Q&A: Lime can increase grass 1-1.5t/ha of dry matter
Soil test results show that, on average, 65% of grassland soils are below the target pH 6.3 — and up to 80% of soils in some counties.
There has been a dramatic drop in the use of lime over the last number of decades, with lime usage only 50% of what it was in the 1970s and early 1980s.
Liming Irish soils is very beneficial, as our soils tend to be naturally acidic, and require regular lime application to maintain their productive capacity.
Recent research from Johnstown Castle shows that grass yields can be increased by 1-1.5 tonnes of dry matter per hectare per year, from liming acidic soils.
Increasing annual grass production has many benefits, from reducing the need to purchase expensive concentrate feed, to increasing the livestock carrying capacity of land.
A recent survey shows that the major limitations to applying lime are land availability during the grazing season, and trafficability over the winter, due to weather conditions.
Over the coming weeks, every opportunity should be taken to apply lime and correct low soil pHs, when soil and weather conditions are favourable.
Check recent soil test results for recommended rates of lime.
Apply a maximum of 7.5t/ha (3t/ac). Where more lime is recommended, apply the balance after two years.
Some soils tend to poach after liming, due to the breakdown of the old sod.
On these soils, apply a reduced rate of lime on a regular basis, and don’t exceed 5t/ha in a single application.
Firstly, applied lime can increase the loss of nitrogen to the air after slurry application.
If slurry is first applied, leave it a week before spreading lime.
If lime has been applied, avoid slurry application for three months (the same rule of thumb applied to urea N fertiliser).
Yes, an equivalent of up to 80kg of N/ha will be released for several years.
What effect will lime have on soil P levels on acidic soils (pH 5.0 to 6.0)?
Liming acidic soils will increase the availability of P for plant uptake.
Fine ground limestone (35%) will work relatively fast, and the coarse lime particles will react more slowly and help maintain soil pH for a number of years.
There is no need to leave a gap, with CAN or NPK compounds.
What is the target pH for grassland, where my land is in a high molybdenum (Mo) area?
Maintain a soil pH of 6.2 on these soils.
Now is a good time of the year, as it allows time for the lime to work, and reduces issues in early spring with slurry/urea applications.
Ideally, apply lime as recommended on the soil test report one year in advance of reseeding.
Alternatively, apply lime at the time of reseeding, and incorporate it into the seedbed before sowing.
Once lime is washed into the soil, it poses no risk.
Slight tainting to the grass leaves during dry conditions may cause slight scouring.
