More and more gardeners are interested in growing organically. This is especially true for gardeners growing fruits, vegetables and even grains. Reasons include concern over pesticide use, human health, preservation of beneficial insects and microbes and reducing input costs.
Part of growing organically is eliminating pesticide use or using organic pesticides derived from natural materials such as minerals, fungi, plant extracts and more. The other side of the organic equation, though, is how to fertilize and amend the soil with organic inputs.
First off, let’s get one thing straight: Growing organically does not mean that you never, ever fertilize or prevent or treat insects. That is a production method I like to call “organic by neglect.”
Unfortunately, I see it all too often — gardens suffering for lack of nutrients or overrun with pests. If anything, growing organically means that the gardener needs to pay closer attention to meeting plant needs and make a more concerted and comprehensive effort at maintaining the garden.
It takes a little more planning and thought when you can’t rely on high-powered pesticides and fertilizers to do all of the work for you.
What is organic fertilizer?
Organic fertilizers and soil amendments are derived from a number of different sources. To be “organic,” a fertilizer must be derived from a natural source, such as an animal or plant byproduct, rock dust (minerals) or seaweed that meets a minimum standard of fertility.
Plants require a variety of different nutrients to function at their fullest. The “big three” nutrients that you commonly apply in the form of fertilizer are nitrogen (N), phosphorous (P) and potassium (K). Plants also demand calcium (Ca), magnesium (Mg) and sulfur (S) in higher amounts. Correction for sulfur is generally not required in West Virginia, as our soils contain enough for efficient plant growth. Calcium and magnesium are typically added through the use of lime, which is a rock dust and considered organic.
Plants also require, in trace amounts, a short list of micronutrients. You’ve likely not thought of some of these nutrients since you were forced to memorize the periodic table in school. These essential nutrients are boron, chlorine, copper, iron, manganese, molybdenum and zinc. These trace nutrients are added when you fertilize with a plant-based organic fertilizer or use compost as a soil amendment.
Speaking of compost, while it is a great soil amendment to improve soil texture, support beneficial microbes and critters, and provide trace nutrients, it really isn’t a big source of the N-P-K that you find in a “fertilizer.” It is considered more of a soil amendment than a fertilizer. For example, the nitrogen level in compost is so low that it would take a few hundred pounds per 1,000 square feet of garden space to supply the required nitrogen. And that application would need to be made every year.
Selecting an organic fertilizer
There are several options available when it comes to organic fertilizers. Several companies have started producing bagged fertilizer products that are made with a combination of organic substances.
These fertilizers offer a balanced nutrient profile and often contain micronutrients and even beneficial bacteria and fungi. Some brands that come to mind are Epsoma Garden-Tone and Osmocote.
These fertilizers, and organic fertilizers in general, are lower in nutrients than their conventional counterparts. For example, Epsoma Garden-Tone is a 3-4-4 fertilizer.
I would suggest using these fertilizers as a side dressing in the immediate plant area rather than a fertilizer broadcast over the whole garden — it would take way too much to do that, especially if the garden is large.
You can also tailor your fertilizer application by adding individual components and products to meet your plant nutrient needs (based upon your soil test results, of course — Kanawha.ext.wvu.edu/agriculture/soiltest). For example, alfalfa meal or pellets such as what you buy for animal feed have a fertilizer rating of 2-1-2 and provide micronutrients. Corn gluten meal is high nitrogen (9-0-0), as are cottonseed meal (6-0.4-1.5) and soybean meal (7-2-1).
On the animal-byproduct side of the spectrum, blood meal (12-0-0), bone meal (3-15-0) and fish emulsion (5-2-2) are commonly available and widely used organic fertilizers. These materials are byproducts of the meat-processing industry.
Composted manures can also be used to add nutrients to the garden. Most manures have 1 percent or less of each nutrient.
Poultry manures such as chicken and turkey are the highest. For example, composted chicken litter is rated at around 3-2-2. When adding composted manures, it is necessary to wait at least three months before harvesting to avoid possible contamination with E. coli.
The waiting period should be even longer if the crop comes into contact with the soil (root crops or leafy greens) or if fresh manure is used.
Phosphorous and potassium are available in several mineral forms as well. Rock phosphate (0-3-0) can be used for phosphorous, though it generally breaks down very slowly in the garden. Both muriate of potash (0-0-60), or potassium chloride and potassium sulfate (0-0-50) can add potassium to the garden.
Unlike conventional fertilizers, organic fertilizers often need time to incorporate into the soil. Plant and animal byproduct fertilizers need to be decomposed by microbes in the soil to a form usable by the plant.
Likewise, mineral fertilizers also need to break down in the soil. Organic fertilizers need to be added at least four months before the garden is planted, so fall is the time to incorporate these fertilizers.