By Hannah Ruth Tabler, NFU Intern
Soil amendments are a common way to improve the development of produce. While they may help your plants grow and reduce soil erosion, they can also present a safety risk. By assessing soil amendments and implementing a safety plan, growers can avoid contamination of their produce.
The term “soil amendment” refers to any chemical, biological, or physical material added to soil for the improvement of plant growth and development. While chemical and physical soil amendments can pose some risk, the Food Safety Modernization Act (FSMA) Produce Safety Rule is mostly focused on risks associated with biological soil amendments. That’s because they contain biological materials that are more likely to carry contaminants. Some common examples of biological soil amendments include:
- Non-Fecal Animal Byproducts
- Peat Moss
- Pre-Consumer Vegetative Waste
- Sewage Sludge Biosolids
- Table Waste
- Agricultural Tea
- Yard Trimmings
Biological soil amendments break down into two areas: those that are of animal origin or those that are vegetative or green waste. Biological soil amendments of animal origin include both manure and non-fecal animal byproducts. In general, biological soil amendments of animal origin are considered riskier than green waste. However, these amendments are safe to use if they are used responsibly.
Human waste is the riskiest form of soil amendment when it comes to those of animal origin. It is not allowed to be used on produce crops unless it is a biosolid that meets EPA requirements. Untreated human waste is a high risk because it is the most likely to contain human pathogens..
Untreated manure from other animals, or raw manure, is the next riskiest choice of soil amendment. All manures can carry human pathogens, though other animals are less likely to carry them than our own waste. But manure is still a valuable and cost-effective way of improving soil health. The Produce Safety Rule just requires that special care be taken with animal byproducts that are untreated. Untreated soil amendments of animal origin must not be directly applied to the harvestable portion of the crop. Additionally, while FSMA does not have a required application interval to wait between applying untreated amendments and harvest it is recommended to use the National Organic Program’s guidelines of 90 days for produce where the edible portion does not have direct contact with the soil, and 120 days for produce were the edible portion has direct contact with the soil. Besides raw manure other examples of untreated soil amendments of animal origin include: manure, aged manure, untreated slurry, agricultural teas from raw manure, and other untreated products such as bone meal and blood meals that have not gone through a validated process to reduce pathogens.
To reduce the risk of soil amendments of animal origin besides following the recommended application process and wait time a grower could choose to use a treated soil amendment. Soil amendments of animal origin can be treated through composting or heat treatment to reduce the presence of potential pathogens. Under the Produce Safety Rule only a composting process that has been scientifically validated to reduce pathogens may be used. There are two examples of these processes provided under the rule but others may be used if shown to be scientifically validated. Treated soil amendments of animal origin have a zero day application interval between applying and harvesting. The recommended application method may vary pending on the composting method used.
Returning to vegetative or green waste –these are considered to be safer than biological soil amendments that contain animal byproducts whether treated or untreated. Under FSMA, solid waste that is purely vegetative in origin is called “pre-consumer vegetative waste”. This includes produce food preparation waste, out of date vegetables, and food products removed from their packaging. In general yard trash, table waste, and restaurant waste is not considered to fall under this as it may have come in contact with meat or animal waste. While pre-consumer vegetative waste is considered less risky from a biological standpoint, it can still contain chemical or physical hazards,
Non-biological or chemical soil amendments have a minimal risk of carrying human pathogens. They are considered the least risky soil amendment. But be aware that this too can pose a chemical risk if used irresponsibly. Workers should receive proper training before using chemicals of any kind on the farm. Regardless of your choice in soil amendment, risks can be managed through treatment, application timing, and application method. By managing the use of soil amendments, the risk of produce contamination can be lowered. Excessive use and/or misuse of amendments should be avoided for the production of safe and healthy produce.
What soil amendments do you use? Stay tuned for more on risk prevention in the use of soil amendments soon.