Traditional fertiliser programmes no longer cut it

A combination of maintaining and increasing grass/crop yields, environment challenges pertaining to reducing emissions and losses to water, along with targeting improvements in soil fertility, has brought about a change in the fertiliser programmes required on farms.

This was a key message from Pat Murphy, Teagasc Head of Environment Knowledge Transfer, who spoke as part of the recent Teagasc Virtual Soil Fertility Conference, where he explained that nitrogen, phosphorous and potassium fertiliser usage declined significantly last year.

This reduction in fertiliser usage was set against the backdrop of soil fertility levels nationally, to which 49.6% of soils were index 1 or 2 for phosphorous (P) and 44.6% of soils were index 1 or 2 for potassium (K) in 2023.

Although soil P and K indexes have improved since 2017 through to 2023, Pat noted that a lag time exists and the reduced applications of these fertilisers over 2023 means “it is pretty likely that we are going to see reductions in soil fertility as we move forward unless we change substantially the narrative around the use of P and K”.

This poses challenges for farmers, as the reduction in N fertilisers witnessed in 2023 needs to be maintained, but increases and more targeted usage of P and K compounds are required to improve soil fertility – a key component in maximising nitrogen use efficiency. At the same time, an increase in the use of protected urea – to replace both straight urea and CAN products – is required.

“To do that, we need to decouple [nitrogen from phosphorous and potassium] to increase the amount of P and K back up to what we would consider to be sustainable levels without a corresponding increase in nitrogen,” he said.

“If we are to achieve what we need to achieve over the next couple of years, the product mix that is used on most farms needs to change substantially.

“In relation to protected urea, if we don’t see substantial increases in the near future – we’ve seen relatively small incremental increases - I think regulation is likely to step into that space and I think we would be better to try and get that to happen in a voluntary way rather than letting regulation handle it,” Pat contested.

On the changes necessary at farm level, a reduction in straight CAN and low P and K CAN-based compounds are required, with more protected urea and high P and K compounds, such as 18-6-12 or 10-10-20, being included in the mix.

“If we do this and do this effectively, we can achieve the various objectives that are there in terms of soil fertility, production, environmental outcome and, if we move in this direction, it will give financial benefits because it is a lower cost fertiliser mix for the farmer,” Pat said.

To access Pat’s presentation from the Virtual Soil Fertility Conference, click here.

Also read: Irish farmers achieve key 2030 nitrogen fertiliser reduction target