Recognizing Your Gardening Soil

gardening soils

Understanding Your Gardening Soil

Soil — a complex mixture of disintegrated mineral rock, organic remains, air and bacteria — is literally the foundation on which any successful garden is built. Whether you grow flowers, grass, shrubs and ornamental trees, or vegetable and fruit crops, strong vigorous plants need good soil to thrive and perform well. Soils vary, however, and while fertile, moisture-retentive but well-drained loam is considered ideal, most soils can benefit from basic improvement.

Understanding your gardening soil type is the key to this, and to choosing the most compatible plants. Simple gardening soil-testing kits can assess acidity and alkalinity; other equally simple tests can determine soil texture and water content. From there, it’s an easy step to correcting chemical imbalances and improving structure and drainage if necessary.

All gardening soils benefit from regular enrichment to maintain their fertility and moisture content. Bulky organic matter such as well rotted manure, garden compost, leaf mould and spent mushroom compost add both vital humus and food. These are environmentally far preferable to the heavy use of chemical fertilizers, which add nothing to soil structure and can build up to harmful levels in the soil. Slow-acting organic fertilizers such as bone meal are beneficial in moderation. Peat has no value as a fertilizer and is in very short supply. It should be used sparingly.

Organic matter used as a surface cover, or mulch, provides extra benefits: mulched soil requires less weeding, and less watering in droughts. Mulch is also a natural insulator, keeping roots cool in summer and warm in winter.

Recognizing Your Gardening Soil

gardening soil Once you know your garden soil type, you can do much to improve it and maintain it in good health to give plants optimum growing conditions.

Not all plants will grow well in the type of soil in your garden — soil type varies widely and there is little point trying to alter it. However, once you have found out what type of garden soil it is that you have, there are many ways it can be improved. The better the soil, the easier it is to grow a variety of beautiful and productive plants.

Knowing Your Gardening Soil

To improve a soil you must first identify whether it is basically chalky, clayey, sandy or a mixture. You can find out a lot about the soil in your area by talking to neighbours and by working the soil yourself. Most libraries also stock copies of The Soil Survey of Great Britain which can give you much more detailed information.

In addition, consider soil-testing for chemical content and acidity/alkalinity. You can buy kits that are easy to use and give reasonably accurate readings. It’s a good idea to get one jointly with a friend (with different gardening soil) so you both benefit.

Your garden soil will fall roughly into one of four categories:

Chalk Soils

Chalk soils, formed from the breaking down of limestone, are strongly alkaline. Fuchsias, pinks and alliums thrive on them, but acid-loving plants such as azaleas, rhododendrons and most heathers hate them. These soils usually have little topsoil — you’ll hit bedrock quickly if you start digging — and are poor at retaining both water and plant nutrients. This means you need to keep on applying organic matter and fertilizers frequently.

Clay soil

Clay soil is made up of minute mineral particles that tend to clog together. It is probably heavy and sticky to dig since clay soils are generally poorly drained and aerated. When clay dries out, it sets rock-hard and cracks. To make the most of its natural fertility, you need to improve drainage and aeration by working in leaf-mould, shredded bark or horticultural grit, so that the texture becomes more open.

Sandy Soils

Sandy soils are light and easy to work. Although they warm up quickly in spring, giving plants a good start, they are so free draining that nutrients are washed out. Like chalky soils, they need plenty of organic matter and liberal dressings of fertilizer.


You are lucky if your soil is a well-drained loam, containing a good balance of clay and sand particles and a high humus content. Loams are the most easily cultivated of all soil types and hold water and nutrients well.

Acid and alkaline soils

The ideal gardening soil, a fertile, moisture-retentive loam, is slightly acid. Acidity or alkalinity is measured on a pH scale. Something neutral, such as pure water, measures 7. Anything above that is alkaline, below, acid. A pH reading which is between 6.5 and 7 suits the widest range of plants. Moderately acid gardening soils measure about pH6, moderately alkaline soils about pH7.5.

Sour (extremely acid) soils are often found in town gardens, and can be corrected with garden lime. Use 200g (½ lb) per sq m (sq yd), depending on how bad the problem is. Hydrated lime, available from garden centres, is the most convenient form.

Slight acidity is, however, preferable to a strong alkaline content — it’s much easier to modify. A bucketful of peat per sq m (sq yd) will increase the acidity of alkaline soils but, as peat has become an endangered commodity, reserve this treatment for the worst afflicted areas of soil. Plants on alkaline soil often show poor growth because they are unable to absorb trace nutrients such as iron and manganese. If you have alkaline soil, and still want to grow acid-loving plants such as azaleas and rhododendrons, the best solution is to create raised beds of acid soil, or to grow such plants in containers filled with an appropriate soil mixture.

28. October 2010 by Dave Pinkney
Categories: Garden Management, Soil Cultivation | Tags: , , | Comments Off on Recognizing Your Gardening Soil


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