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Soil Amendments

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Soil Amendments and How to Use Them

 (from West Coast Seeds)

A soil amendment is anything added to soil to improve its texture, structure, fertility or other qualities. The type of amendment that is used depends entirely on how the soil needs to be changed. Before you begin, test the pH of the soil. If it is too acidic or too alkaline plants will not be able to take up the nutrients. 


Agricultural lime is a pulverized rock powder made from chalk or limestone that is high in calcium. Dolomite lime comes from a different source and is also high in magnesium. Consider lime as the Tums for the soil that also adds essential minerals. West Coast Seeds recommends that we add lime to our soil every three years in this region and that we follow a three-year crop rotation that takes advantage of the soil as it becomes acidic again.

Year 1: leafy vegetables like lettuce and spinach and Brassicas—cabbage, broccoli, cauliflower, kohlrabi

Year 2: legumes—peas and beans and onions and squash

Year 3: tomatoes, peppers, eggplants, potatoes and other root crops. At the end year 3, lime the soil.

 Organic Matter

Adding organic matter to the soil is one of the fundamental principles of organic gardening. It feeds soil microbes, which in turn release nutrients into the soil, increasing fertility, adds body to the soil and helps conserve moisture. Add organic matter to the soil before planting.

 Glacial Rock Dust

This is a naturally occurring powder of minerals pulverized by the movement of glaciers which contains a broad spectrum of nutrients that improve soil structure, mineral imbalance and moisture retaining abilities. Add glacial rock dust any time of the year. Because the powder is very fine, do it on a still or rainy day.


This is silicate mineral containing 20% iron oxide, 7% potassium, and as many as 30 other elements. It loosens hard soils and binds sandy soils, regulates the release of nutrients in the soil and assists in moisture retention. If you have clay soil, don’t add sand, add greensand.

 Manure and Farm Waste

Bedding from animal stalls and manure are excellent sources of nitrogen and other nutrients but you need to let them rot completely because fresh manure can burn plants and stunt growth. Bagged manure comes prerotted. Mushroom manure contains primarily decomposed chicken manure.

 Alfalfa Meal

Alfalfa meal is a byproduct of the alfalfa growing industry and contains such a broad spectrum of nutrients that it acts as a low intensity fertilizer. Add it to compost or directly into the garden because it accelerates the breakdown of organic matter and fuels microbial activity.


Seaweed breaks down easily and releases a lot of potassium as well as a broad spectrum of micronutrients. It also contains growth stimulating hormones that lead to vigorous growth and good resistance to disease and pests. Kelp can be added as a mulch in winter or put directly into the compost pile. Make sure you leave it out in the rain for a few days and please don’t gather seaweed in March because you will destroy the herring eggs. Try using kelp-based fertilizers such as Kelpman which can be used throughout the year as a liquid or foliar fertilizer.


A fertilizer such as Complete Organic 4-4-4 will build strong plants with better resistance to disease and stress, and with larger and more abundant fruits or roots. Put fertilizer beneath each transplant but not in direct contact with the roots. The roots of the transplant will eventually reach the fertilizer but in their own time.