Nitrogen fertiliser cap
Are you wondering how your N fertiliser use is stacking up against the new freshwater regulations? In this blog post, Charlotte doesn’t just explain the new rules but also offers great insight into how to adapt your farm management practices to comply with them.
We have covered already several aspects of the new Essential Freshwater regulations which came into law in September this year: agricultural intensification, stock exclusion and winter grazing management.
Today on the blog, we are wrapping up this mini-series with a summary of the synthetic nitrogen (N) fertiliser cap. We go into details about the specific rules and data on N fertiliser use in Canterbury, outline pathways to transition to lower N use, and highlight the stories of other farmers who have experience in reducing N fertiliser use.
New rules on n fertiliser use
What are the rules on synthetic nitrogen fertiliser use?
To be a permitted activity, i.e. no resource consent required, the amount of synthetic nitrogen fertiliser applied to land in pastoral land use will be capped at 190kgN/ha/year from 1 July 2021.
The N cap applies to the average N applied across the farm and to every hectare of pasture (area not used to grow annual forage crop).
Cannot be offset against non-grazed / ineffective land.
You can put more than 190kgN/ha/year on forage crops only if offset by applying lower amounts on pasture.
Pastoral land use means the use of land for the grazing of livestock but does not include the grazing on the stubble of a crop that has been harvested after arable land use. The cap does not apply to arable or horticulture crops.
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 run-off is separate, both blocks must separately meet the N-cap.
Synthetic nitrogen fertiliser is defined as being >5% N v weight and does not include alternative sources of N like compost.
Recording and reporting
All dairy farmers will need to record and report to their regional council from 1 July 2021:
Areas of land in pasture, annual forage crop, and other land use;
Receipts for purchase of all synthetic N fertiliser, showing fertiliser type and % N; and
Date and rate of application to each land area.
If the N cap cannot be met by the 2021-22 season, farmers can apply for a resource consent.
Two options are available:
Consent for a non-complying activity requiring a synthetic N reduction plan that demonstrates how the farm will reduce their use of synthetic N by 1 July 2023
Consent for a non-complying activity requiring the farm to ensure that the rate at which N may enter water because of the application of synthetic N fertiliser does not exceed the rate that would enter water if 190kg N/ha/year was applied. This will be granted for a maximum term of 5 years.
Important to note:
Both options will require input from a qualified and experienced consultant.
Non-complying activities are the most stringent – you will have to show the adverse effects are minor, and the consent application comes under more scrutiny ($$).
Regional councils are still working on the details on how this will be implemented at a local level
Detail of recording required?
How is this going to be monitored?
Non-complying consenting options
(These rules were interpreted on the 1 December 2020, and the details are subject to change.)
Central Government will review the N cap in 2023, and the requirements may change. In the long-term, it will probably be replaced by regional limits set by each regional council to reflect the different geography of a place.
Nitrogen 101
Why is nitrogen applied to pasture?
N is an essential element for plant growth and biological function.
New Zealand grass/clover pastures are inherently N deficient and will respond to N fertiliser when growth conditions are right.
When N fertiliser is applied during good pasture growth conditions and additional pasture is utilised to produce milk, N fertiliser use is nearly always economical.
It can be easier to manage N-fertilised pasture than clover-based pasture because of greater predictability of pasture production and less year-to-year variation.
Nitrogen application has increased more than six-fold in New Zealand since 1990 due to intensification of farm systems. Many farmers have moved from a tactical use of N fertiliser to fill feed deficits, to production systems that rely on N fertiliser all year round.
When plants don't take up the nitrogen, it enters waterways and leads to nutrient pollution in rivers and groundwater.
Current Nitrogen Use in Canterbury
How many farms will be affected?
Compared to other regions, irrigated farms in Canterbury have a relatively high use of N fertiliser. Canterbury farms have a high N use as they can expect higher response rates to fertiliser (10-15 kg DM/kgN applied) making N-boosted grass a very price competitive feed.
