SOIL ENRICHMENT Of all the influences on the growth of plants, the soil is one of the most important, and while it can be modified by various additives, its complexity is so great that the effects of the additives are only partly understood. As every site has its own microclimate and every plant has its own requirements for best growth, so every garden has its own soil characteristics. These characteristics must be understood so that the gardener can determine what plants are likely to do well, and whether the appropriate changes can be made to allow growing of some particular horticulture treasure. pH LEVELS The starting point for understanding the soil, for the beginning gardener, is a soil test. The first and easiest is the pH test that determines the acidity/alkalinity balance of the soil. The optimum range for most vegetables and culinary herbs is between 6.5 and 7.2; neutral is 7.0. Soils in our coastal regions have a low pH (they are acidic), especially where the soil overlies granite or where it is high in organic material, such as from a forest floor, a bog, or a former lake bed. NUTRIENTS The second test is for the amount of nitrogen (N), phosphorus (P) and potassium (K) available to the plants. These are essential nutrients. In coastal soils, potassium is usually high but nitrogen and phosphorus are inadequate for the intensive cultivation of some plants, particularly vegetables and some culinary herbs. ORGANIC MATTER A third test is for the organic matter in the soil. The amount of organic material helps to determine the number of microorganisms as well as the amount of nitrogen that can be made available to the plant. If the amount of organic matter is high enough -- about five per cent -- it enables the plants to take up phosphorus and potassium, which would otherwise not be available. Sandy and clay soils can be greatly improved with the addition or organic material. Soils high in organic matter warm up quickly in the spring, hold moisture well and, in general, provide an excellent medium for plant growth and health. The least complicated way of ensuring good soil conditioning in the coastal areas of the Pacific Northwest is to make some assumptions about average soil conditions. Average soils are too acidic for optimum growth of most plants, especially culinary herbs and vegetables, and they are too low in nitrogen and phosphorus. The simple answer is to add agricultural lime to beds in the fall, and to use dolomite lime in spot applications. Mix the lime in well with the soil. Add compost and use green manures to maintain or increase the level or organic mattter, and add nitrogen at critical times in each plant's life. Incorporate rock phosphate every three years in the fall to maintain adequate phosphorus levels. Trace element levels can be maintained by the use of compost and fish fertilizer and by maintaining the organic matter of the soil at a high level. Excerpted from A West Coast Kitchen Garden by Andrew Yeoman, Whitecap Books Ltd. ISBN 1-55110-279-X.

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