Problem Soils

Problem Soils

Different ways in which certain problem soils can be tamed and converted into something useful –  though organic matter also plays a major role in this.


The soils that most people have problems with are the heavy clays. These, as we have seen, have a tendency to go rock hard in the summer and become like putty in the winter. As an old farmer friend of mine used to say, ‘All you do is break tools on it in the summer and change its shape in the winter’. That just about sums up clay. He also claimed that it only needed a black cloud to pass over it to make it unworkable!

The thing to remember about clay is that it holds a far greater amount of moisture and plant nutrient than you will find in a lighter soil. This makes it much better for gardening on, but you have to learn how to deal with it. The one thing you must never do is try to battle it out with clay; you don’t stand a hope of winning and you’ll have a miserable time gardening — people who like having their own way should steer clear of clay.

Problem Soils There are two very important features of clay that you must take advantage of whenever you can. The first is that the alternate action of freezing and thawing will break it down into a workable condition. The second is that wetting and drying will have just the same effect.

Most gardeners know that, by digging clay in the early winter, the weather reduces it to a fine tilth by the spring, admirably suitable for seed sowing. The wetting and drying trick isn’t nearly so well known but is really more important because we can use it throughout the growing season. This is especially handy after a crop has been cleared and the ground dug. If you try to beat clay into submission to form a seedbed, you’ll fail. Even a Rotavator will simply make the lumps smaller, it won’t create a tilth. After digging, though, if the land is left until it is drying out following the first lot of rain, you’ll find that, caught just right, it’ll fall to pieces at a touch.

Another point to bear in mind is that, even making use of the wetting/drying trick, clay should never be dug deeply except in the autumn when it has plenty of time to weather. Fetching great lumps of raw clay to the surface in the summer is simply asking for trouble. Keep all cultivations as shallow as possible at this time.

That is the short-term way in which to treat clay and other heavy soils. The golden rule with them all is never to try to cultivate them unless they are in a fit and dry condition. If, when walked on, mud sticks to your shoes, don’t touch clay. Leave it to dry out a bit more. All you will do when it’s wet, as we have seen, is change its shape. The long-term answer to clay is bulky organic matter. One sometimes hears people who don’t really know what they’re talking about say that organic fertilisers, such as hoof and horn, will put clay right. This is absolute nonsense. A material of that sort is being applied at a few ounces per square yard. Bulky organic matter, such as garden compost, is the only answer and we’re talking in terms of several pounds per square yard. The more the merrier. This will open up the clay physically by introducing new and softer material to it which will eventually break down into humus, the miracle chemical.

Humus alone isn’t sufficient, however. We need the strawy and stalky material to open it up physically so that water drains away better and the clods are reduced in size. Added to this physical effect on the clay, some forms of bulky organic matter, when they have rotted down, will add to the ground quite useful amounts of plant foods.

On clay soils, any form of bulky organic matter (usually garden compost or farmyard manure) should be dug into the vacant vegetable plots during the autumn. This will give the clay all winter to weather and will help to improve the drainage during what is usually the wettest part of the year. That is the normal way of adding organic matter to the ground but another system, though seldom used amongst vegetables, is as a mulch.

There are several things which will not improve clay at all. The first is the addition of gravel or sharp sand on anything but a very local scale. The amount needed to do any good to a reasonable depth is so enormous that the cost prohibits it. Just to give you an idea, to improve the top 6in (15cm) of soil, you would need to work in at least a 2in (5cm) layer of sharp sand, and preferably more. The best way to use proper garden sand (not building sand) is to mark out exactly where the rows of seeds are going to be sown and sprinkle the sand along this. It can then be raked into the top inch or so prior to making the drill and sowing the seed. This will greatly improve the condition of the soil in which the seeds have to germinate and none of the sand will be wasted.

The other ‘don’t’ is in connection with peat and much the same rules apply as to sand. By far the best way of using peat (preferably sedge, used potting compost or old growing-bags) is to spread it along the sowing or planting rows and work it into the surface. Personally I’d rather use peat than sand. The next problem soil is completely the opposite to this.



The main trouble with a sandy soil is that it doesn’t retain water or plant nutrients for more than a short time. This tends to make sandy soil starved and dry. It is, though, excellent for growing vegetables in, especially root and salad crops. Provided that they are given sufficient water and feed, they thrive on sand. The coarse texture of sand makes it easy for roots to penetrate and, th us, for transplants to establish quickly. It can be cultivated in any way you like under all conditions except when it’s actually frozen solid!

