Why are urea and ammonium sulfate not allowed in organic crop production?
D.W. South Dakota Answer: Urea and ammonium sulfate are prohibited fertilizers in organic production because both are synthetic or artificial commercial fertilizers. As stated in NCAT’s Organic Crops Workbook, on page 15:
Organic agriculture is built around the notion that providing nutritious food and feed is the best way to improve and sustain the health of people and livestock, and that the best way to grow nutritious food is by emulating nature, which begins with feeding the organisms of the soil. Soil micro- and macro-organisms are the external digestive system that processes organic matter, delivering a smorgasbord of minerals, vitamins, and other nutrients to the crop at a metered pace. This is in contrast to the conventional approach where crops are flooded with a limited number of soluble fertilizer nutrients, leading to “luxury consumption,” imbalanced plant nutrition, and a susceptibility to disease and attack by insect pests. The food that soil organisms need to do their job comes in the form of organic matter, thus composting, manuring, extended crop rotations that include sod crops, green manuring, and similar activities are the standard practices of organic farming. For the producers of field-scale annual crops, a cropping sequence that includes sod-forming crops is of great value. Sod-forming crops are typically perennial and biennial forage grasses and legumes. Legumes play a special role due to their ability to fix nitrogen?. Additionally, cover crops of annual grasses, small grains, legumes, and other useful plants like buckwheat are inserted into the cropping sequence wherever possible to serve as green manures.
ResourcesATTRA publication:Sustainable Soil ManagementBaker, Brian. 2004. Materials used in organic farming. Organic Farming Compliance Handbook. 2 p.www.sarep.ucdavis.edu/organic/complianceguide/materials1.pdf (PDF 103 kb)Gaskell, Mark, et al. 2000. Soil fertility management for organic crops. University of California ? Small Farm Program, Davis. 5 p.http://anrcatalog.ucdavis.edu/pdf/7249.pdf (PDF 123 kb)Mitchell, Jeff, et al. 2000. Soil management and soil quality for organic crops. University of California ? Small Farm Program, Davis. 5 p.http://anrcatalog.ucdavis.edu/pdf/7248.pdf (PDF 112 kb)