To choose the perfect soil to import to your garden you need to know:
History: The history of the soil you import determines if it will be suitable for growing crops. Agricultural top soil often contains residual herbicide. Soil from a coastal location may contain a high level of salt. Soil from a toxic site such as a demolished fuel station will contain diesel. A gardener can test soil for toxicity. A small sample can be placed on a windowsill; moistened and cress seed broadcast on it. The seed will germinate but quickly die back in the presence of: salt, residual herbicide or diesel.
Soil Type: You can test soil type by rolling it in your hands. If it sticks together in a ball it is clay soil. Sandy soils contain coarse particles you can feel them when you rub the soil between your fingers. Soil that sticks together and contains coarse particles is called a loam. It contains both sand and clay. Sandy soils are free draining. Loams hold nutrients better than sands. Clay soils can be difficult to work and they puddle (hold standing water).
Soil pH: The pH scale measures acidity / alkalinity. Most garden supply retailers will stock soil pH testing kits. A neutral pH is 7 generally food crops require a neutral pH. Some plants prefer acid conditions they are called ericaceous. Plants that prefer alkaline conditions are chalk or lime loving.
Purpose: To choose the perfect soil you need to know what you want the soil to do. If the soil is to be used as a medium to grow food crops; it will need to be free draining and have a neutral pH. Ornamental gardens can be acidic or alkaline. Heathers, azalea, camellias and rhododendron are examples of plants that an acidic soil sustains. Chalk, lime soils have a high alkaline value. Weigela, ceanothus, and photinia are examples of plants that we cultivate in areas of chalk or lime soils. Some gardens grow plants that need drier soil. Examples of plants in a dry garden are Perovskia; Russian sage, Rudbeckia and all kinds of Sedum.
Organic Matter The perfect soil will contain organic matter. Organic matter sustains soil life. Micro-organisms and small creatures that can live within soil are mostly beneficial. They need organic matter for food and habitat. The organic matter content isn’t crucial to choosing the perfect soil because a gardener can add compost or farm yard manure after the soil is imported.
Altering pH If necessary a gardener can alter the pH of soil. Leaf litter mulch or fertilizers containing sulphur are acidic. Lime is freely available and will increase the pH of an acid soil.
To choose the perfect soil the essential criteria are: will it be free draining and is it toxic. A gardener can improve the soil with; organic, mineral or chemical additives. It is important to identify a cultural theme within a garden if one exists. Then choose a sand or loam soil that is acid or alkaline appropriate to the garden destination.
Andrew Astle trained and qualified as an agricultural agronomist with Fisons/Boots Agriculture in the 1980s. He went on to grow flowers commercially and has grown fruit and vegetables on his own account for thirty years. He wrote the book “TINE” How to Garden Without Digging available at: http://www.soilisalive.com