Because the micorrhizas are living organisms they can and do die, so the concern is to avoid those activities in the garden that will kill off the beneficial organisms. They live in communities in your soil, so breaking up their communities by rototilling can kill them. Excessive salts kill them and alkaline soil is not a good environment for them. Excessive salts enter the soil through concentrated fertilizers as compared to compost or other raw ingredients. This is why organic gardeners are so vehement against “chemicals” in the garden. Chemicals will kill the micorrhizae.
A low micorrhizae count will result in stunted plants or plants that require more fertilizer to reach full size. Without micorrhizae, plants will have a lower immunity to disease and be more susceptible to insect attacks. In my gardens that have healthy soil, I don’t get aphid attacks. I can tell which beds need more compost or a treatment of micorrhizae by whether or not aphids are attacking the cole crops.
My imported soil has not had healthy levels of micorrhizae. It has just been too mixed and manipulated for communities of beneficial organisms to grow, so I’ve developed several sources of beneficial bacteria and fungi to add to my soil. I tried buying fungi from Fungi Perfect. The inoculants came in a powdered form that I sprinkled in the ground with my transplants. I’m not certain it did much good. My best source of good things for the garden comes from the duck pen. Bedding mixed with manure is good. The ducks mix a little bit of everything into their water buckets. Everyday, when I change their water, they’ve given me half a bucket full of murky, disgusting sludge that when dumped on a garden works miracles. Especially in the warmer weather things start growing in the duck water fairly quickly.
Manure tea is another source of beneficial bacteria. It is much like my duck water. One concern with manure tea has been that most of the bacteria are anaerobic. Some think aerobic bacteria are better for the soil. I’m not certain which theory in the Anaerobic VS Aerobic debate is right or if there is a true difference. However, I did buy a pump for making aerobic “manure tea’. The process is a little more challenging than regular manure tea where you throw a shovel of duck bedding or a cow pie in a five-gallon bucket and let it sit. Aerobic manure tea adds oxygen to the five-gallon bucket with a little pump that works much like the pump for a fish tank.
The aerobic process is a little more dramatic than the anaerobic-let-it-sit process. When the aerobic tea starts to work, it produces a lively head of foam that spatters all over the wall near the outlet where the pump is plugged in. The instructions that came with my aerobic set up included a recipe of compost plus a high nitrogen source. The Soil Soup company suggested buying their ingredients rather than using a little duck water and some litter from the duck yard. I suppose people who don’t have farm animals might need to buy ingredients.
My other source of fertilizer and microbes for my gardens comes from my big ponds. In the heat of the summer the ponds turn green and skuzzy. I can hook a hose to the pump for the fountain and water my gardens with the pond water that is full of fish poop and anything the ducks have deposited in the ponds, plus whatever decided to grow.
Once a garden starts growing its own community of micorrhizas, all one needs to add is organic matter. There is no need to inoculate every year. Some of my older beds do just fine without the duck water or other amendments other than the leaves that fall from the plants. Once established, beds of healthy soil do not need much water or added fertilizer. Healthy soil that doesn’t need amendments really saves the grower a small fortune while producing an abundance of food and flowers.