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Lime: The forgotten fertiliser

Posted on 16 January 2017

Lime is often considered the forgotten fertiliser. One of the reasons for this is before the advent of granulated lime, you could not effectively store lime on the farm. It was a difficult and time consuming task to apply lime, so its use has fallen off over the years and as a result, pH levels continue to drop. Granulated lime has been available for years and can be stored on farm and is easily applied.

The use of granulated lime is growing year after year, due in no small part to its ease of application. Farmers can order granulated lime in various package sizes and have it sitting in the shed ready to go when the weather turns and the fields are ready for sowing. It is loaded and spread in the same method as fertiliser with the same equipment, making it an ideal way to correct the soil pH. There is no need to co-ordinate with others and compaction risk is minimized, and because superfine lime is in granular form, the most effective and reactive part of the lime lands on the intended target instead of drifting away.

When sourcing granulated lime, the same as for AgLime, it is important to consider the Neutralising Value (NV) of the lime source and the fineness of the lime used to make the granulated lime. Always ask for this information before making your purchase decision. Granulated lime in Northern Ireland can be sourced with a NV as high as 54.3%CaO and with >99.7% passing through a .125mm sieve and >70% passing through a .063mm sieve. Do not fall prey to claims of more effective products, ask for the data to back it up.

Because granulated lime is made of superfine limestone dust, there is far more particle surface area in a granule than in the particles of AgLime, (picture in your mind, holding a handful of gravel in one hand and a large stone in the other, there is far more surface area on the gravel than the stone) and therefore granulated lime has a greater potential reaction with the acid soil solution. This means you can use less granulated lime to get the same pH correction as AgLime. Therefore, a high quality granulated lime such as the specification listed above, 150Kg is required for the same pH lift as 1 tonne of AgLime. When comparing the cost of granulated lime to AgLime, always work the price back to volume applied per acre and granulated is often more cost effective than AgLime.

When sowing lime, consider the time required to achieve the desired pH correction. Often times we sow lime when sowing a new crop. Ideally pH will be adjusted before germination to give the new crop the best possible start. Because it takes AgLime longer to react in the soil and because larger particles will not fully break down, AgLime should be applied 4-6 months prior to planting. This usually means applying to the prior crop and ploughing down the lime, this is impractical. Granulated lime solves this problem as it starts working immediately with the best granulated lime having a 97.9% reactivity and full effect within 4 – 6 weeks of application.

Granulated lime is easy to store on farm, easy for the farmer to apply, lands on target and is fast reacting. It makes sense we use more of it to raise soil pH, making the most of the soil nutrients and give establishing crops the best possible start. It is time we make better use of the forgotten fertiliser.

Now is the time to take advantage of the benefits granulated lime gives you.