A common misconception is that synthetic fertilizers are better than organic. Another misunderstanding is that organic is better than synthetic. You can make political or environmental arguments for synthetic or organic fertilizer, but the plants can't tell the difference as long as the nutrients are available. However, don't forget the many benefits of adding humus to your soil, which only organic amendments can supply. Brand labels mean nothing to plants. It's the fertilizer analysis that countsthe list of three, sometimes four, numbers listed on the bag. They stand for the percentage of nitrogen (designated by the international chemical symbol N), phosphorus (P), potassium (K), and when present, sulfur (S), in the product, in that order. As mentioned in Chapter 1, these are the major elements plants need (except sulfur, which is a secondary element). Trace elements are also necessary, but manufacturers may or may not list them on labels. Organic fertilizers are much more likely to include these than manufacturers of chemical formulas.
Plants can only use nutrients that have been reduced to the molecular form. Chemical fertilizers work so fast because they have already been processed into the molecular form, whereas organic fertilizers must first be broken down by soil microbes. This activity depends on soil temperature. Below 70°F, soil microorganisms work slower, which makes the nutrients in organic fertilizer unavailable to plants in cold soils. Organic fertilizers release nutrients over a period of time, unlike synthetic fertilizers which make the nutrients available at time of application.
Chemical fertilizers dissolve fairly quickly in water, which makes them easily accessible to plants. Their labels instruct to water thoroughly after application. Unfortunately, this ready solubility also means that chemical fertilizers, unlike slow-release organics, leach more quickly from the soil.
For the best results with the least expense, strategically combine the two types of fertilizer. In the spring, while the soil is still cool, apply chemical fertilizer to lawn, flower borders, and vegetable gardens. Once the soil is warm, switch to compost or another low-cost organic source. Organic fertilizers are not necessarily more costly than synthetics. This is commonly misstated, because the measurable amount of nitrogen, phosphorus, and potassium in synthetic fertilizers costs less per pound than those in many commercially prepared organic fertilizers. But those aren't the only sources of organic fertilizer. Once you know, roughly, the fertilizer analysis of organic compounds, which varies with different sources, you can mix your own fertilizers balanced for your particular needs, at a fraction of the cost.
This is where ingenuity and the willingness to scrounge for something pays off. I never buy fertilizer, and you don't have to either. So long as you supply the plants' nutrient requirements, it just doesn't matter to them where the nutrients come from, whether it is an organic or synthetic source.
The most common mistake gardeners make is thinking more is better. If a bag of fertilizer says to apply a cup for every 10 feet of row, then two cups must make plants really grow. That is not the case. Manufacturer's instructions are not arbitrary numbers that somebody guessed at. Manufacturers base their instructions on the ability of plant roots to absorb nutrients in a set amount of time. This rate varies with the type, age, and health of the plant, as well as the soil type and texture.
Not only is it cheaper to use the original soil to backfill a planting hole, it is better for the plant. By digging a hole and filling it with amendments or foreign soil, you create an artificial environment with a dramatic interface between it and the surrounding native soil. The result is water does not flow freely between the two media, and plant roots become entrapped in the planting hole, much like they would in a container. At first, the plant will look normal, in fact, most plants will appear to thrive. After a while, the plant becomes virtually potbound and dies, leaving the conscientious backfiller to wonder why.