The higher N fertiliser use in Canterbury demonstrated in recent Ravensdown data that the average nitrogen use for dairy farms was 234 kgN/ha/yr in Canterbury, 171 kgN/ha/yr in Southland and 128 kgN/ha/yr in Waikato/Bay of Plenty.
The average N use in the 2018/19 season on Canterbury dairy farms from different sources is presented in Figure 1. It shows that the average dairy farm in Canterbury will have to decrease their nitrogen fertiliser use by about 40 – 50 kgN/ha/yr or 20%. Of course, these figures only show the average. Some farms will be required to reduce by more.
Figure 1: The average N use in the 2018/19 season on Canterbury dairy farms from different sources.
A large irrigation scheme in Canterbury has found that 70% of their dairy farmer shareholders exceed 190 kgN/ha/yr. That is not to say that the dairy sector will be the only one impacted. Data from another large Canterbury irrigation scheme shows that while the average irrigated sheep and beef fertiliser use is about 150 kgN/ha/yr, the farms of the top 25% percentile for N fertiliser use were applying 220 – 290 kgN/ha/yr.
Strategies to reduce nitrogen use
Transitioning to lower N use – how easy is it?
From 1 January 2021, there will be only six months to make the change to a biological system! Clover needs time to re-establish and be actively fixing N.
Some dairy farmers are using 300 kgN/ha/yr.
Reducing to 230 kgN/ha for most is relatively easy over 2-3 years
However, significant reductions (+ 60 kg N/ha) will require time to adapt to the new system to minimise the impact on pasture production.
It is important to reduce any other factors that might limit pasture growth, like poor soil fertility, weeds, irrigation etc.
A successful transition requires time and is better to be made in stages rather than in one blow. Start making a plan, following it and monitoring progress now! This will include a solid review of all farm inputs/costs – our consultants are happy to assist you with this.
Farmers experiences
Charlotte has been attending workshops held by DairyNZ for the Hinds / Selwyn ‘Meeting a Sustainable Future’ project. The following strategies were reported by DairyNZ in the handout from the workshops, and are based on experiences from farmers who have successfully reduced their N fertiliser rate without compromising pasture harvested or profit. Many of them are supported by science.
1. Application rates
Use applications of maximum 25 to 40kg N/ha.
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) and pasture growth conditions are optimal. High pre-grazing covers and residuals from higher N rates should be avoided.
Mixing with other nutrients can reduce the N rate applied if additional 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.
2. Timing of applications
Do not apply fertiliser at low soil temperatures (<6°C), as pasture growth is limited, and a response will not occur until soil temperatures rise again.
Reduce or do not apply N fertiliser in late autumn, when the average cover is sufficient. The pasture response then is low, and the risk of drainage increases.
Do not apply fertiliser at high soil temperatures (>16°C) which inhibit grass growth and limit response to N fertiliser. For example, the Pastoral 21 trial shows the apparent N response rate to N applied is relatively low over the January/February period, at less than 5 kgDM/ha vs over 15 kgN/ha in November.
Skip or reduce N applications on paddocks in summer when clover content and soil mineral N is high. N is not likely to be the limiting factor for growth. This has been a popular strategy with mixed results, e.g. ending with feed deficit in March. To gain confidence and to check what is limiting pasture growth, take herbage samples. One farmer reports pasture looking N deficient; however, herbage analysis showed K was low, not N.
Any application of N needs to ensure that the extra pasture grown is not lost through increasing residuals or topping.
3. N fertiliser and pasture management
The pasture height needs to be above 3.5cm (~1500kg DM/ha) to respond to N fertiliser.
Increase the round length to ensure grazing at 2½ to 3 leaf stage to ensure pasture quality is maintained and high growth rates are utilised. 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.
Within four days after application, pasture does not respond to N fertiliser. This means it could be grazed without a response penalty in the following re-growth period.
