Applied correctly, a soil additive conserves moisture, improves infiltration of rain or irrigation water, and
unlocks existing nutrients in the soil. With this practice, nutrients are more readily absorbed into the soil and less run-off takes place.
Any addition to the soil which improves its physical or chemical condition is considered a soil amendment. Many types of amendments are available to the gardener.
Additives to Change pH and Nutrient Levels:
An alternative to standard procedures is minimum-till gardening, also known as conservation tillage. This method is ideal for transplants to the vegetable garden.
The correct soil pH is essential for optimum plant growth. Lime and sulfur are common additives used to balance soil pH. Dolomitic limestone adds calcium and magnesium as it increases pH, making the soil more alkaline. Elemental sulfur will acidify soil. The amount of additive to add depends on the current and desired pH - one good reason to have garden soil checked periodically.
Other additives are added specifically to improve soil nutrient levels. Greensand and granite meal are sources of potassium. Granite meal is finely ground granite rock which releases its potassium slowly. Greensand is relatively low in potassium, which is readily dissolved. Other nutritional additives that can be purchased for garden use include cottonseed meal, kelp meal, leather meal, and worm castings, as well as an array of synthetic fertilizers.
Additives to Improve Soil Qualities:
The regular addition of manures, compost, cover crops, and other organic matter can raise the soil nutrient and structure level to a point at which the addition of synthetic fertilizers is greatly reduced, and in some cases, no longer needed. This highly desirable soil quality does not come about with a single or even several additions of organic material, but rather requires a serious, long-term program.
Animal manures are commonly used as a garden soil amendment. Fresh horse, sheep, rabbit, and poultry manures are quite high in nitrogen and may burn plants if applied directly to a growing garden. They are best applied in the fall and tilled under.
The use of compost is one way to get around tying up nitrogen during decomposition. Compost is usually made by the gardener from plant wastes. Correct composting can result in a valuable nutrient and humus source for any garden. The basis of the process is the microbial decomposition of mixed, raw, organic materials into humus - a dark, fluffy product resembling rich soil - which is then spread and incorporated into the garden soil. Contact your local nursery for information about building a compost pile.
Remember, your soil is alive and constantly changing. By keeping it fertile and rich, many gardening problems may be diminished. Soil is the base for plant growth, and much attention should be paid to getting and keeping it in the best condition.