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Guide 20
addition to P and K release from the soil, N supply worth
up to 75 may also be achieved, boosting spring growth in
particular. If this extra grass production is utilised by the grazing
livestock it has the potential to reduce farm feed bills by at
least 180/ha/year. One tonne of additional grass production
each year over a typical five-year liming period (5t/ha lime
applied) represents a 7:1 (grass 180/t: lime 25/t) return on
investment in lime, not including the potential for reducing
fertiliser costs into the future.
Management tips when applying lime to grassland
Apply lime based on the soil test report. Where lime
recommendations exceed 7.5t/ha it is best to split the total
application rate and apply up to 7.5t/ha initially and the
remainder in year three.
Do not over-lime soils as it will reduce the availability of
both major and minor nutrients.
Ground limestone is the most cost-e ective source of
lime. Ground limestone will start to work once it is applied
and is washed into the soil. The finer fractions of the
ground limestone will adjust soil pH upwards to
target soil pH over the shorter term (pH increases
should begin within three months) while the coarser
components will maintain this pH adjustment over
the longer term (12 to 36-month period).
Use magnesium limestone where soil magnesium
(Mg) levels are low (Index 1 or 2) to replenish soil
Mg reserves.
Maintaining soil pH will result in increased release
of soil N from organic matter up to a value of 75/
ha/year. This N release usually occurs in spring
and contributes to better early season growth
facilitating earlier stock turnout.
On heavier and organic soils there is often
hesitance about applying lime for fear of `softening
the sod' or increased poaching (due to rapid
breakdown of soil organic matter). On these soils, it
is best to apply lower application rates of lime (<5t/
ha) on a more regular basis to control soil acidity to
avoid `softening the soil'.
Wait seven days after applying urea or slurry before
applying lime.
Leave three months between applying lime first
and following with urea/slurry application.
Leave at least three months between applying lime
and silage harvest.
On grassland soils with high molybdenum (Mo)
levels increasing soil pH above 6.2 can lead to
increased Mo levels in the herbage. High intakes
of Mo in ruminant animals can lead to an increased
risk of copper deficiency. It is, therefore, recommended
to maintain soil pH at 6.2 on these soils or consider
supplementing animals with copper.
Granulated limes are a finely ground limestone (<0.1mm)
aiding the reaction with soil acidity to increase soil pH
in the shorter term. Recent research shows that these
products (usually used at much lower application rates
than ground limestone) are more suitable for maintaining
soil pH (ie. where soil pH is close to the target).
Apply lime as recommended on the soil test report.
Release soil nitrogen (N) for early grass growth (up 80kgN/
Increase the availability of soil phosphorus (P) and
potassium (K).
Grow an extra 1.0 to 1.5t grass dry matter per hectare
Every 100 investment in lime = 700 worth of extra grass