Should I Apply Waste or “Byproducts” on My Farm?

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Farmers in some parts of North Carolina may have an opportunity to utilize waste materials or by-products from another operation as a source of nutrients on their land. Manure from large-scale livestock operations is an obvious example, but other industries can also produce by-products that have value when applied to farm or forest land. The material may be available at a competitive cost compared to conventional fertilizers, or perhaps even at no cost to the farmer or landowner. These opportunities may seem especially attractive when fertilizer prices are high. The information in this article is intended to help farmers and landowners weigh the pros and cons of their use, and to get maximum benefit when they decide to use them.

In general, the application of such materials is regulated by the North Carolina Department of Environmental Quality. Among other things, the regulations are designed to protect water quality, including streams, lakes and groundwater. For example, the regulations would help protect against nitrate leaching into the groundwater near the application site.

Such materials may contain various beneficial components, including:

  • major nutrients such as nitrogen, phosphorus and potassium
  • micronutrients
  • organic matter
  • liming material

Farmers who are considering this type of material should keep several things in mind.

1. GET A NUTRIENT ANALYSIS ON THE MATERIAL – The supplier may have general data on the components in a given material, but farmers should be certain to get a nutrient analysis of the specific material that arrives on their farm. Such an analysis can be obtained at minimal cost by submitting a sample to the NC Department of Agriculture & Consumer Services (NCDA&CS). The analysis will show quantities of nitrogen, phosphorus, potassium, certain metals, and also the liming properties (CCE or calcium carbonate equivalence). For details, see the Waste/Compost Analysis information on the NCDA&CS webpage.

2. APPLY THE MATERIAL TO MEET CROP NEEDS – Just as with conventional fertilizers, the material should be applied at a time and rate matched to crop needs.

3. ADDITIONAL FERTILIZERS MAY BE NEEDED – Likely in most cases, a given material will not meet all the nutrient requirements for a particular crop. Thus, the producer will need to supplement with nutrients from another source such as conventional fertilizers.

4. MONITOR CHANGES WITH REGULAR SOIL SAMPLING – In normal cases, farm fields should be sampled every 2 or 3 years. However, use of by-product materials may warrant annual soil sampling, especially if materials are used on a recurring basis. This will allow farmers to be certain that nutrients, pH and metals do not rise to levels that are detrimental to plant growth. Applications should be discontinued before that point is reached.

5. CONSIDER SOIL COMPACTION – Application of such materials is normally done with large tractors that are carrying or pulling a tank with many gallons of material. Each time a large piece of farm equipment travels over a field, soil compaction increases by a small increment. This effect is mitigated to some extent by the use of additional tires and/or tires with larger surface area that spread the weight. However, at some point it may be necessary to use a chisel plow or other implement to break up compaction, at additional expense to the farmer.

6. FIND OUT BUFFER REQUIREMENTS  – The permitting authority will normally specify buffer requirements, i.e. avoiding application within a certain distance of homes, streams, ponds, roadways and other sensitive sites. The material supplier or permitting authority can advise you on those requirements.

7. CONSIDER MONITORING THE APPLICATION – If the material supplier is responsible for applying the material, consider being on-site during the application. That way the farmer/landowner can be certain it is done as agreed, or quickly make corrections before problems occur.

8. APPLY TO ALLOWED SITES/CROPS – Most of these materials can be applied to sites such as pastures, woodlands, and row crops (e.g. grains such as wheat, soybean and corn). Application to fruit and vegetable crops would be restricted due to a risk of microbial contamination. However, fruit and vegetable crops could potentially be grown in a treated field after a mandated waiting period. The waiting period is normally specified as a number of days between application of the material and harvest of the crop to be grown, with 120 days being a typical minimum. Details should be available from the material supplier and/or the permitting authority.

9. GET IT IN WRITING – To avoid confusion and disagreements, the farmer might consider executing a written agreement with the supplier. Such an agreement could cover timing, rate, location, buffer areas, access routes to the field, and more. The material supplier may have a standard form that they use, but a farmer/landowner should not hesitate to bring up special requests or concerns during the discussions/negotiations.

Byproducts and waste materials may present an opportunity for farmers to obtain free or low cost crop nutrients. However, applying materials without careful consideration and research could lead to undesirable outcomes. Farmers and landowners are advised to proceed carefully and methodically so that they can get maximum benefit while protecting their interests.

For more information, see the following resources from the NC State University Crop and Soil Sciences Department:

Swine Manure as a Fertilizer Source

Best Management Practices for Agricultural Nutrients

Nitrogen Management and Water Quality

Guidelines for the Commercial Application of Poultry Litter

Waste Analysis

Dairy Manure as a Fertilizer Source

Managing Equipment Traffic to Limit Soil Compaction

Agricultural Riparian Buffers

The author gratefully acknowledges expert insight on this topic from Dr. Stephanie Kulesza and Dr. Luke Gatiboni, both with the NC State University Crop and Soil Sciences Department. That said, the author accepts all responsibility for errors or omissions, and welcomes feedback.