Dealing with irrigated crops and food safety

When implementing irrigation practices to produce crops, growers should be mindful that the water being used doesn’t contaminate produce with food-borne illnesses.

The unpredictable nature of weather makes irrigation a necessity with some crops. How you irrigate can have a dramatic effect on food safety. Where food safety is concerned, Michigan State University Extension advises a number of considerations that must be planned for when irrigating crops.

Method of irrigation

With all other risk factors being equal, overhead irrigation poses the most risk of contaminating a crop. Surface irrigation, such as exposed drip tape on top of the soil, is less of a contamination risk. Finally, irrigation delivered in a closed system, such as buried drip tape or drip tape under plastic, poses almost no risk of contamination.

The difference is so profound in level of risk that it is reflected in the Food Safety Modernization Act requirements. Water that is applied overhead or via a method where water may contact the plant must be tested and kept under a certain threshold. Water that is applied under plastic or through buried drip tape has no such requirements.

Plant growth stage

If the plant is in a vegetative state or is more than a month from harvest, then there is a relatively low risk of contaminating the crop. If, however, the crop is within two weeks of harvest or there are fruit present on the plant, the risk of contamination is increased significantly.

Water sources

Municipal and well water sources are the safest in terms of potential contamination. Ponds are an intermediate risk while rivers and streams pose the greatest risk to contamination.

It’s important to remember that risk is a reflection of how easily an existing pathogen can get through to the crop after harvest. Just because you utilize a high risk source, method or plant growth stage does not mean you are destined to contaminate the crop. If you employ a water test and it shows low or no generic E. coli numbers, then there is little chance of contamination.

Understanding irrigation water risks is complex and very specific your farm’s practices. If you have difficulty understanding your risk, contact the Agrifood Safety Work Group at or 517-788-4292. To obtain more information about irrigation water risks, ask for guidance document AFSM033-01.

Did you find this article useful?