LIMING IN 2022 – A GREAT OPTION

By Glen Corbett, B&T Drystock Adviser, Teagasc Galway/Clare

One of the main focus areas of the Signpost Programme for 2022 is to help farmers improve profitability and reduce GHG emissions by spreading LIME to reduce chemical fertiliser use.

You can see from the following table that 2021 was a massive step forward in relation to lime usage with a 50% increase.

Even with the increase in lime usage, up to 50% of drystock soil samples are still deficient in lime. One of the big reasons that farmers, advisers and industry personnel have said that farmers don’t spread as much lime as they should is the lack of visibility of the lime industry.  There is an opportunity for spreading lime after 1^st Cut silage in the next few weeks. If you take action to spread lime this summer it will most definitely help reduce 2022 fertiliser bills.

Paddock Availability and Lime Residue:

Once fields have been grazed off or first cut silage has been removed, this is an ideal time to apply lime. (Note here only in cases where no second cut to be taken). Identify blocks of land that require lime from your soil sample results. Apply to low covers to correct low pH (target pH is 6 and over). Stock eating grass which has a lime residue can lead to them getting digestive upsets so this is where the low covers come in and typically some level of rainfall in the week following application will wash the lime from the leaf down to the soil.

Silage Fields:

A typical question we get is in relation to applying lime before cutting silage and also the relationship between applying lime and applying slurry about the same time.

So the rule of thumb is don’t apply lime in the calendar year on a field before you plan cutting silage on it.

In relation to second query - To minimise N loses from slurry apply cattle slurry FIRST, and then apply the lime 7 to 10 days later. Do not apply in the reverse order as it can result in a loss of up to 50% of the available slurry N.

It is a similar situation with Urea (apply straight Urea first, then lime 7-10 days later).

Lime & High Molybdenum Soils:

Soils with high Mo status may increase the risk of inducing a copper deficiency in grazing animals. On these soils increasing soil pH above pH 6.2 increases the availability of Mo in the soil and higher uptake of Mo by actively growing grass. Where farms are affected by high Mo soils maintain soils at or below soil pH 6.1 - 6.2. Alternatively, apply lime as recommended and supplement animals with copper.  Again look at soil results for this information

Speed of Reactivity:

Once lime is applied and is washed in it starts to adjust soil pH. At least 35% of ground limestone (350 kg/tonne) has a particle size < 0.15mm. This component of the lime is fast acting and very reactive and will start working immediately (0-6 months). The remaining 65% lime (650 kg/tonne) will be broken down in the soil in the medium term (6-24 months) and helps to maintain soil pH levels in the longer term until the soils are re-sampled in year 4-5.

So in summary the benefits of liming ground are there for all to see, just get the few basics right, as outlined. The release of soil N and the increase of soil P and K that liming brings about can’t be underestimated in these times of high chemical fertiliser prices. This in turn can lead to extra grass growth to the tune of 1.5t grass DM/ha. Which represents a return of €6 to €10 for every €1 spent on lime.