Unfortunately, not all organic gardeners have access to manure or the room for a compost pile or tumbler. Perhaps your garden is just a few window boxes on a balcony. It could be that backyard space is precious, and there is only room for a couple of half barrels and a small growing bed between the sidewalk and the front porch; but you can still treat properly what soil you have by using purchased organic fertilizers and soil builders instead of synthetics. You may even be able to buy fully prepared compost from the county or town in which you live, as many local governments now sponsor composting projects at local landfills.
With the growing interest in organic gardening, though, many companies have brought what they call “organic” or “natural” fertilizers to market, and your are likely to find one or more of them available at your local hardware store or garden center. Just be sure to read the label of what you buy, since the dream of profits has led more than one businessperson down the road to subtle deception. A few products are little more than standard synthetic fertilizers with a bit of some organic material such as fishmeal added (and then blazoned in large type of the bag). These kinds of products will not build the soil.
Here’s what to look for when you buy organic fertilizer. First, check the NPK listing; if any of the numbers is above eight, look for a list of ingredients; most organic materials are lower than that in immediately available nutrients, which is what the number must legally mean. Remember, that is the advantage of organic materials: that their nutrients are not immediately available, but rather are released slowly, over time, at a rate the plants can use without waste.
Second, scan the list of ingredients for words like ammonium, muriate, urea, nitrate, phosphoric, or superphosphate; if these words or their variants are part of the ingredients, don’t buy. The words phosphate and sulfate themselves are not necessarily indicators of processed or synthesized materials; but if combined with any of the key words above, they are. Other ingredients to watch out for are cottonseed meal and leather tankage, not because they aren’t organic, but because they are frequently contaminated with harmful residues. The same points apply to liquid fertilizers.
When using commercial organic fertilizers, follow the instructions and the recommended application rates listed on the package. Don’t double up because the listed NPK is lower than what you might be used to using. And be careful to keep track of your soil’s organic matter level; these purchased fertilizers, unless they are made from composted manures (many are), do not add organic matter to the soil—and organic matter is at the heart of organic gardening.