Nutrient Content of Fertilizer and Organic Materials
Table of Contents
Proper soil and crop management are required when using fertilizer materials to avoid contaminating surface water or groundwater. Plant nutrient requirements can be met by applying inorganic or organic fertilizers. Inorganic materials may be used separately or blended to form multinutrient fertilizers; some organic sources are also blended and sold under various commercial labels. The quantity of nutrients sold in commercially available inorganic and organic fertilizer materials are guaranteed by the manufacturers and are listed on each bag of fertilizer material sold in North Carolina.
This publication serves as a reference for most commercial grade fertilizer
materials. Elemental quantities listed in
Nutrients listed for organic materials in
the following tables are averages and may not accurately reflect the quantity
in a specific source. Using these values can result in either overfertilization
or underfertilization in many cases. To determine the quantity of nutrients
in a specific organic source, send a sample to a qualified laboratory.
The North Carolina Department of Agriculture, Agronomic Division, performs
analyses for a reasonable fee. Contact the Plant and Waste Laboratory,
Remember that most of the nutrients reported are not readily available for plant growth. Nutrients in organic matter must be released by soil microorganisms through a decaying process called mineralization. This biological process is affected by variations in moisture, temperature, and the microbial species and populations present in the soil. Therefore, organic materials are far less predictable in nutrient content, nutrient release, and nutrient-use efficiency than commercial grade fertilizers. Because of this unpredictability, organic materials are frequently overapplied, which may lead to contamination of surface water or groundwater by excess nutrients such as nitrate. Organic materials can serve as effective and environmentally sound fertilizer materials only if their nutrient contents are known and their mineralization rates are estimated closely. The report received on samples sent to the NCDA Agronomic Division lists the nutrient contents and estimated rates of mineralization.