Vegetable and fruit gardens benefit from regular applications of fertilizer. Plants deplete nutrients from the soil as they grow and these nutrients must be replaced. Natural decay processes replace nutrients in the wild but in our gardens we need to help nature with this process. Fertilizers feed nutrients directly to plants or they are released slowly through the soil. Global pollution problems have developed from overuse of chemically based fertilizers.
Fertilizer is material put on the uppermost layer of soil to enhance plant growth. Soil amendments are substances mixed into existing soil to enhance plant growth and enrich soil fertility. Fertilizer is either derived from natural sources or manufactured through chemical processes.Natural fertilizer also contains living microorganisms. Compost is a form of natural fertilizer.
Broadcast fertilizer is made in pellet or granule form for easy spreading. Foliar spray fertilizer is liquid concentrate all-purpose fertilizer made to use in sprayers. It provides nutrition directly through microscopic pores on the leaf surface. Large farms use fertilizer in drip-irrigation systems. Standard chemical fertilizer concentrates on delivering high levels of nitrogen, phosphorus and potassium.
Fertilizer provides nitrogen to plants, which is the nutrient needed in highest concentration. Chemical fertilizer nitrogen gives a growth burst directly to plants but does not enhance soil biology. The high levels of nitrogen in chemical fertilizer have been identified by the World Resources Institute as the primary cause of nitrogen-overload and global pollution problems. Nitrogen saturation disrupts soil chemistry, preventing plant root absorption of other essential minerals. This leads to a decline in soil fertility.
Plants need 17 nutrients for optimum growth, according to Utah State University horticulturist Jerry Goodspeed. Organic fertilizers derived from natural sources are often a more complete source of nutrients than chemical fertilizers. Organic fertilizer is made from sources such as cottonseed meal, seaweed products, animal manure, fish waste, feathermeal, bone meal, mined rock powders and alfalfa meal. Nutrients from natural sources support and enhance soil biology as well as provide the nutrients plants need.
Soil Food Web
Fertilizer products derived from natural sources contribute to the health of the soil food web. Dr. Elaine R. Ingham of the USDA Natural Resources Conservation Service describes the soil food web as living organisms that "make it possible to have clean water, clean air, healthy plants and moderated water flow." Living soil organisms feed on organic matter such as compost fertilizer. Nutritional content of vegetables is created by living soil organisms which exude nutrients into soil.