The good, the challenging (rather than just plain Bad) and the ugly
Good aspects of clay soil are that it retains moisture very well, because of this characteristic, is
nutrient rich. To explain, clay particles are negatively charged, therefore attract positively
charged nutrients - calcium, potassium, magnesium, and water molecules. Because of their
small size, the available surface area in a given space is greatly increased, allowing for more
nutrients (which are positively charged) to attach to the grain surface and be available for
uptake by plants. This ability of soils to hold nutrients based on their negative charge is
known as cation exchange capacity. Clay and organic matter have high cation exchange
capacities, so having clay is not all bad!
Challenging aspects of having clay, are that it drains slowly, compacts easily, and is on the alkaline side of the pH scale. Care
needs to be taken not to walk over the same spot repeatedly ­ unless you plan a pathway that is built to handle the foot
traffic and will preserve the soil levels. Otherwise depressions may develop, that allow water to accumulate.
Ugly sides of clay will become very apparent if neglected - surface cracks will appear
in dry weather. Clay is really hard to dig when dry, especially if it has been compacted
over time. If soil compaction has occurred, it reduces pore space for water and air to
access, and naturally roots will have a hard time finding spaces to grow into.
If you can, spend the time and investment preparing the entire planting area, instead
of just preparing a hole for one plant at a time. Improving soil will result in the texture
being looser, allowing roots their space to grow and water to drain.
You will need - 2 parts organic matter (mature compost), 1 part clean river sand and a fair amount of manual labour, as well
as slow release organic fertilizer, to be used in the ratio prescribed by the manufacturer.
X 2
X 1
To incorporate organic matter:
Dig in organic matter into the top 30 cm of soil, the height of the newly prepared area will settle down over time, creating a
happy family of microorganisms that have a suitable environment in the more stable soil structure. Digging in organic matter
should be done more than just this once, aim to top up once or twice a year to keep the soil structure intact. The best time
of year to do this task is before the rainy season, as clay will become heavy to turn over and dig, and the soil is still relatively
dry at this time of year. Work clay in winter, allowing frost to work on breaking clay sods up into smaller workable pieces.
During the process of rehabilitating clay soil to be a more organic, avoid compacting the area.
How much organic matter do you need?
Firstly measure the area that will be worked, you will need about 10cm of organic matter and 5cm of sand if you had to
spread it over the area before digging in.
Let's say a 5m by 5m space, this will be 25m2 to rehabilitate
To convert the 10cm and 5cm depth of material to be added, convert to metres, by dividing by 100
To convert that to square metres, multiply by the area
10cm = 0.10m, therefore 25m2 x 0.10m = 2.5m3 of organic matter
5cm = 0.05m, therefore 25m2 x 0.05m = 1.25m3 of sand
However, calculating that you need a large amount of organic matter in order to rehabilitate your soil might send some of
us into a dead faint at the cost., no fear, planning one space at a time will also work. If you are thoughtful enough to have a
compost heap, then this will make the whole process easier, and probably more rewarding!

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