Doing Some Soil Testing In Your Garden

Published: 27th April 2009
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Calcium is important for cell-wall integrity and root and leaf growth. If you lime your soil regularly to keep the pH above 6, calcium deficiency would be unlikely. However, on alkaline soils (pH above 7) add gypsum (calcium sulphate) instead of lime. Low levels of calcium show as deformed new leaves and branches, and weak stems and roots.

Magnesium (Mg).

Magnesium is essential for chlorophyll and green leaf development. Pale leaves with green veins are a sign of deficiency. Adding dolomitic lime to raise the pH often corrects deficiency symptoms; on alkaline soils, add Epsom salts (magnesium sulphate).

Caution exchange capacity (CEC). CEC measures the ability of soil particles to hold and release specific nutrients. In general, sandy soils tend to have a lower CEC than most clay soils. Adding well-rotted compost raises the CEC. High CEC usually means a more fertile soil. If your soil has a low CEC, add small amounts of fertilizer throughout the growing season to prevent runoff and waste.

Organic matter is essential for nitrogen absorption and release, and as a food for micro organisms that help make other nutrients available. A level of 3 to 5 percent organic matter is considered ideal. But it's the quality, not the amount that can make the difference. Soils high in un-decomposed organic matter, such as wood chips or sawdust, can tie up nitrogen and create a deficiency. The best-quality organic matter to apply, especially right before planting, is well-rotted compost.

Percent base saturation.

Some experts consider the relationship between four key elements (calcium, potassium, magnesium, and sodium) an indication of soil health. The ideal ratio is approximately 60 to 80 percent calcium, 10 to 15 percent magnesium, 5 to 7 percent potassium, and less than 3 percent sodium. Adding these figures gives a number called the base saturation. In general the higher the number within the given ratios the more fertile the soil is. If you're adding bulk organic fertilizers such as manure, you can reduce the amount of other fertilizers by a third.

Do-it -yourself soil tests.

For a quick check, many home tests are available. These rely on colour charts to match the nutrient levels in a soil solution. Unless you buy an expensive test kit, the specific nutrient tests aren't, in general, as accurate as in a professional soil test but never the less they do equip you with a basic knowledge of your gardens soil. They give a guide of the pH and nutrients that are immediately available.

Acid or lime:

- Acid Soil does not have much - if any - lime in the soil. An Alkaline Soil does have lime in it - to varying degrees. A Neutral Soil will have lime in it, but not enough to class it as an alkaline soil. You can also do a basic test by drying a teaspoonful of soil, and then sprinkle some vinegar on it. If it bubbles, it will probably have lime in it. If is doesn't it will probably be acid or neutral!


Most plants need lime in the soil to live and thrive. Rhododendrons, Camellias, Ericas and a few others do not. They cannot flourish in soil where there is lime, in fact most will not just struggle to survive they will die!

Lime encourages soil life, for the bacteria that sorts out your organic matter into Nitrogen, are quite lethargic in acid soils.

Lime improves the 'tithe' (crumbly structure) of heavy soils such as clay soils. A really sticky clay soil can be put right quite dramatically with a dressing of lime. The lime coaxes the individual clay particles to form 'groupings, allowing moisture to drain, and plant roots the freedom to roam.

Lime can act, as a deterrent for some pests - slugs and leather-jackets are not keen on lime. It will also act as a preventative for club root in brassicas. Lime in the soil is good for earthworms. Most soils will benefit with a high earthworm population. As well as helping to break down raw organic matter, they make a network of drainage channels in the soil - great for heavy clay soils.

Find tips about growing ferns and asparagus fern at the Plants And Flowers website.

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