Organic Matters
Decaying leaves, plants, and animals make up the 'organic matter' content of the soil. This organic matter is broken down and manufactured into nutrients by an army of microorganisms. Soils that have a high content of organic matter usually have many desirable physical properties; they are easier to cultivate, and they absorb and hold water more readily.
Although substances that improve the organic matter of soil benefit gardening in many ways, they do not add plant food value equal to that of mineral fertilizer on a volume basis. The plant food value of manure and compost varies, but the typical manure/compost available from a garden center provides nitrogen-phosphate-potash in the ratio of 0.5%-0.5%-0.5%. A mineral fertilizer formulated for use in gardens would provide nitrogen-phosphate-potash in the ratio 5%-15%-10%.
The term 'organic gardening' describes a philosophy of horticulture in which crops are grown with only manures and composts as fertilizers. Many academic experiments across North America are monitoring the use of both organic-source and mineral fertilizers, and their effects on plant growth and on the quality of the fruit, vegetable, or grain produced. This research continues to demonstrate that the source of plant nutrition does not influence plants' ability to use those nutrients. This is similar to research findings with vitamins in humans; the human body does not distinguish between a synthetic vitamin and vitamins retrieved from food.
The nutritional quality of plants fertilized with manures or composts is also being researched to compare those crops with plants fertilized with mineral fertilizers. To date, any differences in the plants' content of essential elements or vitamins have been too small to be of nutritional significance, and have favored the mineral-fertilized plants as often as those grown with manures or composts.
In the garden
Gardeners should use all practical means to conserve and increase the organic matter content of their soils, but they should do so for specific benefits: to improve the tilth, water absorption and retention, and resistance to crusting and erosion, not in expectation of some effect on the nutritional qualities of the crop produced. Practical gardeners will mix fully composted organic matter into the soil, where possible, each spring or fall to improve soil condition. Use of a mineral-source fertilizer formulated for gardens, flowers or shrubs early in the spring and later in June will promote optimum plant health.
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