Growing Futures

Reducing nitrogen in the dairy industry

Reducing nitrogen in the dairy industry

Growing maize silage on effluent sites reduces need for nitrogen loss strategies

Dairy is New Zealand’s largest export industry, with annual exports in excess of $13 billion. A key challenge for the dairy industry is managing the large volume of effluent produced by the more than six million cows, in order to maintain the health of water and soil resources whilst remaining competitive in the global marketplace.

Around one million tonnes of maize is grown in New Zealand each year for use by the dairy industry as silage, a stored fodder crop. Growing maize provides cows with a high energy feed during times of low pasture production and is often included in a pasture renewal rotation system. Maize requires key nutrients – nitrogen, phosphorus and potassium – at similar ratios to those found in dairy effluent, and its root structure enables it to use nutrients from areas of the soil deeper than those reached by traditional pasture species.

Research has shown that maize crops grown on farm blocks with long term dairy effluent application require little or no additional fertiliser, reducing the costs of feed production and reducing the need for sometimes costly strategies to reduce nitrogen losses. Earlier research has also shown that supplementing cows’ feed with maize reduces nitrogen leached (per kilogram of milk solids) by 20 to 32% compared to those cows in all grass feed systems.

Producing a maize crop on an effluent block without using fertiliser does not result in a significant difference in yield but can save the farmer $937 per hectare in growing costs. It is estimated that, by 2024, the inclusion of maize in the pasture renewal rotation on dairy effluent areas will have a net annual benefit of $30 million in feed production costs.

The research was funded through the Ministry for Primary Industries’ Sustainable Farming Fund with support from the Foundation for Arable Research, Dairy New Zealand, Environment Waikato and the dairy industry.

Created: September 2014

Share this impact case study: