If you missed the first part of “How To Improve Your Garden Soil” please CLICK HERE to read part one.
Drainage will need to be at closer intervals on the heavier soils. On really heavy ones, it may make little impact as any drainage channels opened may soon close. On light soils, it can be widely spaced, needing only to bypass some impediment.
Drainage can be carried out by placing clay pipes or plastic drainage tubes in a trench, which is filled with coarse gravel. A layer of matting over the top will prevent or slow down the rate at which material falls into the trench and clogs up the gravel or pipeworks. Great care must be taken to ensure that the drains are not expected to run uphill, or they will quickly be blocked by silt.
On some soils, drainage can be effected by making slits in the soil and filling these with sand. Provision must always be made for the water drained to be taken off site. Except on a small scale, laying a pattern of drains is best left to a professional drainage contractor. However drainage is carried out, do not expect it to last indefinitely and any scheme will need to be cleaned or relaid at intervals.
Cultivation and drainage are the only two methods to significantly increase the depth of soil available for rooting but the quality of the soil can be improved by incorporating manures and composts into the soil. The organic matter added will benefit the soil structure of both clay and sandy soils, as discussed above.
Also the nutrients present in the manure will be added to the stock in the soil. The material can either be left on the surface, relying on earthworms and other soil organisms to take the organic matter into the soil (and for the rain to wash in the nutrients), or dug in by some form of cultivation; the latter will be quicker in effect.
Adding organic matter to poorly drained soils can lead to a decrease in fertility. This is because the organic matter can take what little oxygen there is out of the soil as it breaks down, leaving it anaerobic and make it turn even more sour. On heavy soils, manures should be used in association with other practices.
Raw material like straw can be used; it will take longer to break down into useful humus, and whilst it is doing that it will remove nutrients, primarily nitrogen, from the soil. It is a cheaper option than manures (where there is time to wait for the material to be broken down) for plants which are not sensitive to temporary low levels of nitrogen, or where nitrogen is also added as an inorganic fertiliser.
Organic mulches are similar to manures in their effect upon the soil, but are slower. They do not, however, contain any significant quantities of nutrients. Their effect upon soil structure is two-fold: by increasing the level of soil organisms, they lead to an improvement in the organic matter content of the soil, and by covering the surface they prevent compaction and the closing of worm burrows.
Chemicals can be used in three ways to improve soils.
Artificial or inorganic fertilisers can be used to supplement the nutrient supply. Specific deficiencies can be treated this way very quickly. Special formulations of fertilisers are available which can give a slow release of the nutrients. However, these are expensive and the role of fertilisers should be seen as replacing those missing after the soil has been improved, rather than as solving the problem.
Altering the pH of the soil can be of benefit. It is much easier to increase the pH of an acidic soil, such as by the addition of limestone or dolomitic limestone. Reducing the pH can be done by adding flowers of sulphur, and will occur if ammonium sulphate based fertilisers are added over a period of years. The effect will be to alter the availability of several nutrients, as discussed above.
On clays, chemicals can also be used to cause the clay particles to flocculate, or stick together in small clusters. Thus the soil becomes less sticky and more manageable. Lime is often used for this purpose and provided the plants you are planning to use are not affected by increasing the pH, it can be an effective way to improve such soils. Alginates, made from seaweed, can have the same effect.
Please CLICK HERE to return to read part one of “How To Improve Your Garden Soil”.