When assessing food safety risks on your farm, it is important to understand current production practices as well as prior land use. You should consider biological, chemical, and physical risks that may result from current and past uses such as animal feed lots, septic systems, or if the land was previously a building site or dumping ground. In addition to your own farm, adjacent land uses should be considered. Whether the surrounding land is occupied by private homes, animal production farms, wooded areas, or a bustling city, there is potential for food safety risks to be present. Contamination of crops, soil, and water sources has resulted from leaking septic tanks, runoff from animal production farms, and fecal deposits from wildlife that enter fields. Being aware of current and past field uses as well as adjacent land use will help you develop practices that reduce any food safety risks that may exist.
To begin evaluating your farm’s land use risks, you should consider drawing a map of your fields and land features. Be sure to include man-made structures such as animal pastures, irrigation systems, ditches, and roads, as well as natural topography. The map should include key pieces such as:
- Crop production and packing areas. You should make note if these areas were previously used in ways that could introduce biological, chemical, or physical hazards.
- Field sanitation units (e.g., Porta-Potties and handwashing stations)
- Location of active wells and septic systems
- Surface water sources such as streams, rivers, or ponds
- Areas that are prone to flooding
- Raw and composted manure storage sites/composting areas
- Animal pasture areas and/or barns where animals are kept
- Chemical storage areas
- Nearby land uses such as animal operations on neighboring farms, including distances from fields and potential impact on water sources used by your farm
It may also be helpful to include these things on the map so that they can be incorporated into your overall farm food safety plan to support production logs, traceability, and other produce safety related practices:
- Soil and drainage maps
- Copy of field records and growing history
- Physical address or GPS location of the farm
- Names of roads that form farm borders
- Name or number you assign to each field and water source for traceability practices
To minimize food safety risks, crop production areas and water sources should be a sufficient distance from any septic systems and raw manure sources, which include animal production farms, manure containment areas, and composting facilities. Septic systems and soil amendment storage areas must be located and maintained in a way that prevents contamination of produce fields, water sources, and produce packing/holding areas (1,2). While there is no conclusive research that validates exact set back distances needed between fields and potential sources of contamination, this decision tree uses recommendations from the California Leafy Green Marketing Agreement (3).
Recommended set back distances can be adjusted depending on characteristics of your farm related to topography including land slope, physical barriers such as trees or grass-covered land, wind patterns, and other attributes such as the number of animals present. For example, if the field is located on top of a hill and a dairy operation is downwind and at the bottom of the hill, the risk is minimal and the recommended set back distance may be decreased. Physical barriers such as wind breaks, berms, vegetative buffer strips, containment structures, and ditches can prevent runoff from contaminating crops and the recommended set back distances may be decreased. High concentrations of wildlife (e.g., deer, waterfowl) or domestic animals (e.g., cows, sheep, horses) increase the contamination risk because they can harbor harmful pathogens in their feces (4). If wildlife activity is high and fecal material is present, you must assess the areas used for growing covered for evidence of potential contamination produce and determine whether the produce can be safely harvested (5, 6) (see also the Wildlife and Animal Management Decision Tree). Keep in mind that with more animals present, there may need to be a greater set back distance between the animal habitat and the produce fields. When assessing the risk of manure sources near water sources, consider the distance from the manure source to the water and any ditches, canals, or land slope issues that feed the water source.
If your land is prone to flooding, you should consider the risks present to the crop and water sources. There are two types of flooding. The first occurs after a heavy downpour when fields become saturated and water pools on the soil surface. This type of flooding can reduce yields and even kill plants, but does not necessarily introduce water from surrounding areas that may contain contamination. The second type of flooding occurs when runoff from the surrounding areas or surface waters, such as rivers, lakes, or streams, overflow and run into fields. Flood waters, as described in the second scenario, are more likely to contain chemical and biological contaminants that may be harmful to the health of humans and animals. Since flooding can cause septic systems to overfill and leak, you must monitor these systems to ensure they do not contaminate the surrounding areas (1). According to the FDA, edible portions of crops that are contacted by this type of flood water, including runoff from surrounding areas and septic systems, are considered adulterated and cannot be sold for human consumption (7).
Awareness of previous and nearby land use will help you to assess risks on your farm. There are many actions that can be taken to reduce identified risks such as planting agronomic crops in higher risk fields or extending buffer areas between nearby lands and produce fields. Remember, the focus should be on risk reduction since you can never completely remove all risks.