Standard chemical fertilizer is the norm in worldwide agriculture, but the use of organic materials and methods is gaining in popularity. Gardeners often choose standard fertilizer because it is well-known and familiar. Some gardeners choose organic fertilizers because they want to eliminate toxic chemicals from their environment for nutritional or health safety reasons. A comparison between the two methods can be helpful in making a choice.
Organic farming and the use of organic fertilizers is the oldest form of agriculture. Standard, or chemical, fertilizers were developed commercially after World War II. The discovery of the process of turning air into liquid ammonia was the catalyst for creating nitrogen-based fertilizers. Organic fertilizer products have grown in popularity as organic farming has increased. In 2008 there were 4.8 million acres of U.S. land under organic production. As of 2008, California leads the nation in certified organic cropland.
Organic Fertilizer Content
Commercial organic fertilizers are derived from natural sources such as animal manure, cottonseed meal, feathermeal, bone meal, alfalfa, seaweed extracts, fish waste products and mined rock powders. Some fertilizers sold as organic may contain sewage sludge, which is not a USDA National Organic Program approved material. The Organic Materials Review Institute provides lists of companies and products that adhere to national organic standards (see Resources).
Standard Fertilizer Content
Nitrogen is the nutrient most needed by growing plants. It is identified first on the N-P-K label on standard fertilizer. Phosphorus(P)and potassium (K) are needed in the next highest amounts. Many chemical fertilizers also provide trace minerals, which are listed next in the labeling. Chemical nutrients are absorbed directly by growing plant root systems, providing an immediate boost to growth.
Standard fertilizer does not provide nutrition for soil. Living organisms in the soil food web need organic materials to survive. Micro-organisms in soil transform organic materials into the plant nutrients necessary for human health. The International Fertilizer Association recommends that farmers add organic matter to maintain soil fertility because "the activities of soil organisms are indispensable for high soil fertility and good crop production." Organic fertilizer feeds nutrients to soil, which plants absorb.
Chemical nitrogen in standard fertilizer has been identified by the World Resources Institute as a primary cause of global pollution. Excessive nitrogen in air and water distorts plant and animal natural life cycles, producing abnormalities and health problems. Organic fertilizer provides adequate nitrogen for plant growth without unbalancing ecosystems. Nitrogen in organic fertilizer is created by the living organisms that populate the soil food web.