In spite of these virtues, it is a difficult soil to get the best from, as a lot needs to be put into it, both materially and by way of work. The main aim of anyone gardening on sand must be to do everything possible to increase the water-holding capacity of the soil, and hence the nutrient level. Here, we come back to our old friend, bulky organic matter. As with clay, the best way of incorporating it into the soil is by digging it in but, and this is important, digging should be left until just before you want to use the land in the spring. The last thing we want to do is sharpen (increase) the drainage by breaking up the soil and adding drainage material in the autumn.

In fact, sandy soil should normally be left undug during the winter so that it can retain as much moisture as possible. Also, after digging, tread the land down firm again as soon as you can to reduce evaporation as far as possible. Much the same goes for any cultivations carried out on sand; it should be firmed back again soon afterwards.

Apart from the obvious need to water vegetables growing in sandy soil regularly, there is also the business of feeding them. In addition to the normal base dressing of fertiliser given before sowing or planting, a top dressing should be given about halfway through the plant’s life, or when peas and beans start cropping. To reduce the inherent acidity of sandy soils and to improve the nutrient uptake in the plants, you will need to lime the ground periodically during the winter.



The only other tricky soil present in large amounts in the UK is that overlying chalk. As was said earlier, this is often thin and starved and the main job a gardener has is to increase its useful depth to I 2in (30cm). You should never try to do this all at once because, if the soil is overlying solid chalk rock, all you’ll do is ruin what you have already got.

The way to tackle the job is by double digging the ground so that the topsoil and subsoil remain in separate layers. By incorporating garden compost or manure into the bottom layer, its fertility is built up over the years and it becomes useful to plants. When digging a chalky soil, always be careful not to fish up great lumps of raw chalk; too many of these will make it impossible to reduce the soil to a suitable tilth for gardening in.

Bed System

There are, of course, occasions, usually when the soil is heavy clay, when an alternative to back-breaking labour is called for. At such a time, the ‘deep bed’ system of cultivation usually provides the answer. There’s nothing mysterious about this and anyone can set it up. In its simplest form, it is just a series of beds with paths between them rather than one large area of cultivated land. In fact, bed systems of one sort or another have been in use for hundreds of years on a more commercial scale. The whole point of these beds is that, once they are established, they are never walked on at all; the paths between them are used for everything. This means that the soil in the beds stays in an open and workable condition the whole time. Its structure is never under threat and can go on improving year by year. The only hard work is right at the start when the whole area to be taken up by the beds is double dug. This is necessary to establish a good foundation to the beds, especially as regards drainage.

During the digging, garden compost or manure is incorporated into both the top and bottom spit (layer) of soil. Inevitably this will cause the soil level to rise but, if done before Christmas, it will have settled back by the spring. Then, in about March, the area is marked off into beds 4ft (1.2m) wide, 18in (45cm) paths between each. These paths will be used for all walking, working and picking so that the beds are never trodden on.

Another innovation in the bed system is that, because they are only 4ft wide, root crops such as carrots and turnips can be sown broadcast rather than in rows. This gives a far greater crop for a given area. If you don’t want to give the whole bed up to one particular vegetable, you just put down as much as you want and keep the rest for something else, or for successional sowings.

Another trick is to have the rows running across the beds instead of along them; this is another way of getting heavier crops from a given area. Spacing can also be tighter. If the recommendation for leeks is, say, 6in (15cm) between plants and 12in (30cm) between rows, this can be brought to 8x9in (20x23cm) because you don’t need the wider row spacing for walking in.

You’ll notice, though, that the result of multiplying the two plant and row spacings in imperial measurements come to the same, ie. 72sq in. This is because each plant still requires the same amount of space to develop fully; it’s just that the 8×9 row spacing is far neater and more convenient for the bed system. Remember also that, where the plants in a row are staggered with those of the previous row (each plant is opposite a gap rather than another plant), the spacing between the rows can be the same as that between the plants within the row. This is particularly useful for cabbages and cauliflowers, but take care not to ‘lose’ one plant in alternate rows.

If the preparations were thorough and the ground was well enriched with bulky organic matter, the beds should last for 3-4 years without further deep digging. They should, however, be lightly forked over incorporating garden compost, after each crop and given fertiliser in the usual way.

Double Digging

The system of double digging reduces drastically the amount of deep cultivations needed and makes the best use of the available space. It is not the same as the deep compost, no-digging bed system that is sometimes practised by, mainly, organic gardeners.

The really keen gardener who likes early crops can tilt the beds to the south by up to 10 degrees so that they catch the maximum amount of sun and warm up quickly. In areas of high rainfall, the tilting can also help drainage but a greater benefit in this respect is to have the beds raised a few inches above the paths. Remember to wear boots, though — the paths may be under water for much of the winter!


04. March 2011 by admin
Categories: Soil Cultivation | Tags: | Comments Off on Problem Soils


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