He doesn't go into details. This is all he says, "
Used soil - Reusing soil has a few downsides such as it makes it easier for diseases, viruses, and pathogens from entering your garden. Also peat based soils break down and become acidic. If you fertilize with chemicals you'll end up with salt buildups that will slow growth. Unless you like to take chances, have a good eye, and a good horticultural understanding, you may be better off with staying with fresh new soils. That said; I grow strictly organic and I've always reused my soil. I don't sterilize the soil between plantings as my soil is full of microbes and predatory bugs that keep the bad bugs under control. After each crop, I chop up the soil and root balls with the leaves, stalks, etc and let compost for about 3 months. I then mix it up and add about 2 - 3 cups of lime for every 50 gallons composted soil. I also add about 1/2 cup epsom salts, 2 liters bone meal, 1 liter blood meal, 1 liter kelp meal, 1 tsp trace elements, and enough perlite to regain the porosity of the original soil. I used to add a bag of manure, but I was getting fertilizer burn and so have stopped now.
As I've been fine tuning this, the plants just keep getting healthier and I haven't had any real pest problems for quite a while. I know this is a controversial approach and maybe even risky, but it allows me to keep my garden pretty much self contained. I don't attract attention by buying bales of soil every 3 - 4 months year around, or in the disposal of leaves and soil after each crop. It's definitely not for those who want sterile crops and those that use pesticides and chemical ferts. I believe in working with nature, not against it. After several generations, a nutrient imbalance developed which was only solved by leaching the soil thoroughly. My hunch is that one of the micro-nutrients was building to toxic levels. I guess farmers don't get this problem because they have the winter rains to leach excess nutrients from their fields."
