Most fertilizers that are commonly used in agriculture contain the three basic plant nutrients: nitrogen, phosphorus, and potassium. Some fertilizers also contain certain "micronutrients," such as zinc and other metals, that are necessary for plant growth. Materials that are applied to the land primarily to enhance soil characteristics (rather than as plant food) are commonly referred to as soil amendments.
Fertilizers and soil amendments can be derived from:Overuse of fertilizers has resulted in contamination of surface water and groundwater.
Biosolids are nutrient-rich organic materials resulting from the treatment of domestic sewage in a treatment facility. When treated and processed, these residuals can be recycled and applied as fertilizer to improve and maintain productive soils and stimulate plant growth. Biosolids are treated sewage sludge. Biosolids are carefully treated and monitored and must be used in accordance with regulatory requirements.
EPA offers guidance and technical assistance for the beneficial recycling of biosolids as soil amendments and fertilizer. The use of these valuable materials can enhance:
Sewage sludge that is used in agriculture is regulated under the Clean Water Act, and is currently subject to concentration limits for the following metals:
Agricultural producers can return manure and crop residues to the soil as fertilizers or soil conditioners on their own property unless prohibited by other State or local laws.
Sources and Solutions: Agriculture - Animal manure, excess fertilizer applied to crops and fields, and soil erosion make agriculture one of the largest sources of nitrogen and phosphorus pollution in the country.
Estimated Animal Agriculture Nitrogen and Phosphorus from Manure - Animal agriculture manure is a primary source of nitrogen and phosphorus to surface and groundwater. Manure runoff from cropland and pastures or discharging animal feeding operations and concentrated animal feeding operations (CAFOs) often reaches surface and groundwater systems through surface runoff or infiltration.
Commercial Fertilizer Purchased - Fertilizer is a primary source of nitrogen and phosphorus. It often reaches surface and groundwater systems through farm or urban/suburban runoff or infiltration. Fertilizer use and run-off can be significantly reduced by appropriate fertilizer application through:
The USDA Agricultural Research Service has patented a new technology that can remove ammonia from livestock wastewater and recycle it as a fertilizer.
Industrial waste materials are often used in fertilizers as a source of zinc and other micronutrient metals. Current information indicates that:
Some fertilizers and soil amendments that are not derived from waste materials can nevertheless contain measurable levels of heavy metals such as:
EPA's longstanding policy encourages the beneficial reuse and recycling of industrial wastes. This includes hazardous wastes, when such wastes can be used as safe and effective substitutes for virgin raw materials. EPA is examining whether some fertilizers or soil conditioners contain potentially harmful containment levels. However, the Agency believes that some wastes can be used beneficially in fertilizers when properly manufactured and applied.
Concerns have been raised regarding the use of certain wastes in the manufacture of agricultural fertilizers and soil amendments, and the potential for ecological or human health risks, as well as crop damage, when such fertilizers are applied to farmlands.
For fertilizers that contain hazardous waste, EPA standards specify limits on the levels of heavy metals and other toxic compounds that may be contained in the fertilizer products. These concentration limits are based on the "best demonstrated available technology" for reducing the toxicity and mobility of the hazardous constituents. However, fertilizer made from zinc-containing hazardous secondary materials are instead subject to the conditions of the zinc fertilizer exclusion found at 40 CFR section 261.4(a)(20). The zinc fertilizers made from hazardous secondary materials are excluded under 40 CFR section 261.4(a)(21). In order to be recycled to make fertilizers under these provisions, these materials must meet all the conditions of these exclusions, including contaminant limits for heavy metals.
In some States, the regulations on hazardous waste use in fertilizers may be more stringent than the Federal standards, since States can adopt regulations that are more stringent and/or broader in scope than the Federal regulations.
For food chain crops, farming can occur on land where hazardous constituents are applied as long as the agricultural producer receives a permit from the EPA Regional Administrator. Agricultural producers must demonstrate that there is no substantial risk to human health caused by the growth of such crops.
Unless prohibited by other State or local laws, agricultural producers can dispose of solid, non-hazardous agricultural wastes on their own property. This includes: