Gardening Articles: Care :: Soil, Water, & Fertilizer

Organic Fertilizers

by Lee Reich


Sooner or later, every gardener discovers that for good results -- whether in the vegetable garden, perennial border, or lawn -- replenishing soil nutrients is necessary. And one of the key choices is whether to use organic or synthetic fertilizers. Synthetic fertilizers are manufactured. Organic fertilizers are derived from plants and animals, and from naturally occurring mineral fertilizers.

Why Use Organic Fertilizers?

One advantage of organic fertilizers is that their nutrients are doled out as a steady diet in sync with plant needs. Because the nutrients come from natural sources, a portion of them may be temporarily unavailable to plants until released by a combination of warmth and moisture -- the same conditions plants need to grow. Released slowly, the nutrients from organic fertilizers are unlikely to burn plant roots or be leached away by water. And a single application may last a whole growing season.

You also might choose organic fertilizers for philosophical or environmental reasons. Organic fertilizers generally place fewer demands on energy resources, and they offer opportunities to recycle "garbage".

The more concentrated a fertilizer (even an organic one), the less organic matter it contains. Fertilizers containing high concentrations of nitrogen, when used alone, can actually deplete soil organic matter, so if you use any such fertilizer, apply plenty of bulky organic matter, too. Dig materials such as straw, peat, compost, and leaves into the soil, or lay them on as mulch.

Naturally occurring mineral fertilizers are organic in the "not-synthetic" sense, but because they don't contain organic matter, they're not included in this list. Among them are Chilean nitrate, rock phosphate, greensand, and sulfate of potash magnesia.

Synthetic fertilizers do have some advantages. They cost less, are easier to transport, and are more uniform in nutrient content. All but controlled-release synthetic fertilizers are more quickly available to plants than organic fertilizers.

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