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Benefit from applying lime to grassland now

By: Philip Cosgrave

It might surprise you to know that two thirds of all grassland soil samples received by the lab have a soil pH which is too low, but it's never too late to correct this with lime


Benefit from applying lime to grassland
Benefit from applying lime to grassland
Correcting soil pH should be a priority for all livestock farmers

The cost of rectifying soil pH is an investment that should deliver impressive returns. Correcting soil pH will provide the right environment for your ryegrass and clover to reach its potential as well as:

  • Increase phosphorus and potassium availability
  • Improve biological activity and in turn improve supply of nutrients from organic matter
  • Increase earthworm activity and soil structure
  • Improve the persistency and competitiveness of the productive species within the sward
  • Increases calcium and magnesium supply for grass and livestock 

Teagasc research has shown that on a low pH soil where only lime was applied an extra 1 tonne of grass dry matter was grown, it also resulted in an increase in soil available phosphorus. 

Late autumn applications of lime on grassland are not too late!

Traditionally many growers will apply lime in the spring, but is this always the right decision.

Who knows what the spring will bring weather wise! If you have soil results back early enough and lime is required, then it’s never too late to apply lime if fields are dry enough. Applying lime in late autumn will mean that the over winter rain will help dissolve and move the lime down through the soil, setting the finest portion of the lime to work on correcting soil acidity.

Delaying liming until spring will mean early grass growth on low pH soils will be compromised. The availability of phosphate is reduced when:

  • Soil pH is below 6.0
  • Low soil temperatures

This will have a double whammy effect on grass. Phosphate is essential for the growth of new grass tillers, root growth and the transfer of photosynthetic energy trapped from the sun into chemical energy which the plant can then use to grow.

The soil is full of organic nitrogen (N) which needs to be broken down (mineralised); however we rely on a host of different soil borne microscopic organisms to do this for us. These organisms are pH sensitive, and they prefer a soil pH above 6.0 for them to work effectively. Therefore, as spring progresses and soils begin to warm up these organisms begin to release a significant amount of N but only if the soil environment is right.

Applying slurry soon after the application of lime in the spring is not recommended due to the increased risk of ammonia-N volatilisation. The ammonium-N in the slurry reacts with the lime on the surface of the soil which then increases the proportion of ammonium-N converted to ammonia-N gas. By having the lime applied in the autumn, the farmer won’t have to juggle slurry and lime applications in the spring.

There is no doubt that lime applications are justified even in late autumn where there are instances of very low soil pH, but remember only if field conditions allow. There is no point in correcting one problem and creating another.

However, if ground conditions in the autumn don't allow travelling then lime can still be applied in early spring, and you will see the benefits the same season.

A soil test should be taken to identify if lime is required and how much. Do not apply any more than 5 tonnes/ha in a year even if the soil test result indicates a lime requirement of more than this. 

Find more information on soil testing

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