What Makes Gardening Organic?

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It is fairly common to hear people claim to be organic gardeners, and in the next sentence describe applying Sevin dust or 10-10-10 fertilizer to their garden. This reminds me that it is not always clear what organic gardening is. Some have their own definition of it, whether they have studied organic standards or not. If you strive to garden organically it is important to understand what that really means, and if you are a consumer seeking organic foods, it is helpful for you to know how to differentiate in the shopping aisle.

To be called “organic”, a farm product must be grown under standards regulated by the US Department of Agriculture (USDA) National Organic Program (NOP). The program sets standards which dictate what inputs, including seed, fertilizers, pesticides, and other materials can be used in Certified Organic production. This program was founded in the early 1990s as a way to distinguish farms striving to eliminate the most toxic pesticides, reduce off-farm inputs, and reduce environmental impact. It should be noted that many farms aim for these goals, whether or not they participate in the NOP.

Certified Organic farms undergo annual audits by third-party certifiers which may enforce additional standards, in addition to NOP standards. They will usually display the USDA Certified Organic symbol in their marketing. It is illegal for a farm to use the word organic in their advertising material if they are not certified through this program, unless they sell less than $5000 per year. No agency will police your home gardening practices. But if you are claiming to give away or sell small amounts of produce, only call it “organic” if you are, at least, avoiding the prohibited substances. So, how do you know what materials are permitted? The Organic Materials Review Institute (OMRI) approves products for use in organic farming and gardening. Approved products carry an “OMRI-approved” symbol on their label. On seed or plants, look for the USDA Certified Organic label.

Only fertilizers derived from natural sources, such as manure, compost, waste products, and some mined materials such as limestone, can be used in organic farming and gardening. Synthetic fertilizers such as a 10-10-10, 18-46-0, 34-0-0, and 21-0-0, are not allowed. These supply high levels of plant-available nutrients, especially nitrogen, but they are more susceptible to loss to the environment through leaching or volatilization. Their production is also energy-intensive. Organic fertilizers tend to have lower nutrient analyses, meaning you need more to supply the same number of pounds of nutrient. But they usually supply organic matter in addition to fertilizer value, which in the long run can facilitate nutrient capture and storage in the soil.

Most organic fertilizers must undergo microbial processing before plant-available forms are released. The nutrients are often best captured and most available to plants if the fertilizers are incorporated into the soil, rather than applied to the surface. Examples of organic fertilizers include composted manure products, blood meal, bone meal, plant-based products such as alfalfa meal, greensand, Tennessee rock phosphate, fish emulsion, and other plant-based liquid fertilizers. While these are natural products, a Certified Organic farm could only use these products if produced in accordance with Organic program standards.

Organic farms must develop management plans that incorporate practices such as cover cropping that promote build soil organic matter and health. Organic matter improves soil structure, promotes healthy water movement, hosts beneficial microbial activity, and facilitates nutrient cycling in the soil. Many non-organic farms incorporate similar practices to enhance productivity and health of their crops, soils, and ecosystems. These are good practices for any gardener, as well. Consider regular additions of compost or manure, growing cover crops when no other crops are growing, mulching with straw that is turned into the soil at the end of the season, and turning in crop residues.

Organic gardening does allow for use of approved pesticides. Like fertilizers, they are derived from natural sources. They are usually less persistent in the environment and less toxic, or have a lower potential for off-target impact. Examples of common insecticides approved for organic use include spinosad, pyrethrin, Bacillus thuringensis, neem oil, azadirachtin, kaolin clay, insecticidal soap, and some horticultural oils. Sevin, malathion, bifenthrin, and imidacloprid are not for use in organic gardening.

Most fungicides, organic and not, have a preventive, rather than curative effect. Preventive organic fungicides include Bacillus subtilis, Bacillus amyloquofaciens, sulfur, and others. Copper fungicides are preventive, but generally, only fixed copper products with the active ingredient copper octanoate or copper soap are acceptable for organic gardening. Other copper fungicide formulations move more easily into the environment or contain surfactants not suitable for organic use. Potassium bicarbonate and oxidate are organic-approved fungicides that can kill fungal pathogens when present. Cholorothalonil, thiophanate-methyl, captan, and mancozeb are not for use in organic gardening.

Organic farms must use non-pesticide methods of pest control before a pesticide can be applied, and gardeners should do the same. It is important to properly identify and understand pests, and use cultural and preventive practices to prevent them when possible. Examples include crop rotation, using row cover or insect barriers, proper plant spacing, mulching, trellising, using resistant varieties, using drip irrigation or soaker hoses, turning in crop residues, and providing habitat for beneficial insects. For insects that are not well-controlled with organic products, such as squash bug, hand-picking adults, and identifying and destroying eggs can keep populations low. Slow the spread of disease by removing infected leaves when you see them.

There are a limited number of organic herbicides available for weed control. Most contain vinegar or acid-based active ingredients. These are not systemic, so they only kill plant tissue that they contact, and their use is limited. Corn gluten meal is also used to prevent weeds in lawns. Because there are few effective herbicides for organic gardeners, weed control is typically performed by hoeing, hand-weeding, tilling, plastic, or mulches.

While many organic inputs in theory have a reduced environmental impact, this is only true when they are used properly. All gardeners should use appropriate rates and application methods of any input to minimize impact and costs. Apply fertilizer according soil test or crop-specific recommendations. Follow pesticide label recommendations related to application timing, safety concerns to pollinators, weather events, personal protective equipment, and pre-harvest interval. Before using any pesticide, be sure to properly identify your pest to ensure that you choose the right tool to control it. If you have questions about what organic products can be substituted in your garden, contact the N.C. Cooperative Extension, Wilkes County Center, Monday–Friday, 8:30 a.m.–5 p.m. at 336- 651-7335.