Use of Lime to Maximise Soil Nutrient Performance

May 13, 2020

Mary Ann Alexander, CAFRE Agri-Environment Adviser, Magherafelt

There are many benefits to spreading lime on farm. Lime is a soil conditioner and controls the soil acidity by neutralising the effects of acids from nitrogen (N) fertiliser, slurry and high rainfall. Other benefits include an increase in earthworm activity, improvement in soil structure and grass is more palatable to livestock.

Soil pH is a constraining factor on many farms in Northern Ireland. A survey conducted in 2014/15 by AFBI of over 500 field sites in Northern Ireland found that of the grassland fields sampled, 64% were below optimum levels for pH. Because of this under liming farmers could be losing 2t DM/ha/year of grass.

If a soil is not within the optimum pH range it can lead to other nutrients, such as phosphorous (P) and potassium (K), not being released at optimum levels. This means that a certain amount of fertiliser spread on farm would be wasted by the crop not being able to utilise it. Research has shown that up to 52% of phosphorus sown is lost if the pH is below 6.0. To counteract this farmers should develop a liming programme for their farm.

What is involved with a liming programme?

Developing a liming programme will provide one of the best returns on investment on the farm. The first step in developing a liming programme is to carry out a soil analysis. AFBI research has shown that investing in soil analysis is the most financial investment a farmer can make. If we don’t measure, we can’t manage!

Soil analysis results will highlight the pH of your soil for each field and the lime requirement. This is the total lime required – not the amount required each year. Although perennial ryegrass will grow over a range of pH levels its optimum performance pH is 6.0 to 6.5 in mineral soils and target a pH of 5.3 to 5.8 in peaty soils.

A liming programme for your farm should cover a period of 3 to 5 years depending on results. Target fields with highest lime requirement first, as these may need more than one application to raise pH levels. Also keep in mind that soils will need a maintenance lime requirement every 5 years or so depending on farm location and rainfall. It is good practice to apply lime to 20% of your farm on an annual basis. However, you should only apply lime based on a recent soil test report (within the last 4 years).

Where application recommended rates exceed 3t/ac, it may be more beneficial to split dress lime application at a rate of 2t/ac and apply the remainder in a year.

Farmers can lime all year round, however it is important to think of many factors when planning liming. We need to think around grazing, silage, reseeding, slurry and fertiliser applications when timing applications. The ideal time for applying lime is late summer/autumn as the ground is firm and silage cuts have been taken from fields.

The ideal conditions for spreading lime are on bare soils, for example after fields have been cut for silage or in fields that have been grazed down to low covers.

Key things to consider when applying lime:

•  If applying at reseeding time, incorporate well into the seed bed.
•  It is important not to lime swards intended for silage within 6 weeks of cutting depending on weather. This will affect the fermentation process and spoil silage in the pit.
• When slurry or urea and lime are to go on the same field – apply slurry or urea first then wait 10 days and apply lime.
• If lime is spread on a field you need to wait 3 months before applying slurry or urea to avoid the loss of N.
• On cattle grazing after lime spreading wait until rain has washed the lime off the base of the plant and onto the soil.
• With sheep grazing it is best practice to wait a full grazing rotation of around 30 days to allow for the lower grazing pattern of sheep.
• There should be no lime residue left on the grass before grazing for both cattle and sheep.

Applying lime is a simple and effective way to improve soils and grassland productivity on farm. It is something that every farmer should be considering and developing a liming programme is the best way to do this.

If you require any further information on spreading lime on farm your CAFRE Beef and Sheep adviser is there to help and can be contacted by phone on: 0300 200 7843.