Farmers who spread lime on their farms report positive results according to Teagasc but there are key guidelines to follow to make the most from the investment.
High annual rainfall can lead to a large removal of lime from the soil each year, it says, and advises to spread 2.5 to 5.0 t/ha once every five years depending on geographical location and the levels of rainfall (i.e. typically higher rates may be required in the West).
It says that rather than applying the maintenance lime over your entire farm once every five years, it is preferable to cover 20% of your farm on an annual basis.
Which Lime to Use?
In Teagasc’s handy advice leaflet on spreading lime it details the different types available to farmers.
Calcium ground limestone is the most common form used in Ireland, according to Teagasc it is fast acting and has a rapid pH adjustment.
Magnesium (Dolomitic) ground limestone is slower to react according to Teagasc but has a higher liming value. It says it is a good source of magnesium for soils with low levels.
Granulated Limes is finely ground (less than 0.1mm particle size) and it is very reactive, Teagasc says. It advises to apply this as maintenance product where soil pH is in the optimum range.
Lime & high molybdenum (Mo) Soils
High levels of Mo in grass can reduce copper uptake in grazing animals.
Soils with a high pH, above 6.2, are more likely to have a copper deficiency and are at increased risk of having high levels of Mo.
The key to minimising the level of Mo in soil is to keep the pH between a range of 6.0 – 6.2, according to Teagasc.
Poaching and soil types
As the soil pH increases after the spreading of lime to permanent pasture the breakdown rate of the grass sod may also increase due to elevated biological activity.
On wetter and more poorly drained soils this may increase the risk of poaching occurring in the short term according to Teagasc.
To reduce the risk of ‘softening the sod’ lime should be applied at a reduced rate using a little and often approach.