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News > Fertiliser challenges this year – what can farmers do?


Fertiliser challenges this year – what can farmers do?

February 10, 2022

Using fertilisers effectively in the light of recent increases in the cost of fertiliser was the topic of a recent joint webinar from AFBI, Agrisearch and CAFRE. A number of speakers addressed issues affecting the cost effective use of fertilisers and the following is a summary of the event.

Value of grass as a feed with higher fertiliser prices

Dr Debbie McConnell, AFBI researcher, indicated that CAN prices rising from £300 to £600 per tonne has increased the cost of producing 1kg of grass by £11 to £22. Across a typical 40ha grazing platform that equates to an additional cost of £8,940 per year and a £5,161 and £7,868 increase per year for 2-cut and 3-cut silage regimes, respectively.

Despite this, given the high cost of alternative feeds, good quality grass remains the cheapest feedstuff available to N.I. farmers and the ratio of grass feed value to fertiliser costs is still positive in many cases.

Work recently collated with the support of Agrisearch indicates that the feed value of the grass grown over a season from an application rate of 200kg nitrogen(N)/ha, with CAN costed at £300/t, is 5 times greater than the cost of the fertiliser. When CAN price rises to £600/t, the grass feed value over the season from the same fertiliser application rate is reduced to 2.5 times the cost of the fertiliser, but still remains significantly greater than the cost of the fertiliser (Figure 1).

Figure 1: Impact of CAN fertiliser cost on grass value-fertiliser cost ratio at an application rate of 200kg N/ha

However, with the significant increase in fertiliser price it is essential to maximise grass response from any fertiliser applied through good management practices.

Importance of soil fertility and soil health

Aveen McMullan, Senior Agricultural Technologist, CAFRE, went on to highlight the importance of soil fertility and soil health.  Aveen encouraged all farmers to carry out soil analysis, to determine pH and identify low phosphorus (P) and potash (K) index soils. 

Aveen showed the effect of low pH on fertiliser efficiency, explaining that as pH increases from 5 to 6-6.5 a greater percentage of the N, P and K applied will be utilised by the plant and less fertiliser will be wasted as illustrated in Figure 2.

Figure 2: Potential nutrient and financial loss due to low soil pH.
Source: Teagasc/DAERA 2017, based on applying 150kgN/ha of 27.4.4.

To maximise growth this season, Aveen urged farmers to carry out soil structure and sward assessments to identify issues which could impede growth and reduce production from grass swards, such as compaction, poor drainage and weed populations and take appropriate action.

Organic manures such as slurry and farmyard manure should be viewed as a valuable source of nutrients available on farm.  Using standard figures, every cubic metre of a typical 6%DM slurry will supply 1kg N, 1.2kg P and 2.3kg of K (9 units N, 11 units P and 20 units K per 1000gal).  Aveen stressed the importance of targeting organic manures at low index soils, to maximise slurry utilisation and grass production where possible.

The CAFRE online Crop Nutrient Calculator available at DAERA online services, provides a simple and easy to use fertilisation planning tool.  Aveen demonstrated how the calculator can be used to plan and budget fertiliser purchases this season, as well as satisfying the requirements to produce a fertilisation plan.

A soil sampling service is available through your local DAERA Direct office, simply phone or email to order a sampling kit. 

To optimise the potential of manures and achieve maximum effect, Aveen recommended applying nutrients when soil temperatures are suitable for grass growth and using Low Emission Slurry Spreading Equipment (LESSE), such as a dribble bar or trailing shoe, to maximise efficiency. 

Regular maintenance and calibration of slurry and fertiliser spreading equipment is essential to ensure correct application and accuracy of application can also be greatly improved by using technology such as GPS guidance and variable rate application where available.

Aveen also provided a summary of the relevant Nutrients Action Programme Regulations, outlining the buffer zone or no spread areas along waterways required when applying fertilisers and reminding farmers spreading slurry that during the month of February that buffer zones increase from 10 to 15m (from 3m to 5m if using LESSE) and maximum application rates are reduced to 30m3/ha or 2700 gallons/acre.

Managing fertiliser applications on dairy farms

Robert Patterson, CAFRE Dairying Technologist, presented nutrient management plans for dairy farmers planning to produce grass for turnout and first cut silage. The scenarios were generated using the DAERA online Crop Nutrient Calculator and assumed adequate levels of soil fertility with a pH of 6.2 and P index and K index of 2+.

