Most questions have to do with trying to understand what the differences are, usually with an underlying question, "Why should I use organic fertilizer?". The other uncertainty has to do with "What is an organic fertilizer?".
Since most people relate to fertilizing products by brand name, not ingredients, the second question is easier to answer than the first. Brands like Miracle-Gro, Scott’s, Vigoro, Best, Osmocote and Shultz are synthetic, not organic, although each of these companies is attempting to enter the growing organic fertilizer marketplace. The most popular organic fertilizer brands are likely Dr. Earth, E.B. Stone, Whitney Farms and Foxfarm.
But the best way to distinguish organics from synthetics is by a review of the ingredients on the side of the box or bag. Synthetics will list sources like ammonium nitrate, monammonium phosphate, ammonium sulphate, urea, potassium chloride, etc. Organics will be from sources like bone and fish meal, rock phosphate, kelp, alfalfa and soybean, various guanos and so on.
Answering the second question of "Why should I use organic fertilizer?" takes a bit more explaining and gets a little technical. I’ll try to simplify the science as best I can.
At the most basic level, organic fertilizer simply means a fertilizer derived from organic matter, such as from the ingredients mentioned above. Chemical fertilizers are usually processed from things like petroleum, or some of the gasses that are found in places where petroleum exists.
Chemical fertilizers, when mixed with water, are in a form a plant can use immediately. Nitrogen is present in forms that quickly dissolve in water to form a nitrate ion (among other things). Phosphorus is present as phosphate, which provides the phosphate ion. Potassium is usually in the form of potash, delivering a potassium ion. Of course, there are about 14 other nutrients that are also essential to plants, but I there isn’t space here to go into all of those.
Chemical fertilizers are easily over-applied, since they are essentially all released to the plant right away. Perhaps even more important, since they are water soluble and move wherever water moves, chemical fertilizers are much more easily removed from the root zone (and by the way, end up in our groundwater, watersheds and coastal waters). Also, be reminded that chemical fertilizers generally are derived from non-renewable resources.
Chemically based fertilizers are nutrient-carrying salts that don’t contain organic matter. When used consistently and without organic components they can deplete the soil, which kills the microbes, worms, and other residents that keep the soil in optimum shape. Salts also build up in the soil, eventually interfering with the very absorption of the same nutrients you are applying.
Because synthetics release their nutrients instantly, there is a growing opinion that the nutrients are released too quickly, creating a great deal of top growth before the roots are able to catch up. This kind of growth leads to a weaker plant, needing more water, an ongoing dependence on additional fertilizer and greater vulnerability to pests and disease.
Organics are intrinsically different. They are not in a form plants can use immediately. They require the presence of soil microorganisms (various soil bacteria and fungi) to convert them to something that is "available" to the plant.
From a plants point of view, organics have several advantages: 1) It's almost impossible to over-feed your plants, since they only get the nutrients that are made available by the soil microorganisms. 2) You can't wash an entire "feeding" away. You can certainly wash away what's been broken down at any given point in time, but it won't take long for the soil life to make more. 3) Most important, you get a much more even feeding over a longer term; just how long depends to a large degree on soil temperatures and the health of your soil microorganisms. Here in Southern California I can usually apply one or two feedings to most landscape plants and that will cover the entire year.
Chemical fertilizers will not improve the structure of the soil. In fact, because they are composed of concentrations of salts, they are capable of killing off many of the soil organisms that are responsible for healthy soil structure. If only chemical nutrients are added, the soil gradually loses its organic matter and microbiotic activity. As this material is used up, the soil structure breaks down, becoming lifeless, compact and less able to hold water and nutrients. The result is pretty clear - you'll have to use more and more fertilizer to keep up.
Additional benefits of organics are that many of them are just byproducts of some already-existing process. Bone meal and blood meal are made from leftovers. Seed meals are taken from what's left after harvesting and processing. And of course, these sources are renewable.
So there it is. I've tried to show why organic fertilizers are worth considering, even if you aren't an organic gardener.
Ron Vanderhoff is the Nursery Manager at Roger’s Gardens, Corona del Mar.
Questions from Readers July 2.
When should I transplant a rose? It’s in too small of a spot.
Bonnie, Laguna Beach
Certainly the easiest time would be winter, right after you perform its annual pruning, but a rose can be transplanted almost anytime if you do it right. First, prune the rose back considerably, much like you would do during its annual January pruning. Water the plant well a day or two prior and then dig as much of the soil and root as you can. Have the new location ready and plant it immediately. Water it in slowly and thoroughly. For the next few weeks shade the plant with an umbrella, keep it moist, but not soggy and mist it on warm or dry days.