Gardening with clay soils
Presenter: Nigel Ruck
Episode: 23 (6th October 2007)
Nigel visited a housing development in Sydney’s north-west called Kellyville Ridge. The area is experiencing massive housing development and growth. There are a lot of new homes being built, therefore there’s plenty of landscaping to be done.
The soil in this area has a high clay content and on many sites the soil is stripped away in preparation for pouring the concrete slab for the house being built. In these cases what you can end up with is some pretty heavy duty clay that certainly presents its fair share of challenges. These problems include poor drainage and expansion and contraction is caused according to changes in moisture content, known as reactive clay, which can affect structures.
A good way to overcome the clay problem is to build raised beds. Building a retaining wall and bringing in new soil to get up above the heavy clay will improve drainage and create a better medium for the plants. It’s important when you’re doing this to integrate the new soil into the existing by mixing the two together. This improves drainage, allowing water to flow between the two more easily.
With the lawn areas, the clay subsoil has often been graded on a gentle slope and then new soil has been added to raise the area about 300mm, the slope is maintained to facilitate surface drainage. If you don’t have the room to build up the soil levels, some sub-surface drainage is a very good idea.
With the brick edging on some sites you could just lay the bricks on a bed of mortar but because the clay expands and contracts with moisture variation it’s better to lay the bricks on a footing.
If there is a fair amount of fill it is worth using concrete reinforced with steel bars for extra strength. The last thing you want is bricks to buckle if the clay moves. If you are placing the bricks on their sides there is the possibility that the grass will grow through into your garden beds.
In these cases it is worth putting a line of mortar on the side of the bricks.
If you are bringing in new soil it is a great idea to add plenty of organic matter and gypsum and really dig that through the soil. Gypsum is a natural clay breaker and combined with the organics the structure of the soil will be opened up, improving the drainage and oxygen and nutrient supply to the plants.
Episode: 23 (6th October 2007)
Nigel visited a housing development in Sydney’s north-west called Kellyville Ridge. The area is experiencing massive housing development and growth. There are a lot of new homes being built, therefore there’s plenty of landscaping to be done.
The soil in this area has a high clay content and on many sites the soil is stripped away in preparation for pouring the concrete slab for the house being built. In these cases what you can end up with is some pretty heavy duty clay that certainly presents its fair share of challenges. These problems include poor drainage and expansion and contraction is caused according to changes in moisture content, known as reactive clay, which can affect structures.
A good way to overcome the clay problem is to build raised beds. Building a retaining wall and bringing in new soil to get up above the heavy clay will improve drainage and create a better medium for the plants. It’s important when you’re doing this to integrate the new soil into the existing by mixing the two together. This improves drainage, allowing water to flow between the two more easily.
With the lawn areas, the clay subsoil has often been graded on a gentle slope and then new soil has been added to raise the area about 300mm, the slope is maintained to facilitate surface drainage. If you don’t have the room to build up the soil levels, some sub-surface drainage is a very good idea.
With the brick edging on some sites you could just lay the bricks on a bed of mortar but because the clay expands and contracts with moisture variation it’s better to lay the bricks on a footing.
If there is a fair amount of fill it is worth using concrete reinforced with steel bars for extra strength. The last thing you want is bricks to buckle if the clay moves. If you are placing the bricks on their sides there is the possibility that the grass will grow through into your garden beds.
In these cases it is worth putting a line of mortar on the side of the bricks.
If you are bringing in new soil it is a great idea to add plenty of organic matter and gypsum and really dig that through the soil. Gypsum is a natural clay breaker and combined with the organics the structure of the soil will be opened up, improving the drainage and oxygen and nutrient supply to the plants.
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