What are the benefits of using Lime or Gypsum?
Firstly, they improve the structure of the soil. The addition of calcium will bind the clay particles into soil crumbs. It’s a plant food. Plants need calcium like humans, they just benefit from a moderate amount. The addition of Lime or Gypsum will unlock nutrients that are trapped within the soil that will help the plant thrive. Lime in the soil can reduce the number of pests in the soil. You’re less likely to see slugs, wireworms, and club root. As very few plants like to grow in acidic soil, Lime can help neutralize its impact, making the soil more habitable for bacteria, and earthworms.
What’s the difference between Lime and Gypsum?
Let’s look at Lime first.
Lime (either calcium hydroxide or calcium carbonate) reduces the acidity of the soil by neutralizing the acid reactions in the soil. There are also different types of Lime that react with the soil at different speeds and have different Neutralising Values or NV. The number that is expressed alongside the Lime is a percentage of the pure calcium oxide.
- Chalk and Ground Limestone are slow acting and have an NV of 50-55.
- Ground Magnesian Limestone also known as Dolomite Limestone has an NV of 56.
- Calcified Seaweed is a long-lasting Lime and has an NV of 44.
- And Hydrated Lime is the strongest and works the fastest with an NV of 70.
If you need to use Hydrated Lime, always use gloves, and wear safety goggles, as this product is an irritant to the skin.
How much Lime do I need to use?
Before you start make sure you know:
- Your soil pH level.
- Your garden square meterage.
This is important as you need to know the amount you need to use and whether you need to dig into the soil or whether you can sprinkle on the surface.
The general rule is less than 0.5kg per square metre you can dig in, but if it’s too difficult then sprinkling on the surface is fine. If it is greater than 0.5kg per square metre, then dig half of the Lime into the soil and the rest onto the surface.
Always read the packaging carefully before you buy or apply.
What about Gypsum?
Gypsum (calcium sulphate) will add calcium to the soil without neutralising the soil acidity. So, this is ideal if you are looking to grow acid-loving plants like camellias, heathers, rhododendrons, or blueberries, in your clay soil.