Production, profit and nitrogen flows in irrigated dairy systems representing different industry development pathways: the Pastoral 21 experience in Canterbury

ABSTRACT

Future development pathways for irrigated dairy farms in Canterbury operating under stricter nitrogen (N) loss limits were compared in two farmlets over four years. One represented the traditional pathway of intensification via higher inputs of N fertiliser and supplementary feed (‘higher input-high efficiency’, HI-HE), while the other represented a lower input pathway using half the amount of N fertiliser and one quarter the amount of supplementary feed (‘lower input-high efficiency’, LI-HE). The stocking rate of both systems was matched to feed supply to achieve high utilisation (∼90%) of the pasture grown. Mean total annual N surplus and estimated nitrate-N leaching were lower in LI-HE than HI-HE, by 46% and 25% respectively. Milk production was lower for LI-HE (1,700 kg versus 2,240 kg milk fat + protein per ha/year). Estimated profit was the same for both systems at a milk price of $6.46/kg fat + protein, below which LI-HE was more profitable than HI-HE and vice-versa. Compared with the benchmark high-performing Lincoln University Demonstration Dairy Farm (LUDF) through the same period, LI-HE was 2% less profitable, but estimated N leaching was ∼30% lower. Subsequent adoption of the LI-HE system by LUDF demonstrated that the system is scalable, and profitable.

KEYWORDS:

• Dairy systems
• environment
• nitrate leaching
• nitrogen surplus
• milk production

Acknowledgements

We thank farm staff at the Lincoln University Research Dairy Farm for the management of the experimental herds; the DairyNZ and Lincoln University technical teams for data collection and management; Alan Davie-Martin, Leighton Parker and Garth Campbell for their practical perspectives and advice on systems management; and SIDDC/LUDF, especially Ron Pellow and Peter Hancox, for accepting the challenge of implementing the findings of this work at commercial scale and sharing their experiences and data.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was conducted through the Pastoral 21 Environment Programme (P21 Phase II, C10X1117), jointly funded by DairyNZ Inc., Fonterra Co-operative Group, and the Ministry of Business, Innovation and Employment. New Zealand Ministry of Business Innovation and Employment.