Organic Vegetable Growing
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Growing Organic Vegetables In Iowa Introduction Many growers have already raised crops “organically” at Organic production and consumption has increased in the one time or another—simply by growing plants without last 20 years, with $20 billion in sales in 2008. More than the use of synthetic fertilizers or pesticides. Before the 4.1 million acres are in organic production in the U.S. as invention of synthetic agricultural chemicals around World the industry continues at 17 percent annual growth rate. War II, all crops relied on inherent soil fertility, augmented Consumers purchase organic foods for several reasons, by manure, kitchen scraps, or nitrogen-fixing leguminous including reduced pesticide residues (organic prohibits the crops, such as alfalfa. Sir Albert Howard (1873-1947) was use of synthetic pesticides) and perceived benefits from a pioneer in organic farming techniques that were based organic fertilization in terms of nutritional content. Many on an integration of soil life, plants, animals, and people. chefs throughout the world select organic foods for their He championed the use of crop rotations (alternating crops menus because of the perceived superior taste. In addition, every year within a given section of land) and compost organic consumers strive to support local farmers who rely applications to provide organic matter and replace nitro- on environmentally-friendly methods of production that gen and minerals lost through cropping practices. Others, help protect groundwater. including J.I. and Robert Rodale, continued Howard’s work in promoting organic methods. Certified Organic Designation Organic farming is based on the ecological principles of “Organic” is a term defined by law (Organic Food Produc- nutrient cycling, biotic regulation of pests, and biodiversity. tion Act, 1990; U.S. Department of Agriculture-National Inputs used in organic farming are derived from renewable Organic Program, 2004). As of October 2002, anyone sell- resources in order to preserve our limited supply of non- ing products labeled as “organic” must be inspected by a renewable petroleum, which is the basis for most chemi- third party to ensure compliance with federal USDA rules cals used in conventional agriculture. Organic growers rely (see Fundamentals of Organic Agriculture, PM 1880). on materials produced through sunlight, such as plants/ plant parts, and manures produced through an animal’s To sell a product as “organic,” the crop must have been consumption of plants. Recycling of wastes that are poten- raised on land where synthetic chemicals (any synthetic tial pollutants, such as animal manure, is a critical compo- fertilizers, herbicides, insecticides or fungicides) have not nent of organic farming. been applied for at least three years prior to harvest. In ad- dition, no genetically-modified organisms (GMOs) or GMO For commercial organic producers, a third-party certifier crops are allowed in organic production (e.g., Roundup- inspects annually to assure that no synthetic materials Ready® soybeans and Bt-sweet corn®). Other practices have been used in production. This “audit trail” is verified specifically disallowed for organic production include use through farm records, a system that many farmers already of “biosolids” (sewage sludge) due to concerns with bacte- embrace, by tracking planting dates, farm sections (crop rial and heavy metal contamination. Irradiated products rotations), and input application rates. Thus, the transi- also are prohibited. Organic producers who gross less than tion from organic farming to certified organic production $5,000 per year and wish to sell their produce as “organic” should be relatively easy for anyone wishing to market are exempt from certification fees but must follow organic crops as “organic.” standards and register with the Iowa Department of Agri- culture and Land Stewardship (see References). Soil Health and Nutrient Cycling All organic systems are based on the principle of nutri- ent cycling. Nutrients in the farm system are in a constant state of cycling. As plants and animals are raised together, their residues are recycled into the soil as fertilizers for the next crop, which may then be used to feed animals and plants in the system. Because livestock are considered part of the organic farm system, many organic producers raise chickens, rabbits, and other small livestock in fenced areas or in movable, pasture-based chicken tractors. Iowa is an ideal location for livestock operations; growers without livestock should be able to locate manure from nearby farms or livestock operations. Organic vegetable crops can be planted using mechanical transplanters to aid efficiency. 2 Making or purchasing compost for your soil fertility By testing your soil, you can estimate of the needs will include assuring that all ingredients meet quantity of nitrogen your cover crop provices organic standards (see table 1). (shown: hairy vetch and rye). Raw manure can be used from animals that have A crop rotation plan is helpful in protecting against pest not been raised organically but all manure must be problems and maintaining soil health. Horticultural crops incorporated in the soil 4 months before harvest or should be rotated with a leguminous cover crop at least composted (see Composting section on page 4). Compost- once every five years. No more than four out of six years ing at the proper oxygen level, temperature, and humidity should be in row crops, and the same row crop cannot be should break down all synthetic materials in manure, but grown in consecutive years on the same land. Legumes if you are concerned about the persistence of antibiotics, (alfalfa, red clover, berseem clover, hairy vetch) alone, or hormones, or other synthetic substances fed to animals in combination with small grains (rye, wheat, oats, barley), that have not been raised on organic farms, you may wish should be rotated with row crops (corn, soybeans, ama- to use manure only from organic farms or from a certified ranth, vegetables) to ensure a healthy system. organic supplier. An example of a seven-year rotation in Iowa would be a (1) Always ask for a list of ingredients in purchased manure hairy vetch/rye cover crop, (2) tomatoes, (3) onions, (4) sal- or compost. If prohibited, synthetic substances have been ad greens, (5) garlic, (6) Austrian winter pea/triticale cover used in processing or pelletizing the product, you may not crop, (7) strawberries. The highest nitrogen-demanding wish to use the product on your farm. crops are followed by crops with lower demands, followed by nitrogen-supplying crops of legumes and small grains. Non-manure-based composts also are available, but are Plants of the Solonaceae family (tomatoes, potatoes, generally lower in nitrogen (N) than manure-based com- eggplant, pepper) should be separated by a minimum of post because they use mostly plant-based ingredients, three years to avoid nematode or disease problems from such as wood chips or straw (see table 1). previous Solonaceae crops. Beneficial microorganisms also are critical for recycling nutrients, and are supplied through manure, compost, and cover crops. Compost application rates range from 100 to 150 pounds of nitrogen per acre, depending on crop needs, existing soil fertility, and nitrogen from other sources (cover crops). Because most composts in Iowa range from 1 to 3 percent nitrogen, rates of 6,000 to 12,000 pounds of compost per acre are commonly applied. Soil Quality and Crop Rotations Soil quality includes all the physical, biological, and chemi- cal (as in mineral elements, such as nitrogen) components necessary for soil health. Only naturally-occurring materi- als are allowed in organic production and processing and Hairy vetch should be plowed down or rolled when all applied materials must be recorded in farm records if 10 to 20 percent of plants are blooming. any produce is sold as “organic.” 3 temperature of 140°F for at least three days during the Table 1. Composition of typical feedstocks in compost operations. composting process to adequately decompose organic ma- Material N P2O5 K2O C/N terials and kill plant pathogens and weed seeds. Dairy manure 0.6-2.1 0.7-1.1 2.4-3.6 18 Horse manure 1.7-3.0 0.7-1.2 1.2-2.2 30 Adequate moisture and temperature are required for Poultry manure 2.0-4.5 4.5-6.0 1.2-2.4 6-16 proper composting (strive for 45 to 50 percent moisture). Sheep manure 3.0-4.0 1.2-1.6 3.0-4.0 16 If compost piles reach ideal temperatures and moisture Swine manure 3.0-4.0 0.4-0.6 0.5-1.0 14 conditions, and are routinely turned when temperatures reach 140°F, a finished compost (with the look and smell of Fish meal 10.0 6.0 - 3.6 soil) can be obtained in 6 to 8 weeks. Alfalfa hay 2.45 0.50 2.10 16 Wheat straw 0.50 0.15 0.60 127 Other composting systems include vermicomposting Apple fruit 0.05 0.02 0.10 401 (using earthworms in “beds” or “towers” to decompose 2 Apple leaves 1.00 0.15 0.35 54 manure and other wastes), in-vessel digesters, and Banana peels 0 3.25 41.76 anaerobic systems. Beans (pods) 0.25 0.08 0.30 Coffee grounds 2.08 0.32 0.28 20 Eggshells 1.19 0.38 0.14 Other Soil Amendments and Foliar Treatments Soil testing is essential to determine which, if any, amend- Fish scrapes 6.50 3.75 - ments are needed and in what amounts. Iowa State Uni- Potato peels 0 5.18 27.50 193 versity and private labs in the Midwest can analyze your Wood ashes 0 1.50 7.00 soils. Sawdust 0.24 440 1 Includes all fruit wastes (average) Although compost contains the majority of necessary nu- 2 Includes all leaf wastes (average) 3 Includes all vegetable wastes (average) trients, many other soil amendments are available to add nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), Composting sulfur (S), and other nutrients to soil and plants.