing profitability by 2% compared with the Control. The implications of this modelling study for real-life application are that a combination of measures will be needed to achieve large environmental and economic targets.