Oregon State University

natural fertilizers

until the early 20th century all fertilizers were effectively natural. Potassium and phosphorus are mined from mineral deposits called potash and rock phosphorus, respectively. Nitrogen comes from mostly animal-associated materials (manures and guano, blood meal, bone meal, fish meal, feathers, etc). For most crops, manure must be composted before being applied as a fertilizer to prevent the spread of human pathogens (like E. coli or salmonella). Approximately 5% of all US crops are fertilized with manure and manure-related materials like compost. See also nitrogen fertilizer.

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