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The answer to high fertiliser prices is under our feet

September 16th, 2023 10:00 PM

By Southern Star Team

The answer to high fertiliser prices is under our feet Image

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SOIL health is drawn into focus as the challenges around fertiliser price and fertiliser limits continue.

Irish soils are amongst the most productive and healthiest soils in the world, however we can do more to tackle the short, medium and long term challenges of Irish agriculture.

The soil contains a large pool of labile nitrogen (N). The labile N can be converted from an organic form to a plant available form of N through the process of mineralisation.

Mineralisation is driven by soil biological activity. Studies carried out by Grassland Agro have found that grassland soils across the island of Ireland have on average a store of 350 kg/N/Ha of labile N which could potentially be made available throughout the year.


The key to unlocking the soils labile N is through optimising the three pillars of soil health: Soil chemical, physical and biological properties. Soil chemistry is the representation of a soils fertility using soil pH and Morgan’s soil test.

It is important that soil pH is maintained as is the single major factor dictating overall soil health. Soil biology can now be tested by using the Bioscan Solvita test. Soil structure can be assessed using the Grass VESS method.

Grassland Agro have over 40 agronomists across the country working with farmers to optimise soil health and perform sampling. In the same study performed in 2021, it was found that soil structure poses a major threat to overall soil health and soil mineralisation potential on grassland soils.


It’s our soil biology that turns organic N (plant unavailable) into plant available N through a process called mineralisation. Mineralisation is a simple process where the organic nitrogen is broken down by fungi, bacteria and earthworms and turned into plant available forms.

It is paramount that soil pH is optimised (6.3-6.5) to ensure a habitat for soil biology to live and work effectively. Increasing the bacteria and fungi in the soil will release more N.

Mineralisation will also increase phosphorus (P) and Sulphur (S) availability from soil reserves. The soil supply of N from mineralisation will become available throughout the year from the soil reserves.

Subsequently by increasing this baseline of N from the soil reserves, application rates of chemical N can be reduced.


Soil structure is very important to provide the best living conditions for soil fungi, bacteria and earthworms.

Soil pH has a very important role in soil structure as it can help create structure in the soil and also increase biological activity and root development.

Structure is also very important in determining nutrient availability; the impact of poor soil structure can be seen during the summer as P becomes less available to the plant and as a result, animals can be seen licking or chewing on stones. This is sometimes witnessed on soil P index 4 soils but the nutrients cannot be taken up by the plant because of poor soil structure.

Soil structure also results in poor or shallow rooting. Roots are very important as they are responsible for the uptake of nutrients. Optimal soil structure creates better drainage, warmer soils, early grass growth and causes better nutrient filtration and storage to improve water quality.


Through priming and kick starting soil biology and improving soil structure through the application of a soil conditioner like Physiolith, more N can be unlocked from the soil reserves. On farm trials have shown an additional release of 60 kg N/ha from the soil in a single season. These soil conditioners will increase the efficiency of the chemical and organic fertiliser applied throughout the year, reducing the requirement for chemical N.

Physiolith is an ideal partner for organic manures such as slurry and will fast track the release of the organic fraction of slurry N which can be used to offset chemical nitrogen.

Maximising the soil supply of N through mineralisation due to increased biological activity will offset chemical N and maintain growth as legislation and fertiliser reductions loom.

These soil properties are fundamental to tackling the environmental, economic and social sustainability issues facing all Irish agriculture.

If you would like to find out more about Grassland Agro and what services we provide, you can do so by contacting your local Grassland Agro representative

Aisling Sheehan: 0871957867 – [email protected] – covering areas of Lisavaird, Barryroe, Ballinhassig and Carrigaline.

Thomas O’Sullivan: 0879903775 – [email protected] – covering areas of Drinagh, Bandon, Tarelton and Killumney.

Visit our webpage and following us on our social media channels.

You can also tune in to our podcast The Sod Pod streaming fortnightly.

Finally, due to on going continued expansion we are recruiting more Technical advisors in this region. If you think you are suited to our organisation feel free to e-mail a cover letter and your CV to: [email protected]

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