Dr Debbie McConnell, an AFBI researcher, highlighted the value of grass as a feed with higher fertiliser prices at a recent joint webinar from AFBI, Agrisearch and CAFRE.
The webinar focused on using fertilisers effectively in the light of recent price increases.
Dr McConnell indicated that CAN prices rising from £300 to £600 per tonne has increased the cost of producing 1kg of grass by £11 to £22.
Higher fertiliser prices
She explained that across a typical 40ha grazing platform, that equates to an additional cost of £8,940/year.
In turn, this is 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 farmers.
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 five times greater than the cost of the fertiliser.
According to Dr McConnell, 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 fertiliser cost.
However, it still remains “significantly greater” than the cost of the fertiliser.
Furthermore, with the significant increase in fertiliser price, she explained that it is essential to maximise grass response from any fertiliser a farmer applies through good management practices.
Soil fertility and health
Aveen McMullan, Senior Agricultural Technologist, CAFRE, went on to echoed her views by highlighting the importance of soil fertility and soil health.
She encouraged all farmers to carry out soil analysis to determine pH and identify low phosphorus (P) and potash (K) index soils.
She 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.
To maximise growth this season, Aveen urged farmers to carry out soil structure and sward assessments to identify issues that could impede growth and reduce production from grass swards, such as compaction, poor drainage and weed populations and take appropriate action.
Slurry’s value
She advised that farmers should view organic manures such as slurry and farmyard manure as a valuable source of nutrients.
According to McMullan, 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).
Furthermore, she stressed the importance of targeting organic manures at low index soils to maximise slurry utilisation and grass production where possible.
Slurry spreading equipment
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 (LESS), such as a dribble bar or trailing shoe, to maximise efficiency.
She stressed that regular maintenance and calibration of slurry and fertiliser spreading equipment are “essential” to ensure correct application.
She advised that farmers can “greatly improve” the accuracy of applications by utilising technology such as GPS guidance and variable rate application where available.
Nutrients Action Programme
She also provided a summary of the relevant Nutrients Action Programme Regulations.
She provided details of buffer zone or no spread areas along waterways required when applying fertilisers.
Furthermore, she reminded farmers spreading slurry that during February, buffer zones increase from 10 to 15m (from 3m to 5m if using LESSE). Maximum application rates reduce to 30m3/ha or 2700 gallons/acre.
