Soil microbes play an essential role in releasing nutrients from the soil in a form that our fruit trees and other plants can access. So, if your soil doesn't have a healthy and diverse microbe population, your fruit trees will not thrive. The problem is that microbes are so tiny that we can't see them with the human eye. How do we know if we have a good microbe population? According to the Soil Conservation Council of Canada all you have to do is bury a pair of 100% cotton underwear in the topsoil of your garden. Leave your undies in the ground for a couple of months. Then, when you dig them up see what they look like. If your soil microbes have been busy digesting and recycling organic matter, then all that will be left is the elastic waist band.  To learn more about this process, I've invited two experts from the University of Guelph to talk about the "Bury Your Briefs Campaign" and about the role soil microbes play in keeping our fruit trees and other plants healthy. They are Cameron Ogilvie, Knowledge Mobilization Coordinator and Kari Dunfield, Canada Research Chair in Environmental Microbiology of Agro-ecosystems.  This month's contest prize: a U of G baseball cap and trowel.Learn to grow organic fruit trees successfully. Sign up for OrchardPeople.com's premium online courses at https://learn.orchardpeople.com/.