Applying agri lime is a sustainable and cost-effective way to improve soil fertility and grassland productivity on farm.
Due to our high levels of rainfall, Irish soils have a natural requirement for lime to control soil acidity and maintain a favourable soil pH for crop growth, nutrient release and soil quality.
Despite this, according to Teagasc research, currently only 50% of our national lime requirements is being applied, and 80 – 85% of our soils are testing sub-optimal for major nutrients such as soil pH, Phosphorous (P) and Potassium (K).
Lime can be applied throughout the year, provided soil and weather conditions allow. Take the opportunity to apply lime during the growing season and earlier in the year, as the back end of the season tends to be the wettest period.
It is important to take advantage of the benefits of liming, to use Nitrogen (N) more efficiently, to help reduce the total farm N requirement, while at the same time protecting the environment.
Lime is something that every farmer should be considering, and developing a liming programme is the best way to turn your intention into action. Based on ‘The Facts on Applying Lime’ fact sheet recently produced by Teagasc, we address the 10 most frequently asked questions by Irish farmers on the application of ground limestone.
1. When is the ideal time to apply lime on grassland?
An ideal time to apply lime is once fields have been grazed-off and grass covers are low. It is advisable to apply lime earlier in the year when soil and weather conditions are more favourable.
Identify blocks of land that require lime. It is recommended to order a load of lime (20t) after each grazing rotation to correct soil pH (covers approx. 10ac at 2t/ac lime application rate). Aim to avoid high grass covers > 800kg DM/ha.
2. How do I avoid lime residues on grass?
Ideally, apply lime to low grass covers to reduce the risk of lime residues. Rainfall will typically wash most of the lime from the grass down to the soil. Where a small amount of lime remains on the leaf, it will not affect grazing animals.
During April and August, grass covers on farms tend to be low (500kg DM/ha) and present a good timing for lime application.
3. How do I manage acidity levels on softer ground?
Soil types where a relatively thick (5-10cm) organic layer has formed above the top soil may be more prone to poaching during wetter period of the year. This organic layer holds a large store of acidity.
Liming these soils to neutralise acidity and raise pH will create favourable conditions for biological activity and the release of the nutrients stored in the organic matter.
As nutrients are released from organic matter, the resistance of the top few centimetres of soil to heavy trafficking may be temporarily reduced. To minimise these effects, apply lime on “a little and often basis” and improve soil pH in stages over time.
Do not exceed 5t/ha in a single application or apply split applications (2.5t/ ha) over several years.
4. What do I need to consider when applying lime on silage fields?
Leave sufficient time, ideally up to three months in dry weather, between applying lime and closing for grass silage. This will allow the lime to be fully washed into the soil.
If lime is transported to the silage clamp or picked up in the baled silage, it may affect good preservation conditions for the silage.
5. What is best practice when spreading lime and slurry?
Spreading cattle slurry on fields that have recently received lime and where the lime has not had sufficient time or rainfall to be washed into the soil, can result in a loss of up to 50% of the available slurry N.
Best practice is to apply cattle slurry first and then apply lime seven to 10 days later, this will minimise N losses.
6. Can lime and urea be applied at the same time?
Similarly to cattle slurry, apply urea first and apply the lime seven to 10 days later to reduce the risk of N losses, as where straight urea fertiliser is applied on recently limed land, increased N loss (ammonia-N volatilisation) may occur.
However, where protected urea is being applied, early trial work indicates that it is safe to apply protected urea to fields that have been limed recently.
7. How do I manage soils with high Molybdenum (Mo) levels with lime?
Soils with high Mo levels may increase the risk of causing 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 levels, maintain soils at or below soil pH 6.1 – 6.2. Alternatively, apply lime as recommended and supplement animals with copper.
8. How fast acting is lime?
Once applied and is washed in, it starts to adjust soil pH. At least 35% of ground limestone (350kg/t) 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 (650kg/t) 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 resampled in year four to five.
9. Why is lime worth the investment?
Research shows that liming acidic soils increases grass production by 1t/DM/ha. On a dry stock farm this is valued at €105t/DM and €180t/DM on a dairy farm. An application of 5t/ha of ground limestone to correct soil pH represents a cost of €25/ha/year over five years.
The return on investment from lime gives €4 -7 worth of extra grass for every €1 invested in lime.
10. Which type to use?
There are two main types of ground limestone that are available nationally – calcium and magnesium. Calcium ground limestone is most widely available, is fast acting and gives rapid pH adjustment, while magnesium is mainly available in the southeast of Ireland.
Your Grolime approved supplier will be able to assist you with the correct type and rate of application, following your soil test results.
What is Grolime?
Grolime is the certified trademark under which companies who meet necessary criteria are authorised to promote and sell their ground limestone. All Grolime certified companies are licenced by the Department of Agriculture, Food and the Marine (DAFM) to manufacture and sell ground limestone for use as a soil conditioner in Ireland.
All Grolime companies undergo independent twice-yearly testing for Total Neutralising Value, Moisture Value and Grading, in line with the national specification for ground limestone. Therefore, it is essential you source your ground limestone through a Grolime supplier.
To view the full list of Grolime approved suppliers click here.
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