Reduce N Fert Use
10 min read
Using less nitrogen (N) fertiliser on your dairy farm can improve water quality and reduce greenhouse gas emissions. The page provides guidance on how to comply with the Government's 190kg N/ha/year cap on synthetic nitrogen fertiliser, set from 1 July 2021, and what records and reports you'll need to maintain. You'll also find practical tips and strategies from experienced farmers to reduce N fertiliser use successfully without compromising pasture harvested or profit. Reviewing your N use strategy for compliance and efficiency can have positive environmental impacts and ensure you meet legal obligations. Make sure to consult regional councils or trusted advisors as needed.
Using less N fertiliser can contribute to better water quality and a reduction in greenhouse gas emissions. If reviewing your use of N fertiliser, the tips below can help you form a plan.
Looking for some fresh ideas to reduce your nitrogen fertiliser use? On this episode, we chat with Waikato sharemilker Chris Numan, who with wife Rachel has made a bunch of changes to reduce both their N fertiliser use and N losses. Find out what motivated them (not regulations), what strategies they’re using, and the results they’re seeing. Plus, on an interesting tangent, we hear about Rachel's new-found fame as a published author.
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.
The amount of synthetic nitrogen fertiliser applied to land in pastoral land use is capped at 190kgN/ha/year from 1 July 2021.
Pastoral land use means the use of land for the grazing of livestock. It doesn't include the grazing on the stubble of a crop that has been harvested after arable land use.
The nitrogen cap applies to a 'contiguous land holding’. This is ‘one or more parcels of land within a farm’. So, if there is a support block contiguous (joined) with the milking platform, it is all subject to the same N-cap. If the support block is separate, both blocks must independently meet the N-cap.
All dairy farmers will need to record the tonnages of all synthetic nitrogen fertiliser applied on-farm and the area it was applied to. Dairy farmers will then have to report to their regional council on the amount used each year on the dairy platform. The first report is due to your regional council on 31 July 2022, covering the period from 1 July 2021 to 30 June 2022. More detail on what and how farmers must report this information will become available from regional councils.
Farmers that exceed the N cap will need to apply for a resource consent. Please get in touch with your regional council if you think you will need a consent.
For more detailed information on the N-cap, see the Nitrogen cap rules page.
We have put together some common questions and answers to help you understand the requirements.
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.
Successful transition requires planning and time. It is best to do it gradually, rather than in one big step (especially if the reduction is bigger than 50-60 kg N/ha/yr). Several farmers have reduced N fertiliser successfully from +300 kg N/ha/yr to 200 -230 kg N/ha/yr but over a 3-year period. It is important that clover has time to re-establish and the additional N fixed (from increased clover growth) is available to the grass, to compensate for the lower N from fertiliser. Time is also required to ensure management systems are in place to accommodate the changes. If you are using more than 190 kg N/ha/yr you need to act now to minimise any impacts on your system, while complying with regulation.
Moving to lower application rates of no more than 40 kg N/ha in early spring and then to 0.8 kg N/ha per day of round length. N applications of 40kg N/ha are most beneficial when filling a genuine feed deficit (e.g. early spring). Mixing with other nutrients can reduce the N rate applied if other nutrients are needed. e.g. mix with Potash, DAP, Sulphate of Ammonia. Costs do increase, however there are advantages to applying nutrients like potassium and sulphate Sulphur in small amounts where there is a risk of these nutrients being lost from the root zone from rain causing drainage.
Increasing the round length to ensure grazing at 2½ to 3 leaf stage to grow more grass compared to grazing at 2 leaf or shorter where yield is significantly compromised. In Canterbury this is between 22- 24 days during the spring/summer period (generally from October-February). Where the farm traditionally has been following the cows with N, increasing round length will reduce the total number of grazings per year and ‘automatically’ will reduce the number of N applications. A longer round length will also reduce the N content in pasture and therefore reduce urinary N excretion.
Not applying N in January/February when soil mineralisation rates are high, and clover is fixing N. Mineral N is available and N is not likely to be the limiting factor for growth. To gain confidence and to check what is limiting pasture growth take herbage samples. One farmer reports pastures looking N deficient, however herbage analysis showed K was deficient, not N.
Graph 1: (Pastoral21 Lincoln Farmlet trial N Use)
Red bars: monthly application rates low N system (156 kg N/ha/yr)
Green bars: monthly application rates high N system (304 kg N/ha/yr)
Dotted line: apparent N response (extra kg N applied/extra kg DM grown)
More detailed advice on reducing N applications over summer is available which draws on Canterbury research.
Optimising conditions for clover growth, ensuring good soil fertility (pH, P, K and Mo) and grazing management to avoid continuous shading of clover. Plan also for good clover establishment when renewing pastures. Clover will fix N and compensate to some extent the lower N from fertiliser. See Alternative pasture species.
Skipping a few paddocks from routine applications when pasture growth rates are high and silage making is not wanted/needed. A weekly farm walk and constructing a feed wedge will help with these decisions.
Farmers have reported being surprised at the amount of N used at year end where they have not planned and monitored. Some ways some of the farmers are managing N to a set budget are:
For considerations on the impact on N use efficiency of the timing of application within the grazing cycle click here.
Applying less N fertiliser on effluent areas, targeting times when effluent N is sufficient. If effluent areas are consistently getting effluent, they may only need N fertiliser in early spring and possibly autumn. The N content of effluent can be variable, therefore testing may be required. Applying different amounts of N fertiliser on the effluent area may not be practical where only parts of the paddock get effluent or effluent is not spread on the paddock often. See Mick and Kirsten O’Connor’s N fertiliser plan.
Avoiding areas of higher fertility within paddocks (e.g. first 20-30 meters into a paddock, area around the trough, stock camps) and areas of the farm likely to have low response to N, e.g. dry areas, poorer species. Identify “no go areas” on the spreading map.
Addressing other factors that may be limiting pasture growth such as, soil fertility, pH, weeds, irrigation, pasture species, drainage etc. Paddock scale soil tests (P, K, S and pH) have been successfully used by several farmers for a more targeted approach to soil nutrients and requirements.
Pasture walks and "feeding the wedge" i.e. only applying N if a genuine feed deficit is forecasted. Especially hold back in late autumn when pasture response can be slow and N loss risk is high due to drainage from autumn/winter rain. Any application of N needs to ensure that the extra pasture grown is not lost through increasing residuals or topping i.e. either the cows need to harvest the pasture, or it is made into silage. See Feed wedges and rotation planners.
Coated urea (N-Protect, SustaiN) reduces volatilisation (the conversion of N in urea to ammonia gas, lost to the air). When using coated urea and conditions for volatilization are present (hot, dry and windy or moist soils in cooler situations) N applied can be reduced by 10% to grow the same amount of pasture than when applying uncoated urea.
Gibberellic acid (GA) is a growth hormone found in plants that promotes stem elongation and tiller size but is not a substitute for N fertiliser. When applied with N fertiliser good responses can be expected in early spring and autumn. Many farmers are using GA with N fertiliser specially in the autumn as a way of achieving a higher response to the N fertiliser applied. See Gibberellic Acid.
Fertigation (injection of fertiliser into an irrigation system) and urea applied as a liquid can be used to reduce rates and get even distribution of the N. Fertigation trials have not shown a higher response rate to applying N in a liquid form compared to N in a solid form (i.e. the form of N does not affect the pasture response). However, if it allows lower application rates and more precise management at an acceptable return on capital, it is a tool that can be used well on farms that are suited to the set up.
Using weather forecasting well to avoid applying N fertiliser before a significant rain/drainage event to avoid any direct losses of N fertiliser.
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.
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.
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: