Government’s freshwater regulations
One of the reasons you may be reviewing your fertiliser use is because of the Government’s 190kg N/ha cap on synthetic nitrogen fertiliser.
Central Government's new freshwater regulations came into force on September 3, 2020. Regional councils are charged with implementing and monitoring the rules. The details on how they plan to do that will become clearer as they work their way through the changes. For more detailed information on all aspects of the regulation click here.
What do I need to do now?
- Understand the new regulations and how they would apply to your farm. Discuss with your trusted advisor or your regional DairyNZ Environmental Change Specialist.
- Know how much synthetic N fertiliser was applied last year over each hectare or paddock of the farm as well as on average over the whole effective pastoral area. It is important to accurately identify the size of the reduction required.
- Have good systems in place for recording the tonnages of all synthetic N fertiliser applied on farm and the area it was applied to for reporting to the regional council. When using a mix of products ensure all sources of synthetic N are accounted for and the application rates.
- Review your current N use strategy to identify potential areas to improve N use efficiency.
- How much N fertiliser was applied and when? Was the N fertiliser applied to the paddocks/areas of the farm targeted? If using contractors check the application tracking data. Some farmers have reported significant discrepancies between planned and actual N use.
- How much N fertiliser was applied on the effluent and non-effluent areas?
- How many applications, how often and at what rate (kg N/ha/application)?
- What type of N fertiliser was used?
- Has the N boosted grass been used to fill a genuine feed deficit?
- Create a plan to meet the 190 kg N/ha cap. If you are currently using more than 190 kg N/ha of synthetic fertiliser over any area of the farm you need to take some actions now to comply with the new requirements. If a significant reduction is required (>50 kg N/ha), targeting half of the required reduction now (2020/21 season) and the other half next season can help ease into the new system with less N fertiliser used. If you will be exceeding the cap from July 2021 you can apply for a resource consent and two options are available for doing so (as described above).
Strategies to reduce N fertiliser use successfully
The following recommendations are based on experiences from Canterbury farmers who have reduced N fertiliser successfully and without compromising pasture harvested or profit. The farmers have been involved with the Forages for Reduced Nitrate Leaching research programme and the Hinds and Selwyn Project. Many of these strategies are supported directly by science and some are based mainly on farmer experience.
Farmers' lessons of what to avoid
- Inadequate and/or inaccurate monitoring and recording of N fertiliser applications leading to higher N used than expected at the end of the season.
- Routinely following each grazing with N fertiliser and not responding to a genuine feed deficit. This can be particularly wasteful if on fast grazing rounds.
- Needing N fertiliser to meet a feed deficit generated by following fast grazing rounds. When grazing on fast rounds (< 21 days) pasture is grazed before the 2½ leaf stage (compared to a longer grazing round and grazing at between 2½ and 3 leaf stage) missing out on the period of highest accumulation of growth. This will result in a lower response rate to N fertiliser.
- Using high N fertiliser rates each time that cannot be fully used by plants increasing the risk of the surplus N being lost from the root zone.
- Inadequate pasture monitoring and recording to inform decision making
- The extra N boosted grass grown is poorly utilised,g. increase in residuals or excessive pre-graze mowing or topping.
- Harvesting more silage than required due to too high N applications in the previous six weeks.
Nitrogen use, pasture harvested and profit
Lower N fertiliser use is likely to reduce pasture growth, however pasture management and utilisation can minimise the impact on pasture harvested, milk production and profit. For the same amount of N fertiliser used there are several factors that will influence how much pasture is grown and harvested. Understanding these principles is key to making changes to your farm system that maintain or improve profit. For details on factors affecting N use efficiency, click here.
Dairybase data suggest a poor correlation between N fertiliser applied and profit, with some farmers making higher profits at low N use than others using higher amounts of N (see graph below). This highlights the potential opportunity to farm with less N fertiliser and maintain/increase profit.
2018-19 N applied and Operating Profit for Canterbury Owner Operators (DairyBase)


Lower N fertiliser use is likely to reduce pasture growth, however how pasture is managed and utilised can minimise the impact on milk production and profit.
N fertiliser use and profit


For the same amount of N fertiliser used there are several factors that will influence how much pasture is grown and harvested. Further details on these factors are available here.
Similarly, how pasture harvested will translate into profit will depend on several factors including:
- How efficient pasture and supplement used are converted to milk production.
- Proportion of feed going into maintenance and milk production
- Cost of nitrogen, feed and overall operating expenses
- Milk price