A leading Teagasc climate advisor has welcomed the significant upturn in agricultural lime usage recorded throughout Ireland over recent years.
Dr. Seamus Kearney is based in Dungarvan, Co Waterford. He spoke at a recent soil health webinar, hosted by Teagasc.
Kearney confirmed the significant drop in Irish nitrogen (N) fertiliser usage levels recorded since 2018; falling from a figure of 400,00t in 2018 down to almost 300,000t in 2023.
This reduction is meeting Ireland’s climate change target heading towards 2030.
Assessing soil conditions
According to Kearney, farmers should assess the fertility of their farm on a field to field basis.
“Red and green bottle tops can be nailed to posts at the entrance of each field or paddock as a phosphate (P) and potash (K) designation code,” he explained.
“Farmers should be targeting Index 3 values, where both these key plant nutrients are concerned.”
The Teagasc representative stressed the role of soil pH values in determining P and K index values.
Adding 5t of lime/ha to acidic soils can lift P and K Indices from a value of one up to three.
Where the addition of nitrogen fertiliser is concerned, Kearney highlighted the benefits of applying compounds, such as 18:6:12 and 10:10:20.
“Building up soil P and K reserves will improve nitrogen use efficiency. Straight N should be applied to grassland in the form of NBPT urea,” he said.
Slurry and lime spreading
When it comes to making best use of animal slurries, Kearney confirmed the use of low emission slurry spreading (LESS) systems.
“Trials have confirmed that putting slurry out in the early spring with LESS, triples nitrogen utilisation rates relative to slurry spread with a splash plate in the middle of summer,” he said.
“Approximately 60% of the slurry put on to fields is now applied using low emission spreading systems.”
Kearney pointed out that lime and potash can be spread on land without any restrictions being imposed.
“Clover has the capacity to fix up to 120kg of N/ha from the atmosphere on an annual basis,” he commented.
“But clover requires a soil pH range of 6.2 to 6.5 to maintain optimal levels of viability. This is why the issue of soil fertility boils down to three key criteria pH, P and K status.
“Getting these values correct will allow Irish farmers to reduce chemical N application rates while still achieving the crop output levels they want to obtain.”