Land Use Decision Tree (Full Portfolio) (pdf)
When assessing food safety risks on your farm, it is important to understand current production practices as well as prior land use. Consider biological, chemical, and physical risks that may result from current and past uses such as animal feed lots or if the land was previously a building site or dumping ground. In addition to your own farm, nearby land uses need to 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 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 nearby 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, draw a map of your fields and land features. Be sure to include man-made structures such as irrigation systems, ditches, and roads, as well as natural topography. The map should include key pieces such as:
- Crop production and packing areas. 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)
- Location of active wells and septic systems
- Surface water sources
- Areas that are prone to flooding
- Raw and composted manure storage sites/composting areas
- Animal pasture areas and/or barns where they are kept on your farm.
- Chemical storage areas
- Nearby land uses such as animal operations on neighboring farms, including distances from fields and impact on any water sources used by your farm
It may also be helpful to include these things on the map so that it 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
- Road names that form farm borders
- Name or number you assign to each field for traceability practices
To minimize food safety risks, crop production areas and water sources should be a sufficient distance from any raw manure sources, which include animal production farms, manure containment areas, and composting facilities. While there is no conclusive research that validates exact distances needed between fields and potential sources of contamination, this decision tree uses recommendations from the California Leafy Green Marketing Agreement.1
Recommended 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, 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 distance may be decreased. Physical barriers such as berms, vegetative buffer strips, containment structures, and ditches can prevent runoff from contaminating crops. If physical barriers are in place, the recommended distances may be decreased. High concentrations of wildlife (e.g., deer, waterfowl) or domestic animals (e.g., cows, sheep, horses) increase the potential contamination risk because they can harbor harmful pathogens in their feces.2 If wildlife activity is high and fecal material is present, actions should be taken to reduce their activity in or around fresh produce fields and packinghouses (see Domestic Animal and Wildlife Decision Tree). Keep in mind that with more animals present, there may need to be a greater distance between the animals and the produce fields. When assessing the risk of manure sources near production 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, 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 steams, 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. According to the FDA, edible portions of crops that are contacted by this type of flood water are considered adulterated and cannot be sold for human consumption.3
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.
- Commodity Specific Food Safety Guidelines for the Production and Harvest of Lettuce and Leafy Greens. 2013. California Leafy Green Products Handler Marketing Agreement (LGMA).
- Beuchat, L.R. (2006). Vectors and conditions for preharvest contamination of fruits and vegetables with pathogens capable of causing enteric diseases. British Food Journal, 108(1), 38–53.
- FDA Guidance for Industry: Evaluating the Safety of Flood-affected Food Crops for Human Consumption.