Using Soil Microbes in Plant Foods

Most of us grew up with a very rudimentary understanding of what plants need to grow. We understood that plants need nitrogen (N), phosphorus (P) and potassium (K)—and a few other things, too, of course. But the N-P-K ratio somehow became the end all, be all of plant nutrition. So much so that plant food/fertilizer products usually emblazon that N-P-K ratio front and center on the packaging.

What plants need to not only survive and thrive is becoming better understood not only by researchers but also by plant professionals and the general gardening public. For example, there is a whole ecosystem of organisms in the soil that feed and nurture plants. This complex system of organisms is known as the soil biology. And while scientists still have a long way to go to understand the relationships between these microscope organisms and the plants themselves, we already have a working knowledge of it. Enough, at least, to allow us to apply it to our gardens.

For many years now, manufacturers of plant foods have been making products that include beneficial organisms. These are most often fungi that create a mycorrhizal relationship with the plant’s root system. There are other bacteria and fungi manufacturers have been using that also aid in a plant’s nutrient and water uptake and protect the plant from pathogens in the soil.

An important aspect of these biological additives for plants that home gardeners should be aware of is that these additives work best if they are in direct contact with the plant’s root system. That way these microbes have the best chance of forming a biological connection with the plant. This can be done in two ways, as exhibited by two products with which I’m familiar. The first is the Bio-tone Starter! Plus from The Espoma Company. (Bio-tone is Espoma’s proprietary combination of beneficial microbes.) This granular product is added into the planting hole when the plant goes into the ground. The second product is something called the Fuhgeddaboudit Root Zone Feeder Packs from Organic Mechanics (pictured above). These feeder packs contain mycorrhizae (along with a bunch of other ingredients) and are added into the planting hole at time of planting. The addition of water right after planting (with both products) is want activates the microbes to begin their jobs of connecting with the plant’s roots.

That last part – activating with water – is important. If these microbes are in a soil or compost or planting mix that has some moisture—and therefore also some active organisms such as algae or moss—it’s more than likely that those algae or moss will activate the soil microbes before the gardener can use it in the ground. Essentially, the microbes in the package are used up before they get added to the ground. So, watch for products that contain soil/compost mixes and claim to have added microbes. Also, stay away from microbe-containing products that have been stored in full sun or exposed to rain at your garden center. Again, the microbes may have been rendered ineffective.

There are some products on the market that do combine the microbes with a planting mix. In these cases the microbes have been encapsulated to protect them until activated at planting time. There are also some liquid plant foods that contain these encapsulated microbes. Again, they’ve been encapsulated to protect them from the liquid solution.

So, if you’re hoping to change up your fertilizing game with year, perhaps consider using a product with a little biology thrown in.

Meet Ellen Wells

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