5
Lime
Lime is finely ground limestone, which is calcium carbonate. Lime is effective more quickly as a soil conditioner and to raise pH when it is finely ground.
Dolomite lime can also be used. It is a kind of limestone that contains magnesium as well as calcium.
Advantages of adding lime
- Adding lime makes acid soils less acidic. A less acidic soil will make more nutrients available to plant roots and therefore improve plant growth.
- Lime improves soil structure. When lime is added to clay soil, the tiny clay particles group themselves around the lime particles and together form larger particles. The process is called flocculation because it reminded someone of a flock of sheep coming together. Flocculation creates more air spaces, so the soil drains better. The soil is easier to cultivate and for roots to grow in. If humus is present, it binds the larger particles into crumbs and so produces a good crumb structure.
- Liming encourages the activity of soil organisms like earthworms and bacteria. Very acid or very alkaline soils reduce the activity of soil, which is needed to decompose organic material.
- Liming can make some nutrients more available to plants. For example, if the soil pH is above 6, phosphates are more available.
- Lime supplies calcium to the soil that is needed for plants' cell walls.
Applying lime
In a home garden:
- dig the soil
- sprinkle lime over it
- rake it into the surface layer of the soil
- water the soil with a sprinkler or hose
- leave the plot for two weeks before planting.
On a commercial property:
A truck, tractor or quad motorbike will be used to apply the lime. Aeroplanes are also sometimes used.
The amount of lime that is used depends on the:
- soil pH
- plants that are being grown
- soil texture.
Key points
Lime is considered to be a soil conditioner. It can be used to raise the pH of a soil to make it less acidic. It will also flocculate clay particles so they will form crumbs rather than clods.
In a soil with a pH of about 6–6.5 most minerals are dissolved in soil water and can be used by plants.
By adding lime to the soil, plant growth is improved because:
- nutrients are available
- soil structure is improved and therefore drainage and aeration is improved
- micro-organisms activity is encouraged.
What's next?
Go to: 6 Cultivation.