Organic Byproducts as Fertilizers: Land Application and Permit Exemption - PUB3049

Organic Byproducts and Fertilizers

Fertilizers are regularly used on agricultural fields to promote growth and crop production. Fertilizers add vital nutrients to the soil, including nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, boron, chlorine, cobalt, copper, iron, manganese, molybdenum, sodium, and zinc. The Missouri Fertilizer Control Board (MoFCB) administers and enforces Sections 266.291 – 266.351, RSMo, which includes permitting requirements for fertilizers.

Organic byproducts from wastewater treatment or food production may have agronomic value as fertilizers and soil amendments when used correctly. The Department of Natural Resources (Department) allows organic byproducts to be used in agricultural applications, similar to traditional, commercially available products, because this practice reduces energy consumption and pollution from the manufacturing of commercial chemical fertilizers and saves landfill space. Fertilizers permitted by the MoFCB may be exempted from obtaining a land application permit under the Missouri Clean Water Law. Fertilizer distributors must first obtain a permit through the MoFCB for the material. The source facility or distributor must then apply for the Department’s fertilizer permit exemption and receive approval from the Department prior to land applying these materials. To apply for this exemption, the supplier or distributor of the fertilizer must provide the MoFCB’s fertilizer permit, nutrient and pollutant sample results for the material, and an explanation of its intended use. To maintain the fertilizer land application permit exemption, the fertilizer material must remain largely unchanged, with no increase in types or quantities of pollutants, and the exemption request must be regularly updated according to the terms and conditions of the approval.

Fertilizer is intended to supply essential nutrients for plant growth. For stormwater associated with the land application of this material to be considered agricultural stormwater, the land must be used for the cultivation and tillage of soil, and for the production, growing, raising, and harvest of agricultural commodities and livestocks (crops, forage, and pasture). Fertilized fields may not remain bare or lack growth except as part of an agricultural farm plan, and then, may remain barren only temporarily.

Land Application Rates

Application rates are established based on nutrient content and nutrient needs, maximum concentrations of all pollutants of concern, maximum accumulation levels of relevant pollutants, and hydraulic (water-based) loading rates. The lowest calculated application rate must be used. To calculate the maximum fertilizer application rate, consider the following criteria, calculate application rates, and use the most stringent or restrictive land application rate:

• Hydraulic Loading Rate. The hydraulic loading rate is based on the maximum amount of water or liquid that may be applied before the soil becomes saturated and liquid runs off the application area. For liquid fertilizers, the recommended design hydraulic application rate is one and six-tenths inches (1.6") per day or 3.0" per week. Runoff should not occur from land application fields.
• Nutrient Loading Rate. Application rates are based upon the nutrient content of the soil (soil samples), the nutrient content of the fertilizer, and the nutrient needs of the intended crops.   
  • Soil nutrient content should be based on site-specific soil sampling.
  • Information on the nutrient needs of specific crops may be found in University of Missouri Extension Guide WQ430 Crop/Nutrient Considerations for Biosolids or from publications by other land grant universities in adjoining states. The amount of nutrient applied should be based on the crop planted and the expected crop yield; crop yields must be realistic. If no actual field-specific data is available, county average crop yields should be used, which are available online through the USDA. 
• Pollutants. The fertilizer permit exemption letter may limit the application of the fertilizer based on pollutant concentration levels. Common pollutants of concern that may limit application include pathogens, chlorides, and oil and grease.

Land Application Recommended Practices

 Agricultural stormwater runoff may not enter waters of the state and cause harm to human health, the environment, or designated uses of the receiving waterbody. The following recommended practices are provided to help prevent runoff from agricultural fields:

• Vegetated buffers (grass strips) should be established around application fields to prevent runoff onto adjacent properties and waters of the state. Land application should be at least 50 feet from property lines.
• Liquid should not run off of the application area during normal application activities. Land application fields should be checked daily during land application for runoff or signs that runoff has occurred. Sites that utilize spray irrigation should monitor for the drifting of spray across property lines.
• Fertilizer should be applied evenly over the distribution area.
• No land application should occur when the soil is frozen, snow covered, or saturated. There should be no application during a rain event or if significant rain is forecasted within 24 hours of a planned application.
• Reduce application rates when liquid fertilizer is applied on sloped fields.
• This permit exemption is not applicable to land application of animal manure. If you have any questions or concerns about land application activities in your area, please contact your regional office: