Benefit from applying lime to grassland now

Benefit from applying lime to grassland

Correcting soil pH should be a priority for all livestock farmers. Investing in correcting your soil pH should deliver impressive returns as it will provide the right environment for your ryegrass and clover to reach its full potential as well as delivering numerous other benefits such 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

Independent research undertaken by Teagasc 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 winter rain will help dissolve and move the lime down through the soil allowing the lime to do its work in 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
• Soil temperatures are low

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, protecting their investment, grass growth and the environment all at the same time.

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.

What type of lime should you use?

Not all limes are created equally. The key is to know how much you need. The choice is really between a granulated lime, which reacts quickly to neutralise acidity or bulk lime, which is a more persistent liming material. If you’re working in less than ideal soil conditions and want to prevent soil compaction, granulated lime is convenient as it can be spread using a fertiliser spreader. However, it is more expensive than the alternative so it’s probably best to go with this option if you don’t need too much and the soil conditions are not ideal.

If you are operating in dry conditions where soil compaction is less of an issue and/or you need to apply a large amount of lime, the bulk lime is probably the best option for you.

One last tip

At a time when inputs are so high, don’t miss out liming if your pH is too low - it will undermine any further investment made in mineral fertilisers. By optimising your pH you will also make available nutrients that had been previously locked away from plant accessibility. Always start with your soil pH before adding more nutrients, otherwise you’re throwing money away.