Grow more grass by applying lime
THE optimum use of fertilisers is obtained when soil pH is between about 6.2 and 7.2. However, more than 50% of soil samples show a shortage of lime so the first step in producing any crop is to get the lime status right.
Lime is a soil conditioner, meaning that it corrects soil acidity so that the micro-organisms can thrive and break down plant and animal residues. It helps in the release of Nitrogen and other nutrients from organic matter; and it increases earthworm activity, which improves soil structure and assists the growth of clover and the survival of Nitrogen-fixing bacteria.
SURFACE ACIDITY
Liming soils improves the availability of all fertilisers, especially nitrogen and phosphorous and many trace elements.
Surface acidity (in the top 50mm) often occurs in grassland due to our high rainfall and high usage of nitrogenous fertilisers. The result of this is that the availability of Phosphorous is reduced. To correct this it is better to have frequent small applications of lime than one large application. Keeping the pH above 6.0 in grassland improves Nitrogen recycling and reduces total Nitrogen requirements.
LITTLE AND OFTEN
In grassland soils which are high in molybdenum (Mo), it is important not to raise the pH above 6.2, as increasing the pH above this level increases the availability of Mo and this in turn induces copper deficiency in the animal by reducing copper absorption.
If the lime advice exceeds 3t/acre for grassland, only 2 tons/acre should be applied initially and the remainder after two years. Lime applications should be based on a recent soil analysis.
BEST TIME TO LIME.
There is no best time to lime, provided lime is spread evenly and left near the surface of the soil. Ground limestone can be spread any time and pasture fields can be limed in rotation. Grass can be grazed as soon as the lime has been washed off the leaves by rain. A large amount of ground limestone is readily available to the crop and benefits will happen fairly quickly with the remainder being broken down over the following few years. A five-year liming plan should be put in place on every farm.
Silage fields should not be limed until the final cut is taken.
LIME AND UREA
If lime is spread in spring don’t spread urea on that field till the following year
LIMING PEATS
Be careful when liming black, peaty land. The ideal pH for peat soil is 5.5.
BAG LIME
Bag lime is finely ground lime which is granulated and can be applied with a normal fertiliser spreader. It is very fast acting but is much more expensive than ground limestone. It is very suitable if small amounts are required to maintain soil pH, however if using bag lime it should be applied every year. It is also convenient when reseeding small amounts of grassland.