Irrigation water quality

Do you produce crops that are consumed fresh? If so, do you use surface water to irrigate these crops? Or has your buyer requested irrigation water quality records? If you answered yes to these questions, then read on.

It is important to know what you spray on your crops. History tells us that water is an excellent source for disease, either directly through drinking, or through using water in food production. Bad bugs can exist in our water, and poor quality irrigation water has caused a number of food borne outbreaks.

OMAFRA has done research on irrigation water and strawberries and found that irrigation water, which exceeded the guideline of 100 coliform forming units (cfu) of E. coli per 100 mL of water, transferred E. coli to the berries. What does the presence of E. coli mean? Feces! The presence of feces on our food is not a good thing, particularly as pathogens come from feces.

To avoid contaminating your crops with bad bugs from irrigation water we recommend that you test your irrigation water for quality.

How do you do this? Contact a lab in your area and ask whether they do E. coli testing for non-residential water (if you do not know of a lab you can search for one on the Standards Council of Canada - Directory of PALCAN Scopes website.

Let the lab know that you will be submitting at least two non-residential water samples for E. coli analysis (coliforms will likely be included). The lab should be able to provide you with sterile bottles to obtain the samples. To take the samples:

• Run the water through the irrigation system for at least 20 min to flush the lines
  
• Obtain at least two samples, as microbial levels can fluctuate
  
• Obtain the samples from the sprinkler system and ensure that water in the bottle has not contacted other surfaces that may contaminate the water such as bare hands and sleeves

Once you obtain your water results, focus on the E. coli results only. Ideally, E. coli should be less than 100cfu/100mL. What if the results exceed 100cfu/100mL? Keep in mind that water quality fluctuates with weather and surrounding activities, therefore, if the results did not exceed 1000cfu/100mL, another water test may produce results that are within the guidelines. Regardless, here are a couple of ways to reduce the risk:

• Reduce water contact with the edible portion of the crop, such as with drip irrigation. This will also help conserve water.
  
• Extend the time between irrigation and harvest. The longer that these microbes are exposed to solar radiation and drying, the less will survive on crop.

Reducing the risk from irrigation involves awareness and action: Awareness of the quality of your irrigation source and whether the crops you produce can be consumed raw; and action, which will depend on the type of crops you produce and the quality of your irrigation supply.

If you would like more information on the safe use of irrigation water for fruits and vegetables, consider signing up for our workshop that guides you through a risk assessment of water sources and guidelines for microbiological safety. Other workshops offered include Post-harvest Water, Manure and Composts, and Hygiene and Hand Washing. Call 1-866-641-3663 to register.

Learn more:

• Standards Council of Canada - Directory of PALCAN Scopes
• Improving On-Farm Food Safety Through Good Irrigation Practices, OMAFRA Factsheet No.05-059
• On-Farm Food Safety, OMAFRA website\