‘We need to spread 1-1.2 million tonnes of lime annually’

The power of lime is often underestimated on beef farms in Ireland. By correcting soil pH, it has the potential to increase grass production by unlocking nitrogen (N) and soil phosphorus (P).

Soil pH has a major effect on soil nutrient availability and farmers should aim to maintain mineral soils at pH levels of 6.3-6.5; peaty soils should have a pH of 5.5-5.8.

Speaking at a recent technical day – organised for the 14 beef farmers involved in the Teagasc Green Acres Calf to Beef Programme – Teagasc’s Mark Plunkett outlined the benefits and returns that farmers can avail of by correcting soil pH.

Lime can be spread at anytime throughout the year and livestock can graze pastures once it has been washed off the herbage. It is the most underutilised and the most cost-effective nutrient in Ireland; it costs €20-25/t.

Where are farms at?

While Mark acknowledged that there has been some positive progress – in the past three-to-four years – in terms of soil pH, he explained that there is a long way to go – especially on drystock farms.

“We have a big requirement for lime in Ireland to maintain our soils in that optimum zone. We’d like to be above a pH of 6.2 on mineral soils. That’s where we want to be in terms of nutrient efficiency and maximising grass production.”

Continuing, he said: “Approximately 43% of our soils are optimum for pH, but we still have 15% of our soils less than a pH of 5.5.

“On drystock farms, somewhere in the region of 10-11% of the soils are geared up to maximise grass production – at optimum levels for pH, phosphorus (P) and potassium (K). So, the other 90% are short in one or more of the major nutrients,” he explained.

“There’s a lot we can do by implementing a fertiliser plan, getting the lime right and working on Ps and Ks; however, it is a slow process and we’re not going to fix it over night.”

Touching on the quantity needed in Ireland, he said: “We need to spread 1-1.2 million tonnes of lime annually. Of all the three major nutrients, lime is where we are seeing the most improvements. Ground lime is readily available with 40 quarries around the country providing good-quality ground limestone.”

What are the benefits of getting pH right?

Research from Moorepark and Johnstown Castle indicates that by increasing soil pH from 5.2 to 6.4 – and using only lime – an average grass production response of 1t/ha (dry matter) was achieved. This is worth €105/t (dry matter).

There are two reasons why more grass can be grown when soil is at the right pH; there are loads of nutrients locked up in Irish soils.

By correcting pH, farmers can release N and, secondly, it increases the availability of phosphorus; by getting the pH right, farmers can unlock the phosphorus in the soil.

Image source: Shane Casey

“That’s what lime does for our soils; nutrient availability is increased. You are making N, P, K, magnesium (Mg), sulfur (S) and calcium (Ca) etc. more available that’s basically growing more grass.

“The nutrients that you apply in fertiliser, slurry or farmyard manure (FYM) are also used more efficiently as well,” he added.

Soil acidity and soil tests

Continuing, Mark said: “It controls the acidity. If you’re on very acidic soil and you are trying to build P with 18:6:12 or 10:10:20, you should really stop and ask: Is my pH correct?”

However, Mark also outlined that while farmers can reap the benefits of spreading lime, the overuse of lime should be avoided.

“If you head towards a pH of 7-7.5, you actually reduce the availability of some nutrients. Of all the nutrients that can be applied, I wouldn’t apply lime until I have a good soil sample taken [in the last three-to-five years].”

Before attempting to build Ps and Ks, a soil test should be taken and the pH corrected if needs be. Then, farmers can turn to increasing P and K indices.

In addition to Mark’s presentation on soil fertility management, MSD Animal Health’s Suzanne Naughton discussed animal health and vaccination with the 14 Teagasc Green Acre Calf-to-Beef farmers.