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Why would You Apply Lime?

19 July 2018
Type Media Article

By Shane Devaney, Beef & Sheep Adviser, Longford Town

This very dry spell of weather has made it an ideal opportunity to apply lime. The optimum pH (a measure of acidity) for grassland is between pH 6.0 to 6.3 and we can find this out from a soil sample. We are in a very lucky position at the moment as there are a large number of farmers participating in GLAS who have a full set of soil samples for their farms so it is very easy to help them identify fields that will benefit from lime.

Lime helps the soil make better use of slurry, farmyard manure and chemical fertiliser. At the correct pH the availability of nitrogen (N), phosphorus (P), potassium (K), sulphur (S) and calcium (Ca) increases. Studies show that where lime is deficient, up to 80% + of nutrients applied may get locked up in the soil and will not be fully available to grow grass. This means the grass may only receive the nutrients from two bags of fertiliser in every 10 bags applied. This is like selling 10 cattle in the mart and only getting paid for two. Lime also promotes better drainage and aeration of the soil due to increased worm and other micro-organism activity. On heavier type soils “a little and often approach” is recommended i.e. approximately 1 tonne of lime per acre. On drier soils it is safer to go with 2 tonnes per acre where needed.

It is important to say that for silage it is better to lime after cutting, as high uptake of lime can increase the pH in the silage which affects silage preservation. Another point to note is that if slurry is first applied leave a week before spreading lime.  If lime has been applied avoid slurry application for 3 months. Lime costs in the region of €20/tonne spread and studies have shown lime applications can give a 7:1 return on investment. We are encouraging you to think about lime to improve grass growth and make more efficient use of chemical and organic fertilisers.”