Heavy Soil or Light Soil Which is the Best for a Dry Climate Garden?
 (Read 500+ times)
By Jonathan Yaakobi
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If you're still thinking about how to make a garden in your plot, and haven't actually started the work, and if you are in the situation where soil has to be brought in, no doubt you've been pondering about the most appropriate soil type for your future plants. Perhaps you've already consulted with a gardening contractor on this subject, or with a soil scientist. If so, there are all kinds of issues that you've probably discussed by now, such as drainage, soil fertility, the problems associated with soil compaction, to name a few.
However did you know that soil type can have a significant affect on the amount of water the garden will consume annually? Broadly speaking, there are 3 options. Clayish soil, known popularly as "heavy" soil, sandy soil or "light" soil and something in between, a soil type known as loam. A commonly held view, is that light, sandy soils make for preferred conditions, while clayish, heavy soils, for inferior conditions. This view has been promoted by many contractors, partly because it's so much easier and therefore cheaper to build and plant a garden with light soil. As a garden contractor myself, I happen to have plenty of experience on this matter! While many heavy soils can be really poor, and should be replaced if possible, many are perfectly adequate, and are actually to be preferred to sandy soils. Assuming there's satisfactory drainage, many of the other problems associated with them, such as poor aeration, can be dealt with by common horticultural techniques, such as adding large amounts of compost, mulching, and by adopting an appropriate irrigation regime.
The moisture retaining properties of clay determine that waterings should be relatively infrequent, but with proportionally larger volumes at each go. This is to allow air to fill the spaces in the soil, vacated by water as it drains away. And this is where water can be saved. For example, let's take a lawn in a Mediterranean climate, whose area is 50 m2. A typical evapo-transpiration rate for perennial lawns in this sought of climate could be 4mm per day. That's to say the lawn is taking up some 4 liters of water for every square meter per day. As sandy soils have poor moisture retention properties, the lawn (in sandy soil) could be watered every two days, to the amount of 400 liters. (4mm * 50 m2 * 2 days = 400). Yet on the other hand, in heavy clay soil, the interval between waterings could well be 7 days or more. That means the quantity to be used would be 1,400 liters.( 4mm * 50 m2 * 7 days = 1,400) Where's the saving you may ask?
So far, none at all. However if we use a lawn species suitable for a hot climate, a deep-rooting species like Zoysia for instance, and providing there's enough soil depth, say over 70cm, then we can take advantage of the way water behaves in clay soil, and the way it is retained, by extending the irrigation interval by say 1 day, while retaining the same quantity to be consumed. In other words instead of 1,400 liters every 7 days, we water to the tune of 1,400 liters every 8 days! During the long hot Mediterranean summer that can be a considerable saving.
What's good for thirsty lawns is even better for water conserving plants. In heavy soils many drought hardy shrubs and trees can be irrigated once a month, with very significant savings. Furthermore, when working with heavy soil, it can be possible to wait for rain in the in-between seasons, whereas under circumstances where plants have to be watered very frequently, as with light sandy soil, this is often not the case
WARNING: While light soil can be placed on top of heavy, heavy soil should never be placed on top of light soil. Also soil types should never be mixed.
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Author Bio Box: Jonathan Yaakobi
 My name is Jonathan Ya'akobi.
I've been gardening in a professional capacity since 1984.
I am the former head gardener of the Jerusalem Botanical Garden, but now concentrate on building gardens for private home owners.
I also teach horticulture to students on training courses.
I'd love to help you get the very best from your garden,
so you're welcome to visit me on http://www.dryclimategardening.com
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