Land Management & Natural Hazards Unit	SOIL
European Commission	Joint Research Centre	Institute for Environment and Sustainability		EU Soils Web Site
Soil Atlas of Europe

Introduction

The soil in your garden The closest most people ever get to soil is when they are in their garden. Without soil, no flowers would grow, there would be no grass for the lawn and no fruit or vegetables for the kitchen! How does someone find out what type of soil they have in their garden? As you have seen in the previous pages, soil is made up of humus (organic matter) and various proportions of three different sizes of particles: clay, silt and sand. The particular combination of soil particles and organic matter, together with the local climate, parent material and previous vegetation cover determine the type of soil in your garden. A loam, which is a mixture of sand, silt and clay in rougly equal proportions with a moderate level of organic matter, is often regarded as the perfect garden soil! Topsoil When you look at bare ground, all you see is the topsoil. As you have seen in the previous pages, you'll see a clear boundary between the topsoil and subsoil if you dig a deep hole in your garden. Around a new house, it's possible that there will not be any topsoil at all. In this case topsoil must be brought in. It's worth checking this because if the topsoil layer is only a few centimetres thick, the subsoil can cause the gardener problems. What kind of soil do you have? Stand by a patch of bare soil in your garden with a watering can. Tip the water on to the soil. If the water drains away immediately, then you have a permeable soil. If the water lies on the surface for a while then the soil may be clayey or compacted. You can also find out what kind of soil you have by touching it. Take a good handful of soil, moisten it and squeeze it in your hand. If you are left with a ball of sticky material then you have a clay soil. Sandy soil feels gritty and falls apart when you open your hand. A peaty soil feels spongy while a loam or a silty soil feels smooth and stays in a ball but not as strongly as the clay soil. Another test for soil type is to see how the soil particles settle in water. Take a large transparent glass or plastic jar. Add a handful of soil, stir well and leave to settle over night. How the container appears in the morning can reveal the texture of the soil:	Neutral soil, usually clays, has a pH of 7. Acid soil, such as peat, has a pH of 6 or less while alkaline soil, often found in lime-rich areas, has a pH of 8 or more. The acidity of soil influences the plants that will grow in your garden because the pH level of the soil determines how plants absorb nutrients and control the presence of toxic elements. In alkaline soil, a number of key elements such as iron, manganese and zinc become soluble (dissolved in water) and are washed out of the soil while the levels of certain metals, such as molybdenum, become higher. In acid soil, aluminium and iron are soluble in sufficient quantities to be toxic to the growth of plants. Most plants prefer a pH between 6.5 and 7 (slightly acid or neutral). Within this range, nutrients are most easily available to plants. Plants that prefer acid soil conditions will not thrive in alkaline soil, and may even die. The opposite is also true. Plants such as rhododendrons or camellias growing in the garden indicate acid soil. Saxifrages, yew trees and certain clematis indicate alkaline soil. Whilst several conditions, including sunlight, water and soil acidity can affect the colour of flowers, in general, acidic soils produce blue blooms in hydrangeas whilst alkaline soil makes them pink. A more accurate way of establishing the pH of a soil is to use a testing kit, available from garden centres.	Improving the soil in your garden. Very few people are lucky enough to have "the perfect" soil in their garden. Many people have a heavy clay soil or nutrient poor sandy soil. There are a few simple ways to improve the quality of the soil in your garden. Digging and incorporating well-rotted organic matter can significantly improve soil structure. The easiest source of organic matter is a compost heap where garden waste (grass cuttings, leaves, twigs, straw) can be stored. In the case of a clay soil, sand and organic matter can be added to improve the texture of the soil. In many cases, the soil can lack sufficient nutrients. Plants do not grow very well. In this case you may need to add some fertilizer or "plant food" to your soil. Fertilizers are basically divided into two groups: Organic: from natural sources like plants, animals. Inorganic: manufactured 'chemical' feeds or mineral deposits. Plants don't care where their nutrients come from but from a gardeners' point of view, organic fertilisers have an advantage because they encourage soil bacteria, which help to keep soil healthy.
Sandy Soil: sand particles have sunk to the bottom and the water is clear. Silty Soil: water is cloudy, thin layer of sediment on the bottom. Clay Soil: water is still cloudy, very little sediment on the bottom because clay particles take a long time to settle. Loam Soil: fairly clear water, layered sediment on the bottom with finer particles on the top. Organic Soil: organic material floating on the surface, water cloudy and a small layer of sediment on the bottom. Lime-rich soil: layer of white gritty fragments on the bottom, water has a pale-grey or milky colour. What problems will your soil cause? If you have a clay soil-water logging when it's wet. If you have a sandy soil -drying when it does not rain. If you have a lime rich soil -dry and some plants will not grow in your garden. Is your soil acid? An important property of a garden is whether the soil is acid, alkaline or neutral. From a chemical point of view, the acidity of a soil is determined by the number of hydrogen atoms (ions) compared to hydroxyl ions (a compound of oxygen and hydrogen - OH). High levels of hydrogen ions causes acid soil while the reverse gives alkaline soil. Equal concentrations of hydrogen and hydroxyl ions give a neutral soil.

Page 18
Previous Page		Next Page
	Contents Page