When is the best time to apply lime?
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Ideally, autumn is the best time to apply lime when weather and ground conditions allow. Lime can take four to six months to correct soil pH, so an autumn application can set up grassland for growth next spring.
Quarry lime will typically have coarse, medium and fine particles, and these will break down at varied speeds before being available to adjust the soil pH to the required level.
Spreading lime in the autumn will encourage growth in the coming Spring by releasing organic Nitrogen and Phosphorous from the soil, encouraging earthworm and microbial activity, improves drainage, increased uptake and utilisation of chemical NPK fertiliser by grass plants and tillage crops.
Also, spreading lime in the autumn reduces the risk of lime being taken up in silage crops next year. Excess lime in mown grass will inhibit silage preservation, resulting in poor-quality silage.
Lime is the foundation of all soil fertility, grass growth and livestock production. Lime, along with phosphorus (P) and potassium (K) are all essential grassland nutrients that need to be maintained at optimum levels in order for grass and other crops to grow efficiently.
Lime is the cheapest of these vital nutrients, and unfortunately, it can often be the most ignored of them also.
A low level of lime on a farm and in individual fields in recent soil test, left unaddressed, will impact negatively on grass production in the coming years.
Adequate lime can have a huge effect on animal thrive, resulting in extra liveweight gain and allowing for higher stocking rates. Lime supplies calcium and, in some cases, magnesium, which is important for healthy bone development in livestock, for the production of milk, and to help reduce the incidence of grass tetany.
Lime improves grass sward quality. It is essential to correct soil acidity and facilitate healthy plant growth. Soil acidity is measured on the pH scale of 0 to 14. The optimum pH for good grassland is 6.3 to 6.5.
Ryegrasses and clover perform best at this pH or higher but are replaced by lower productive weed grasses, when the pH drops below 6.0. 60% of soils in the region have a pH less than 6.0. Therefore, keeping grassland close to pH 6.3 is essential to maintain Ryegrasses and Clover in grassland.
When reseeding grassland, lime increases the availability of nutrients (NPK) to grass seedlings. Any lime recommended on the basis of a soil test should be applied and tilled into the seedbed before sowing commences.
Liming promotes soil micro-organisms and encourages earthworm activity that break down plant and animal residues to release plant nutrients, especially Nitrogen.
Liming an acid soil has been shown to significantly improve the release of free Nitrogen from the soil each subsequent year for several years.
It also improves the availability of Phosphorous to plants and aids it’s release from organic matter. At a time of higher fertiliser prices, keeping soils at the recommended pH is a good investment.
With the application of lime, correcting the pH allows optimum use of other nutrients such as potassium (K).
Lime is lost from the soil mainly due to draining off of water. This loss is approximately 250 to 265kg per hectare/year, depending on rainfall, soil type and the amount of lime in the soil to begin with.
Growing crops and grazing livestock remove lime. An average crop of silage removes 60-80kg/ha/year of limestone. Nitrogen usage will also increase soil acidity; for example, each 1kg of N applied will require approximately 2kg of lime.
Completing a regular soil test is the first step in correcting any lime deficiency. A soil test will give the soil fertility status for pH lime requirement as well as phosphorus (P) and potassium (K).
- Brian Reidy is an independent ruminant nutritionist at Premier Farm Nutrition.
