Growing plants in sandy soils is difficult, fertilisers leach away quickly. You can add compost, however this also is used up at a rapid rate adding clay could be the long term solution.
If you want to permanently improve the moisture holding ability of sandy soils, you need to look for a long term and cost efficient solution. Soil amendments can help turn the sand soil into a sandy loam, and the most efficient way to do this is to amend them with clay and compost, and the best type of clay use is Kaolin.
You often hear gardeners and horticulturalist talk about Loam or Sandy Loan. This is great garden soil, but what actually is Loam and how can you turn sandy soil into loam ?
Loam is usually broken down something like this.
- 40% Sand
So start by adding compost which will improve the silt, and then clay, you can use a kaolin or bentonite. The clay will help hold the compost in the sand. Wetting agent can also be added if you must.
Problems with Sandy Soil
The problems with sandy soil are numerous.
The ideal soil is often said to be a sandy loam, this is a soil that has a good mixture of sand and clay. It simply means that the large particle (sand) have small particles (clay) mixed in. A combination of good moisture retention and and soil that is light well aerated and easy to dig.
They lack organic matter and added organic matter breaks down very quickly. This means that the number of beneficial microorganisms is decreased. Adding humus improves microbial activity, helps retain moisture and also improves soil structure. By adding Kaolin you improve the ability of the soil to hold organic matter.
Sandy loam is also much better at retaining nutrients such as fertiliser and minerals. Sandy soils do not do this, so more fertiliser is used than in a good sandy loam.
You can overcome the problem of sandy soils simply by adding Kaolin as well as organic matter. By using Kaolin you will achieve a long term effect. How much do you need to use ?
A good starting rate is around 1/2 kilo per square metre, it is better to build up slowly so as not to add to much. Some gardeners reason that around 20% is the general starting point for sandy soils. Up to 30% in very sandy soils.
How to Improve sandy soils.
Applications rate will vary depending on the soil itself. In very sandy soils up to 10kg per square metre may be required, however this should be done in stages. An application of 1kg may be adequate in some sandy loamy type soils.
- Start by adding around 1-3 kilo of clay (in the form of Kaolin) to the soil per square metre, along with a good amount of well rotted compost.
- Choose a small trail patch to commence with to determine the best application rate.
- Monitor the effects over 12 months. You will notice that the amount of organic matter in the soil has increased and microbial activity is improving.
- After 12 months determine if you need to add more Kaolin.
- At the same time, add more compost.
- After this you will need to keep adding organic matter each year, however less and less over time.