Reducing the application rate of nitrogen (N) fertiliser by 25kg and 50kg N/ha could reduce farm profitability by 5% and 10% respectively, based on the results released in a new Teagasc study.
A new report called ‘Review of the Influence of Nitrogen Application Rate, Soil Type and Agroclimate Location on Grass Production, Feed Budget, Nitrogen Use Efficiency and Farm Profitability’ was published by Teagasc yesterday (Tuesday, November 24).
This was released on the same day as day one of the Teagasc Virtual Dairy Conference.
The greenhouse gas marginal abatement costs are large when the reduced grass dry matter (DM) production is replaced with imported feed onto the farm, the report noted.
Meanwhile, reducing N application rate by 20% on suckler beef farms reduced gross margin per hectare by 7% and net margin by 12%.
Reducing N application rate by 22% on lowland sheep farms reduced lamb output per hectare by 15% and net margin per hectare by 16%.
However, incorporating white clover into existing pastures and use of NUE (nitrogen use efficiency) technologies has the potential to reduce these negative economic impacts, it was added.
A number of other key findings were also highlighted in the report, including environmental research and technology study.
It was noted that a review of six large-scale dairy cow grazing experiments in the Republic of Ireland predicted that the rate of N which gave the maximum percentage change in stock carrying capacity was approximately 300kg N/ha on both freely and imperfectly drained soils.
N surplus increases with increased N fertiliser application and increased stocking rate, which increases the risk of N loss.
There is a variable time lag – ranging months to decades – between N surplus losses and changes to water quality and this must always be acknowledged when considering the efficacy of programmes of measures.
On a more positive note, greater use of low emission slurry spreading technology, protected urea, increased soil fertility (including soil pH) and greater precision in grazing management have the potential to reduce N required for a given level of grass growth which would reduce N emissions.
However, the adoption of this technology at farm level has been very limited; it will require a number of years before there are sufficient uptake to replace significant levels of chemical N fertiliser. A considerable knowledge transfer and a continued research programme are required to get significant adoption.
Grass-based systems are focused on maximising grass production and utilisation and minimising the amount of feed imported onto the farm. This is both more profitable and more environmentally sustainable.
A move to lower grass production “carries the risk of greater importation of feed onto the farm which will lead to reduced profitability and a deterioration in environmental sustainability as has been demonstrated around the world”, the report said.