Sustainability is the ‘buzz’ word for agriculture in Ireland at present, and becoming more sustainable and increasing efficiency – particularly where nitrogen (N) is concerned – is consistently topical.
Irish agriculture is already quite sustainable, with grass being a basic within our production systems, whether that is dairy, beef or sheep. However, one of the areas that we can improve upon is N use efficiency.
Speaking at a recent Department of Agriculture, Food and the Marine (DAFM) webinar discussing the draft proposal for the Nitrates Action Plan (NAP), Laurence Shalloo, a researcher with Teagasc, outlined research looking into the impact of nitrogen management strategies on the sustainability of grass-based dairy systems.
The research looked at changing the time that fertiliser was applied, along with looking at the level of fertiliser applied.
Non-compliant slurry spreading during the closed period, was also looked at during the research.
Nitrogen leaching
The research determined that the factor that had the biggest impact on nitrate leaching/ha, at a level of 1m, was the weather.
Shalloo noted: “With management practices being the exact same, there was a large variation in nitrates lost – from 39kg to 88kg N/ha from year to year.
“2018 saw a large amount of N leaching due to the weather conditions, when compared to 2010.”
Chemical N
The biggest impact on chemical N loss was also the weather, with 2018 seeing a large amount of leaching compared to 2010 and 2011.
The research also determined that reducing N spread from 250kg/N down to 225kg/N, reduced leaching by 1.4kg/ha or 2.3%.
So, reducing the amount of chemical N spread is reducing loss, but the reduction is less than what was expected.
Increasing the amount of chemical N spread does also increase the amount of leaching that occurs.
Increasing the amount of chemical N spread from 250kg/ha to 300kg/ha increased N leaching by 2.9kg/ha or 4.7%.
Slurry spreading
The research also determined that the spreading of slurry during the closed period also contributed to N leaching.
On a farm where 12% of the slurry was spread during December, N leaching increased from 61.9kg/ha to 65.1kg/ha – or 5.2%.
Shalloo highlighted that, again, there was a significant year to year variation, depending on the weather.
Precision management
Shalloo stated: “This highlighted the need for precision management on farms.
“We can reduce N loss through leaching by reducing chemical N usage during adverse weather conditions, and avoiding the spreading of slurry during the closed period.”