The issue of nitrogen overload and its role in global pollution problems has caused many home gardeners to seek nonsynthetic fertilizers and soil amendments to improve plant growth. There are many ways to improve vegetable and flower growing without using products that damage the environment. The Organic Materials Review Institute provides guidelines to determine the organic content of fertilizers and soil amendments.
The term fertilizer, according to Colorado State University Extension, refers to “a soil amendment that guarantees the minimum percentages of nutrients (at least the minimum percentages of nitrogen, phosphate and potash).” Organic fertilizer derives amendments from natural sources. Soil amendment is anything mixed into the soil, both general-use fertilizers and single-ingredient amendments.
USDA Organic Program
The USDA National Organic Program (NOP) allows for the use of only certain substances in fertilizer and soil amendments. The content of fertilizers is regulated by each state, but the Organic Materials Review Institute provides a list of materials that meet USDA (NOP) standards. They also provide a list of manufactured fertilizer and amendments products that meet these standards.
Synthetic fertilizers contain chemically produced nitrogen, phosphorus and potassium to boost plant growth. Organic fertilizers contain a wide range of plant and animal byproducts, compost, rock powders and various kinds of seaweed. Plant byproducts may include cottonseed, alfalfa and soybean meal. Animal byproducts, such as bat guano, feather meal, blood and bone meal, fish emulsion and fish meal, are in organic fertilizers. Seaweed products include solid and liquid forms of kelp.
General-use synthetic fertilizers are applied at the beginning of the growing season and at regularly scheduled intervals. Organic fertilizers support the growth of microorganisms in the soil, which reproduce and create a cycle of nutrients for growing plants. Organic fertilizers and amendments feed the soil. Synthetic fertilizers give plants a direct growth burst but do not contribute to soil’s continuing productivity and health.
Soil may be deficient in particular nutrients and benefit from the addition of single-ingredient soil amendments. Blood meal and bat guano are high in nitrogen. Kelp meal is a good source of potassium and minerals that support soil health. Fish bone meal can be used when soil is deficient in phosphorus and calcium. Soil testing kits are available from garden centers .