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The Makings of a Good Top Soil – Part 1

Growing Onions

In any planting situation, be it in a general garden bed; under a lawn; in a vegetable or herb garden or even in a larger planter box or podium planter, there are some key requirements that plant life needs to thrive: sunlight, water and nutrients.

When considering a soil or planting media for all the above situations it is critical that the mix has the following capabilities and it is around these basic but critical capabilities, as well as many others, that the Australian Standard for Organic Garden Soils has been developed. AS4419. Over the next few blogs we will try to explain and outline the makings of a good top soil and what you, as the avid gardener should be looking for!

Stability & Substance

Perhaps the first and most simple of jobs a planting media or top soil needs to perform is to “anchor” the plant in the ground, especially if the variety is one that will grow to a reasonable size. If  planted in a mix that is too light and doesn’t have enough actual soil or mineral content in it, a large shrub or tree may blow over in high winds.

Open & Free Draining

Now it’s all very well to have a heavy soil that will anchor the plants in the ground but a second key requirement of the soil mix is that it is an open and free draining material so wont get waterlogged during wet periods. The ideal here is for the planting mix to be a blend of natural soils (or simply “dirt”) and sands with different forms of composted organic matter that result in a well drained soil. The reason the plants need their environment to be free draining is because the  root system not only needs to take water and nutrients from its surroundings but also oxygen and in a waterlogged situation this cant happen and the plant may “drown”.

Water Retention

While a well drained soil is essential, the danger is that if it is too loose and open with water passing straight through the mix, the plants are in danger of drying out completely and possibly dying. Getting the balance right between good drainage (permeability) and water retention will result in the soil environment being a healthy one where the plant is given the best chance to thrive.

Check out our next blog post to learn more about top soil and how choosing the right mix is critical for the success of your garden.

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