Home Soil Testing for E. Coli

Vegetables in gardens that have been fertilized with manure can be contaminated. Remember to thoroughly wash raw fruits and vegetables before eating them. You can check for E.coli at home by taking a soil sample and using a test kit.

Produced by the Department of Communications at Kansas State University. For more information, visit our website at: http://www.kansasgreenyards.org

Transcript:
Home Soil Testing for E. Coli

Once you’ve got your soil and water mixture from doing the pH and the nitrate test, you can use that same water to do the E.coli test. You’ll need a sterile pipette, which you can get from your county extension office, or you can use just a clean medicine dropper. You’ll need one milliliter of liquid, which in this pipette is just the stem. It’s a very small amount of liquid.

You’ll need to draw it up into the pipette, and then lift the cover of the plate, and then slowly squirt it onto the plate, roll the cover slip down, and then gradually tip it to make a nice even sample. In a few minutes, this will jell up, and then you need to wait between two and three days for this to develop. E.coli is a bacteria, and what we’re looking for are colonies of bacteria.

Some plates that I’ve already developed from samples at home will demonstrate the color differences. With these plates, the one with pink dots is showing normal soil bacteria, and that’s OK. I wouldn’t want it in my drinking water, but for soil samples, this is very normal.

What you don’t want are the blue dots. If you have blue dots, each one of those is an E.coli bacteria that grew into a colony. That means that you have contamination in your soil, and splash from the soil could get on your salad greens, or your other vegetables or root crops, and potentially be harmful.

So, this would not be good for spinach. The longer the soil sets, the more the bacteria will die. So, if it’s springtime and you have E. coli when you’re planting tomatoes – by the time your tomatoes are ripe, you should be fine. UV light from the sunlight, and drying out the soil will kill these bacteria. But if you’re growing spinach or salad crops such as beansprouts, this is a good test to do at home to check and see what is going on in your garden.

This feature story prepared with Rhonda Janke, Kansas State University Research and Extension, Sustainable Cropping Systems. For more information, visit your local county extension office or visit our website at KansasGreenYards.org.