Robert highlighted the valuable contribution that slurry can make to meeting crop needs.  For example, applying 28 m3/ ha (2,500 gallons/acre) slurry using LESSE technologies came close to meeting the P and K requirements of a first cut silage grass crop.  As a result only an additional 330 kg/ha (2.7 bags/ acre) of CAN needed to be applied to meet all the nitrogen needs of the crop. 

Two grazing scenarios were presented based on an early March and mid April turnout. In both the importance of getting out and walking the fields early was emphasized, to measure grass covers and assess soil traficability. Robert talked through situations where applying lower rates of slurry (22 m3/ ha or 2,000 gallons/acre) to the grazing platform would be an appropriate way to reduce the requirement for early spring nitrogen (23 kg N/ ha and 19 units/ acre).  Applying early nitrogen fertiliser from late February onwards can only be profitable if conditions are optimum and the grass grown can be utilised.

Robert highlighted the need to focus on controlling the factors within the farm gate to increase the efficiency of nitrogen applied. These included assessing conditions at sowing, little and often applications, measuring grass utilisation and applying sulphur.

Managing fertiliser applications on beef & sheep farms

Rachel Megarrell, CAFRE Beef and Sheep Adviser, stated that for beef and sheep farmers it will be a balancing act between purchasing and sowing the correct amount of chemical fertiliser to achieve the growth required to graze livestock and to also produce the silage that is required to feed them over the winter months.  Rachel highlighted that target yields will vary for individual farms depending on grass type, age of sward and livestock requirements and therefore nitrogen application rate should be correlated to the tonnage of grass required.

Having a clear plan in place that relates to your winter feeding strategy this year is critical and the key here will be to estimate the amount of silage required to meet animal requirements efficiently and effectively for the number of stock to be held on farm.  Rachel went on to present a practical scenario based on a beef and sheep example stepping through the completion of a fodder budget and from that determining the yield that your land is capable of producing to setting the target area to be closed off for harvest, providing slurry and fertiliser recommendations for 1st and 2nd cut silage and finally establishing the cost associated with growing that crop based on current fertiliser prices.

Using a current soil analysis report, target slurry supplies to land that requires P and K and give priority to land that will be cut for silage.  Slurry is a valuable resource and must be applied at the right time, at the right rate using the right equipment.  Chemical fertiliser can then be used to top up to meet crop requirements.

Farmers should look critically at the grazing systems that they currently have in operation on farm and revise these with the aim to maximise grass utilisation in order to get the best return from the chemical fertiliser that has been applied.  Consider a move away from a set stocked grazing system to a rotational or paddock system which aims to graze the grass plant at the correct stage and then allow a period of recovery to take place.  Longer term continue with soil sampling and apply lime per analysis to ensure chemical inputs are maximised.

Rachel concluded with the message that expenditure on fertiliser must be clearly thought out this year.

Reducing reliance on fertiliser N

The webinars concluded with Dr David Patterson, AFBI researcher, outlining how grassland farmers could reduce their reliance on fertiliser N in the future. He indicated that increasing species diversity with legumes can improve grassland sustainability, reduce fertiliser N inputs and still achieve comparable levels of sward productivity and animal output.

Legumes such as red and white clover are best suited to cutting and grazing swards respectively. Clover rich swards can fix biological N from the atmosphere which can sustain similar levels of sward productivity to grass-only swards reliant on fertiliser N. A healthy grass/white clover sward with 20-30% clover content can fix 150 kgN/ha which represents both a potential financial and environmental saving. White clover’s growth habit is very compatible with the more upright grasses in a mixed sward, has higher digestibility value, and results in higher levels of animal intake. Research shows that higher stocking rate dairy farms could reduce fertiliser N from 250 to 150 kgN/ha, make full use of biologically fixed N, and produce similar yields of herbage. Beef cattle farms could reduce fertiliser N use down to 50 kgN/ha and still achieve 90% of the livestock performance, compared with grass-only plus 220kgN/ha. From an environmental perspective, in a healthy grass/clover-based system the biologically fixed N is carbon and energy neutral, the nitrous oxide emissions are much lower and there is a lower overall carbon footprint.

However a different grassland management approach is required to achieve these advantages, for establishment, weed control and persistence of clover in the sward over the longer term.

If you missed these webinars, you can catch up by visiting here: