By: Kathleen Delate, Professor, ISU Organic Ag Program, Departments of Agronomy and Horticulture
Getting Into Soil & Water 2012
What is Organic Agriculture?
Organic agriculture is the oldest form of agriculture on earth. Farming without the use of petroleum-based fertilizers and pesticides was the primary option for farmers until after World War II. The war brought with it technologies useful to agriculture, including ammonium nitrate, originally used for munitions, finding a ready market as a fertilizer, and organophosphate nerve gas next utilized in insecticides. Technical advances resulted in significant benefits, while negative environmental and social consequences led many to examine organic farming techniques. Organic agriculture seeks to use technical advances that consistently yield benefits, such as improved soil fertility and conservation practices, while avoiding those leading to negative impacts on society and the environment, such as water pollution and pesticide–resistant insects and weeds. Interactions between crops, animals, insects, soil, and water are key. For example, implementation of an organic soil nutrient plan may include crop rotations, cover crops, and compost to maintain or enhance soil fertility. In lieu of prohibited synthetic pesticides, biological, cultural, and physical methods limit pest expansion. Genetically-modified organisms (GMOs), or transgenic crops, such as herbicide-resistant plants, are prohibited. As defined by the International Codex Alimentarius Commission, “Organic agriculture is a holistic production management system that avoids use of synthetic fertilizers, pesticides and genetically modified organisms, minimizes pollution of air, soil and water, and optimizes the health and productivity of interdependent communities of plants, animals and people.” The 1990 Organic Food Production Act (OFPA) and 7 CFR Section 205 codified certified organic practices in the U.S. within the USDA-National Organic Program (NOP). In 2002, U.S. organic standards went into effect, creating a uniform set of regulations aiding market growth. A 36–month transition period is required between the last conventional practice, such as the application of a non-NOP-compliant pesticide and harvest of a certified organic crop. In 2008, 4.3 million acres of land were under organic production in the U.S., with 106,000 organic acres in Iowa. In 2010, U.S. organic industry sales were $29 billion, and $55 billion worldwide. Iowa is a leader in organic agriculture in the U.S. because of the high number of organic farmers (520) and processors (32), and the nationally recognized organic research and extension program at ISU.
Effects on Soil and Water Quality
Protection and enhancement of soil organic matter is critical for maintaining soil quality in sustainable agricultural systems. Recognizing the importance of soil organisms in mineralizing nitrogen for plant use, Sir Albert Howard (1873-1947), one of the pioneers of organic agriculture, formulated “The Law of Return,” acknowledging the need to recycle organic waste materials, such as manure and leaves, on agricultural fields to replenish soil organic matter (Heckman, 2006). Because a longer crop rotation is required in organic farming, and the same crop cannot be produced in consecutive years on the same field, a typical four– to six–year organic rotation in Iowa includes a legume (alfalfa, clover, or vetch) and small grain (oat, wheat, or barley), in addition to corn and soybeans. Legumes supply nitrogen while small grains supply nutrients, particularly carbon, and aid in weed management. Research at the Long-Term Agroecological Research Experiment (LTAR) experiment in Greenfield, Iowa, has shown that organic crops are competitive with conventional crops, even during transition (Delate and Cambardella, 2004). Averaged over 13 years, yields of organic corn and soybean have been equivalent to or slightly greater than conventional crops in a corn-soybean rotation. The 12-year average for alfalfa and oats, and an 8-year average for winter wheat, also show no significant difference between organic yields and the Adair County average. Soil analyses show total nitrogen increasing by 33 percent in the organic plots, with higher concentrations of carbon, potassium, phosphorus, magnesium and calcium, suggesting organic farming fosters greater efficiency in nutrient use and has higher potential for sequestering carbon. Craig Chase, Extension Farm Management Specialist, calculated organic returns to management, and found, on average, organic systems return roughly $200 per acre more than conventional crops. While research on water quality differences between organic and conventional systems is just underway in Iowa, mechanisms for an improved capacity for greater water and soil nutrient retention in organic fields may center around enhanced soil organic matter content. Recent data from a 12–year study in Michigan (Snapp et al., 2010) showed organic fields with half the annual nitrate leaching than conventional fields. NO3-N concentrations and subsurface drainage discharge also were reduced by 50% and 41%, respectively, under extended-rotation systems in Minnesota (Oquist et al., 2007). Organic agriculture presents a unique opportunity for Iowans to take advantage of the growing market demand for organic products. More and more farmers are interested in both the profitability and the environmental benefits that organic systems can yield .
References:
Delate, K., and C.A. Cambardella. 2004. Agroecosystem performance during transition to certified organic grain production. Agronomy Journal 96:1288-1298. Heckman, J. 2006. A history of organic farming: Transitions from Sir Albert Howard’s war in the soil to the USDA National Organic Program. Renewable Agriculture and Food Systems 21:143-150. Oquist, KA., J.S. Strock, and D.J. Mulla. 2007. Influence of alternative and conventional farming practices on subsurface drainage and water quality. J. Environ. Qual. 36:1194-1204. Snapp, S.S., L.E. Gentry, and R. Harwood. 2010. Management intensity–not biodiversity–the driver of ecosystem services in a long-term row crop experiment. Agriculture, Ecosystems, and the Environment 138(3-4):242–248.
