Wednesday, 12 July 2023 12:55

Reviewing 50 years of NZ use

Written by  Staff Reporters
Even well managed grass/clover pastures remain deficient in nitrogen for much of the year. Even well managed grass/clover pastures remain deficient in nitrogen for much of the year.

Nitrogen is an essential nutrient for plant growth, and nitrogen fertiliser has long been critical to maintaining the high productivity of grazed pasture systems in New Zealand.

For several decades research has been done on establishing the scientific basis for nitrogen management and fertiliser application in ryegrass and clover pastures. However, with so much research going on across various locations over the years, it hasn't always been easy to step back and see the full picture.

That is what prompted AgResearch senior scientist Dr Col Gray, with the backing of the Fertiliser Association of New Zealand, to take a closer look at the research undertaken over the last 50 years. He set out to provide an overview of this research, to raise the awareness of key findings, and importantly to provide a pathway for decision makers to find and access the research on nitrogen fertiliser use and management. Identification of knowledge gaps for new avenues of enquiry was another focus.

The result of this review is now published in the New Zealand Journal of Agricultural Research. The full open access article, Nitrogen fertiliser use in grazed pasture-based systems in New Zealand: a summary, can be viewed at

The key research findings from the paper are as follows:

  • Even well managed grass/clover pastures remain deficient in nitrogen for much of the year. As a result, it has been shown that grass/clover pasture responds readily to the application of nitrogen fertiliser.
  • The response to nitrogen fertiliser application is variable and depends on the rate, timing, carry-over effect of nitrogen fertiliser, and site conditions such as slope, aspect, soil fertility status and pasture composition.
  • The best time of year to apply nitrogen fertiliser to grazed pasture depends on when extra feed is required by the animal, and the ability of the pasture to respond to the application of nitrogen.
  • The response to late winter/early spring application of nitrogen fertiliser is generally higher and more reliable than nitrogen applied in autumn.
  • The application of nitrogen fertiliser can negatively affect the clover content in grass/clover pasture due to reduced stolon number and length, less stolon branching, inhibited biological nitrogen gas fixation, and increased competition for moisture and nutrients by the grass component in the sward. Therefore, a critical management practice to maintain adequate clover is tight grazing to control pasture cover, particularly in the spring.
  • Nitrogen derived from the application of fertiliser can be lost directly or indirectly (nitrogen excreted from animals) from soils under grazed pasture through nitrate leaching, ammonia volatilisation and nitrous oxide from denitrification.
  • Direct leaching from the application of nitrogen fertiliser is low if application rates are not excessive and are synchronised with active growth of the pasture.
  • Urine excreted by animals is the main factor affecting nitrate leaching losses.
  • Ammonia volatilisation losses from fertiliser are typically less than 15% of the nitrogen applied, while emissions of nitrous oxide from nitrogen fertiliser are approximately 4% of total agricultural emissions in New Zealand.
  • New technologies such as coated nitrogen fertiliser products, plant growth regulators, advances in precision agriculture and digital technologies have potential to be applied to grazed pasture systems to optimise nitrogn fertiliser use and minimise environmental impacts.

The review concludes: "With increasing expectations from consumers and constraints by regulators on the impact of using nitrogen fertiliser, it is likely there will still need to be innovation in the future to develop new nitrogen fertiliser products and technologies to further minimise environmental impacts and improve the efficiency of nitrogen fertiliser use".

More like this

Finalists named for Primary Industries awards

One of the country’s top trade officials, a respected farmer and orchardist and a radio presenter are in the running for the 2024 Outstanding Contribution to New Zealand's Primary Industries award.

'Living labs' to tackle emissions

Living labs that bring together expertise at locations around New Zealand are among potential solutions identified by researchers to help the country move towards a more climate resilient future.

Meat wellness, well done

Newly published research shows overseas consumers have a strong interest in improving their wellbeing through eating red meat, highlighting opportunities to achieve a premium for products with proven health benefits.


Editorial: Fonterra's U-turn

OPINION: Speaking at the Chinese Business Summit in Auckland last week, Fonterra chief exuecutive Miles Hurrell revealed that his phone was running hot over the weekend.

A winner's view

Kingi Smiler, the chair of Wairarapa Moana ki Pouakani (WMI), said after winning the Ahuwhenua Trophy he was both elated and relieved and added it was a tough competition being up against Whakatohera Māori Board.

Farm 4 is number one!

A dairy farm near the settlement of Mangakino has won the prestigious Ahuwhenua Trophy for the top Māori dairy farm for 2024.


A good start

The final Global Dairy Trade (GDT) auction for the 2023-24 season augurs well the forecast milk price for the new…

Labour eyes rural votes

Labour Party agriculture spokesperson Jo Luxton is on a mission to win back rural sector votes.

Machinery & Products

Tractor, harvester IT comes of age

Over the last halfdecade, digital technology has appeared to be the “must-have” for tractor and machinery companies, who believe that…

» Latest Print Issues Online

Milking It

Well done Kotahi!

OPINION: Fonterra's decision to join forces with other primary sector exporters and launch a supply chain collaboration, Kotahi, is paying…

» Connect with Dairy News

» eNewsletter

Subscribe to our weekly newsletter