Good soil is the basis of any good garden. If your soil is sandy or heavy clay, digging and amending it before planting can be critical to plant health.
Sandy soils need organic amendments to help them retain nutrients and water, which otherwise leach out quickly. Clay soils retain moisture; they need organic amendments to loosen them, making air, moisture, and nutrients more accessible to roots. For most garden uses, the best soils contain approximately equal amounts of compost, sand, and garden soil.
But which amendment works for your particular soil? And how do you work it into the soil?
A new book An Illustrated Guide to Organic Gardening (Sunset Publishing Corporation, Menlo Park, Calif., 1991; $7.95) can help. Its 96 pages include a 20-page guide to building and maintaining soils; the guide focuses on organic amendments such as the ones listed here, and on fertilizers such as bat guano, fish meal, and grape pomace.
Adding organic soil amendments
Step-by-step instructions tell you how to prepare a planting bed using the method illustrated above: you double-dig the bed, blend in compost or other organic matter as needed, leave the surface rough for two to five days to air it out, then break up clods and work to a fine texture.
Among the types of amendment you can use, the following six are commonest: Chicken manure. Retains moisture well, so it helps sandy soils. Offers one of the fastest, strongest nitrogen fixes available to organic gardeners, making it good for leafy vegetables. Limitations. It must be watered in well to prevent nitrogen burn. Has an unpleasant odor, especially when wet. Contains some salts, though less than steer manure.
Compost. Plant material decomposed through bacterial action. It helps retain moisture and nutrients in soil, and is a gentle, slow-acting fertilizer. Diminishes moisture content in clay, increases it in sand. Limitations: Pesticide residues can make it unfit for vegetable gardens. Peat. The residue of partially decomposed bog vegetation such as mosses. It contains coarse fibers that loosen clays but also retain moisture especially useful in sandy soils). Limitations., Its water repellent when dry; mix it thoroughly into the soil. Steer manure. Improves moisture and nutrient retention in sand; loosens heavy clay soil, Limitations: Contains salts and weed seeds. (Dairy manure, from pen-fed dairy cattle, contains less of both; its a better choice, if you can find it.) Tree bark. Although often used as a mulch, it can sometimes double as a soil conditioner (spade it in after using it as a mulch). Ground bark improves moisture and nutrient retention in sandy soils. Limitations: Unless treated, raw bark tends to bind nitrogen in soils, making it less available to plant roots. Wood ashes. Contain 15 to 32 percent calcium carbonate, making them pound for pound almost as alkaline as limestone. They can correct overacid soils. Best suited to sandy soils; they can make clay soils even heavier. Limitations.- Shouldnt be used around plants that require highly acid soil. Ashes can also damage germinating seeds and new seedlings.
And other useful information
A 26-page chapter discusses managing plant pests and diseases (with information on 13 beneficial organisms, including earthworms, honeybees, lacewings, and ladybird beetles), types of organic sprays and dusts Bacillus thuringiensis to summer oils), and a rogues gallery of 33 plant pests (aphids to wireworms, pictured in color) with advice on what to do about them. Theres also a 23-page guide to plants for organic gardens. 1