Optimising conditions for clover growth, ensuring good soil fertility (pH, P, K and Mo) and grazing management to avoid continuous shading of clover.
Plan for good clover establishment when renewing pastures. Clover will fix N and compensate to some extent the lower N from fertiliser.
Addressing other factors that may be limiting pasture growth such as soil fertility, pH, weeds, irrigation, pasture species, drainage etc. Several farmers have successfully used paddock scale soil tests (P, K, S and pH) 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.
4. Placing of N fertiliser
Applying less N fertiliser on effluent areas, targeting times when effluent N is sufficient. If these areas are consistently getting effluent, they may only need N fertiliser in early spring and possibly autumn. The N content of effluent can vary; therefore, testing may be required.
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.
Skip 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.
5. Additional products and technology:
Coated urea (N-Protect, SustaiN) reduces volatilisation. When using coated urea and conditions for volatilisation are present (hot, dry and windy or moist soils in colder 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, especially in the autumn as a way of achieving a higher response to the N fertiliser applied.
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 setup.
An example - N Fertiliser Policy Lincoln University Dairy Farm
The Lincoln University Dairy Farm (LUDF) had a significant change in the nitrogen use strategy over the last few years.
2010-13 300 kgN/ha: The spread of the clover root weevil in Selwyn in the early 2010s decimated clover on many local farms including LUDF, prompting an increase in N fertiliser use from around 190 kg N/ha to 250 – 350 kg N/ha. Eco-N was used during this period to reduce the risk of N leaching until it was removed from the market in 2013.
From 2014/15 170 kgN/ha – The farm has focused on reducing nitrogen fertiliser by implementing a low input / high production system, using principles from the Pastoral 21 research project. Pasture growth has reduced by about 1.5 tDM/ha/yr, and clover has returned to the pastures as it was before the clover root weevil outbreak.
Figure 2: Nitrogen fertiliser (kgN/ha) applied at Lincoln University Dairy Farm and in Canterbury (average from DairyBase).
The reduction in N fertiliser was implemented using two main methods:
Changing the frequency and amount of N applied at each event – contributing to 85% of the overall reduction in N applied. No N is applied after the end of March.
Markedly reducing N fertiliser application to the effluent areas – contributing to 15% of the reduction in total N applied.
Summary of key points in the change in fertiliser management was: (LUDF data analysed by David Chapman - DairyNZ.)
2.4 fewer applications per year, and an average of 8 kg N/ha less N applied at each fertiliser spreading event.
The fewer applications per year were, in turn, facilitated by 1.7 fewer grazings per year, reflecting a mean 4-day increase in rotation length.
Longer rounds/fewer grazings resulted in higher pre-graze targets: an increase in leaf stage at grazing of ~ 0.3 leaves/grazing, which was estimated to have recouped about 1.1 t DM/ha of the expected reduction in pasture growth resulting from removing N fertiliser. Having a high percentage of tetraploids in the pastures and pre-grazing moving has helped.
This ‘buffered’ the expected sizeable negative effect on pasture production of halving N fertiliser inputs.
References
Strategies to reduce nitrogen use summarises findings from the:
DairyNZ Community of Interest Meeting Handout, Selwyn and Hinds project, November 2020
DairyNZ Community of Interest Meeting Handout, Selwyn and Hinds project, June 2020
DairyNZ meeting a Sustainable Future Meeting Notes: N Fertiliser use discussions; Virginia Serra, July 2020
Lincoln University Dairy Farm field day handout, interpreted by David Chapman and Virginia Serra
DairyNZ Technical Series article, Nitrogen fertiliser use: the right amount, in the right place, at the right time, Mark Shepherd and Diana Selbie, December 2017
DairyNZ Technical Series article, Tactical use of nitrogen fertiliser, Ina Pinxterhuis, December 2019
Code of Fertiliser Practice published by the Fertiliser Association of New Zealand.
If you have any questions about the new N cap and reduction strategies, leave a comment below or contact Charlotte.
Author: Charlotte Irving
