The Soil Food Web- Mulch, Compost Tea &, Mycorrhizal Relationships

As we understand that the soil food web is the foundation that creates the soils needed to support healthy, sustainable plant life, we will explore the importance of fungal compost, compost tea and mycorrhizal fungi and their relationships with the soil food web and maintaining trees, shrubs and perennials.

Just a reminder, trees, shrubs perennials prefer their nitrogen in forms of ammonium, not nitrate.  If you have ever wondered why your picea pungens (blue spruce) did not survive in the middle of your turf grass, the major contributor probably was your turf grass lawn as it is nitrate-fertilized.  By early detection or knowledge, you might have been able to protect your spruce by creating negative lawn area, in this instance, a planting island.

Mulches, fungal compost and tea work best on maintaining the health of your shrubs, trees and perennials.  When applying amidst your trees, you’ll want to make sure there is negative space between the compost and the trunk so the microbes aren’t in contact with the trunk, so the microbes don’t attack the bark.  It also makes perfect sense, both now and for future maintenance, to create planting or greenspace under the trees in place of turfgrass.

If you look at nature, leaves fall and cover the roots, naturally recycling the nitrogen and carbon with some making it back to the plant.  By applying a form of mulched leaves within a layer of brown mulch, preferably a couple inches thick, it will provide slow release nutrients and protect the roots though the winter months.  By applying a compost tea in the fall and once again in the spring (about 2-3 weeks before your shrubs and trees leaf out) is a sustainable way to insure the health and integrity of your plants and trees.

Mycorrhizal fungi products have been around for nearly a century but have mainly become main-stream within the last 5 years.  It is a natural form of nitrogen, one that envelopes and takes hold on the roots of your plants and is created by plants.  Hardwood trees form mycorrhizae known as ectomycorrhizal where most shrubs, perennials and softwood trees form mycorrhizae with endomycorrhizal fungi.  The heath family, which includes rhododendrons, sub-specie azaleas and blueberries, thrive on mycorrhizal fungus. 

If your garden is mature and you have compacted soils without noticing mycorrhizal activity (mushrooms growing under the drip line of your trees) you may wish to use a deep root feeder to inject your mycorrhizal drench to inoculate the roots.  With shrubs and perennials, it is simply excavating around their drip lines into their root zones with a spade or trowel and applying Endomycorrhizal spores.  If you have mushroom growth in and around your trees drip lines, then your soil has not been degraded to the point where natural mycorrhizal has been effected and you don’t necessarily have to add to create one.  Mycorrhizal fungi spores must be in contact with roots within 24 hours after exposure to moisture to grow and this is why mycorrhizal fungi is applied as a drench to assist in their delivery.

By applying mulches, teas, composts and mycorrhizal, your trees, shrubs and perennials will be less stressed and keep them from becoming attacked by insects.  They create extra pitch; their leaves are coated with beneficial bacteria and fungi to outcompete disease.  By having a soil food web –based system in place, you will continue to build a sustainable foundation for a healthy garden and greenspaces. If your plants do become stressed or diseased, at the first sign, don’t hesitate to put your soil food web knowledge to use and re-apply, especially compost teas. 

The Soil Food Web & The Relationship to Healthy Soil

To support sustainability, a good foundation is necessary.  Just as important as a well constructed building foundation, the soil food web is the foundation that creates the soils needed to support healthy, sustainable plant life.

Good soils are teeming with life, from earthworms to centipedes and ants, there is a world of soil organisms such as fungi and bacteria in which every organism needs energy to survive.  They derive this energy from nitrogen and sulfur and carbon that is produced from plants and waste products produced by other organisms.  The soil food web, beneath and above the soil is simple eat and be eaten existence.  Organic matter produced by healthy plants and root systems create organic matter that is turned into bacteria (subsurface) while fungi is being created closer to the soil surface.  In a cross-linked soil food web, root and fungal feeding nematodes are then preyed upon by birds which in turn are preyed upon by larger animals.  To simplify, it always starts with the plant.

Plants secrete chemicals that are important to the soil’s condition, through photosynthesis in the leaves and these secretions are referred to as 'root exudates'.  These carbohydrates exudated by roots grow beneficial bacteria and living fungi which commences the food web.  These beneficial bacteria and fungi are natural fertilizers for healthy plants and are spread by nematodes by eating the bacteria and fungi, digest what they need to survive and excrete excess carbon as waste.

As we gardeners all know, not all soil bacteria and fungi is beneficial and many cause plant diseases.  Having good soil food web containing a large, diverse population of different species will help control theses non-beneficial troublemakers.  This healthy soil food web will keep these pathogens in check and in some instances to their deaths.  Mycorrhizal fungi is a special soil fungi, interacting with roots, producing nutrients such as water, nitrogen and phosphorous.

The importance of understanding the soil food web, the foundation of good soil, is to also understand the negative impacts on the soil food web.  Chemical fertilizers, pesticides and insecticides affect the soil food web in a negative way, toxic to some and chasing others away.  You have now started altering the soil food web as you will have to continue to use chemical fertilizers and pesticides as plants microbial method of obtaining nutrients has been affected by reducing the natural fungi and bacteria and chasing away a major contributor, the earthworm. 

The living organisms within the soil food web will be continuously at work, building defenses against pests and disease, creating soils that drain well and pathways for oxygen and carbon dioxide.  By employing soil food web knowledge, you can reduce / eliminate the use of commercial chemicals and fertilizers, improve your soils overall health and usefulness and start building a sustainable foundation.

Next blog release, we will discuss the soil food web and its important relationship with compost tea, mycorrhizal and maintaining trees, shrubs and perennials.