How to make your own organic fertilizer

Organic components

Seed meals and various kinds of lime are the most important ingredients. These alone will grow a great garden. Seed meals are byproducts of making vegetable oil. They are made from soybeans, flaxseed, sunflowers, cotton seeds, canola and other plants. Different regions of the country have different kinds more readily available. Seed meals are stable and will store for years if kept dry and protected from pests in a metal container with a tight lid.

Lime is ground, natural rock containing large amounts of calcium, and there are three types. Agricultural lime is relatively pure calcium carbonate. Gypsum is calcium sulfate and is included because sulfur is a vital plant nutrient. Dolomite, or dolomitic lime, contains both calcium and magnesium carbonates, usually in more or less equal amounts. If you have to choose one kind, it probably should be dolomite, but you'll get a better result using all three types. These substances are not expensive if bought in large sacks from agricultural suppliers. (Do not use quicklime, burnt lime, hydrated lime or other chemically active "hot" limes.)

If you routinely garden with this homemade fertilizer mix, you won't need to apply additional lime to your garden. The mix is formulated so that it automatically distributes about 50 pounds of lime per 1,000 square feet each year.

Bone meal, phosphate rock or guano (bat or bird manure) all boost the phosphorus level, and phosphate and guano usually are also rich in trace elements. Bone meal is usually available at garden centers. Kelp meal (dried seaweed) has become expensive, but it supplies some things nothing else does -- a complete range of trace minerals plus growth regulators and natural hormones that act like plant vitamins, increasing resistance to stresses.

Guano, rock phosphate and kelp meal may seem costly or difficult to obtain, but they add considerable fortitude to the plants and increase the nutritional content of your vegetables.

Some rock dusts contain a complete range of minor plant nutrients and may be substituted for kelp meal.

Making the organic fertilizer

To concoct the fertilizer mix, measure out all materials by volume: that is, by the scoop, bucketful, jarful, etc. Proportions that vary by 10 percent either way will be close enough, but do not attempt to make this formula by weight. An old 5-gallon plastic bucket will allow you to stir up about 14 quarts.

Mix uniformly, in parts by volume:

4 parts seed meal

1/4 part ordinary agricultural lime, best finely ground

1/4 part gypsum (or double the agricultural lime)

1/2 part dolomitic lime

Plus, for best results:

1 part bone meal, rock phosphate or high-phosphate guano

1/2 to 1 part kelp meal (or 1 part basalt dust)

This recipe is inexpensive when judged by its results. Farm feed and grain dealers are the best sources for large bags of seed meals, which are typically used to feed livestock. The other ingredients usually can be found at garden shops, although they probably will be sold in smaller quantities at higher prices per pound. You may find the best prices by mail order or on the Internet.

Applying the fertilizer mix

Once a year, before planting, uniformly spread this mix and finished compost over your growing area. For light feeders, such as carrots, radishes or onions, apply 4 quarts of fertilizer, plus about a quarter inch of compost, per 100 square feet. For heavy feeders, such as corn, potatoes, squash or tomatoes, apply six quarts and a half-inch of compost over the same areas. If you're planting in hills, mix an additional cup of fertilizer into each. Gardeners dealing with heavy clay soils should apply more compost and about 50 percent more fertilizer.

During the growing season, sprinkle small amounts of fertilizer around medium- and high-demand vegetables every three to four weeks, thinly covering the area that the roots will grow into. As a rough guide, side-dress about 4 to 6 additional quarts total per 100 square feet of bed during a crop cycle.