Dr. Elaine Ingham and The Soil Food Web School

Dr. Elaine Ingham and the Soil Food Web School promote a number of controversial topics in soil management and in this post I would like to have a closer look at a number of these.

The Soil Food Web

Every organism in soil is a food source for other organisms. The soil food web is a way of trying to understand the various interrelationships between these organisms and the above drawing is a common way of depicting this web of life.

The reason for all of these interconnections is that each organism has to find a suitable energy source. This process of energy transfer is not restricted to the soil and also takes place above ground. This is emphasized in my drawing of the Energy Food Web published in Soil Science for Gardeners. The whole process starts with plants and a few photosynthetic microbes who get their energy from the sun. That energy is then transferred from one organism to the next in the web, which I called the Energy Food Web.

It is also important to note that unused energy ends up as organic matter in the soil, which is then redistributed through the whole system as another energy source.

Original ideas for soil food web were developed in the 1920s and active research has been going on for over 35 years. Even though the concept has been around for quite some time, it is a very complex system and progress in understanding it has been slow.

What is The Soil Food Web School?

The Soil Food Web School is an educational business focused on soil health and regenerative agriculture, founded by Dr. Elaine Ingham, a microbiologist and soil health advocate. Its history is deeply intertwined with Dr. Ingham’s work in understanding the complex relationships between soil microorganisms and plant health.

The school was formed in the early 2000s with an aim to teach the principles of soil biology and practical applications for improving soil fertility through understanding and managing the soil food web. With an emphasis on regenerative agriculture it has a strong focus on using compost and compost teas to balance the ratio of different microbes to meet a plants needs.

Although many of the basic concepts the school teaches are based on our understanding about the interaction between microbes soil and plants, they also teach concepts that are less supported by main stream science, including the following.

• Soils can be regenerated very quickly
• Use of compost tea.
• Use of microscopy to identify and quantitate soil microbes.
• The importance of fungal to bacterial ratio.
• Weed control.

Should you be applying these concepts in your garden?

Soil Can be Regenerated in One Season

Under the Soil Food Web Approach it is claimed that “Only with the complete soil food web in place, can the ecological functions of the soil be restored, protecting and purifying the world’s waterways, reversing climate change and providing super-nutritious foods. Using BioComplete™ Soil Amendments, most soils can be regenerated in the first growing season.”

Such lofty claims are not uncommon. Imagine, in one growing season you can regenerate your soil, purify the world’s waterways and reverse climate change – you just have to take their course!

What is BioComplete?

The minimum requirements for bio-complete compost:
• Bacterial biomass, 135 mq / g compost
• Mushrooms biomass, 135 mq / g compost
• S: B ratio, equal to or greater than 0.3: 1
• Protozoa, 10,000 / g compost
• Useful nematodes, 100 / g compost
• Cilliates, less than 5 / drop 1: 5 solution 

I assume S:B ratio is the F:B ratio discussed below and that “mushroom” biomass is really the fungal biomass? The school normally emphasizes the importance of the right kind of bacteria, but in this case any bacteria will do.

One thing we do know about soil is that it does not change quickly. It is not regenerated in one season by adding compost, even if it is perfect compost.

Microscopy Can Identify the Microbes in Soil

A critical component of the schools teachings relies on the ability of gardeners and farmers to identify the microbes in soil, compost and compost tea. They offer a course to teach you how to do this.

A microscope can be used to identify a type of organism. A bacteria looks quite different from a fungal hyphae or a nematode. An expert might even identify some common species, but it is not possible to identify microbes past that level by simply viewing the sample under a microscope.

Consider this, scientists have not identified most microbes in soil. The current estimate is that we may know something about 20% of them, but we don’t even know the total number of species.

I have gone into more details of the limitation of a microscope in Soil Bacteria – The Myth of Identification & Management.

Here is a simple test of this concept. As a graduate of their microscopy course you should be able to do the following for the image below.

• Determine that the fungi is alive.
• Determine the mass of the fungi on a per gram of sample basis.
• Determine if the fungi is beneficial or not.

Good luck.

Is it important to identify organisms past the type stage? According to the Soil Food Web School it is important. It is critical to make sure that your soil and compost have the right organisms and that they are beneficial in nature. The approved labs doing testing for the school use the schools techniques which are claimed to distinguish between beneficial and non-beneficial bacteria and fungi. The only way to know an organism is beneficial is to identify it, which as already stated, is not possible with a microscope.

The Use of Compost Tea

I have reviewed compost tea thoroughly in other posts. It does contain nutrients and therefore helps plants grow. But the nutrient level is not higher than in the compost itself and so you might as well just use the compost.

Proponents of compost tea, including the Soil Food Web School believe that the real value of tea is in the microbes it contains. One problem with brewing tea is that you never know if the bacteria in the tea are beneficial or pathogens, so it might actually harm plants and you. That is true even for aerated tea.

As far as soil goes, the number of microbes you add with diluted tea is so small compared to the existing number in soil, that it makes almost no difference. The total number in soil does not increase after adding the tea but the biodiversity may change about 1% of the soil microbiome. However, scientists don’t know if these changes are positive or negative.

There is some experimental evidence that a spray of microbes might fight diseases but most of these studies brew specific strains of bacteria for each type of disease. The idea that a gardener can brew up an unknown batch of compost tea and suppress diseases is not supported by research.

The Importance of the F:B ratio

Dr. E. Ingham and her school consider the fungal to bacteria ratio to be critical for developing healthy soil. They claim that each plant species grows best in a specific ratio. Grasses and perennials prefer a bacterially dominant soil, while woody plants prefer a fugally dominant soil.

The first time I heard this I immediately visualized a city park. Lush grass dotted with healthy large trees. Both the trees and grass grow well and these parks are located on all kinds of soil.

Many different types of soils have been analyzed for this ratio and forests do tend to have more fungi, and grasslands have more bacteria. F:B ratio for different habitats:

• Coniferous forest: 100 to 1,000
• Deciduous forest: 5 to 100
• Weeds and Grasslands: 0.1 to 1
• Agricultural fields 0.1 to 1

Scientists agree that different soils have different ratios. It is also accepted that agricultural practices such as tilling and using synthetic fertilizer tend to favor bacterial growth. Adding organic matter increases the total microbe population. Using organic matter with a high C/N ratio favors fungal growth and low C/N ratio favors bacteria.

What science does not agree on is the idea that plants grow best in soil with a particular F:B ratio.

It is the plants that modify the soil, not the other way around. Trees produce high carbon debris, which favors the growth of fungi and therefore over time the F:B ratio increases. Replacing the trees with grasses and herbaceous plants reduces the carbon level of plant debris and bacteria are favored.

Both trees and grasses grow in a wide range of F:B ratios and we don’t know how the ratio affects plant growth. There is no current science to support the idea that plants need a special ratio. There is also no support for the notion that gardeners should modify the ratio for better plant growth.

F:B Ratios Control Weed Growth

The school promotes the idea that weeds grow best in bacterially dominated soil, so increasing the quantity of fungi will eliminate weeds.

What happens after a forest fire? The trees are gone and almost immediately the ground is covered with weeds including grasses and herbaceous plants. And yet, the soil still has a high F:B ratio. This should be a perfect situation where weeds won’t grow, according to the school.

What about weeds in a vegetable garden? The garden might have a low F:B ratio since the soil has been used for crops, making it the perfect place for weeds to grow. What if we change the F:B ratio so it is high?

According to Dr. Ingham, the weeds will die out. What about the crops? Well they would also die out. Why? Except for fruit trees and fruit bushes the other crops we grow are just weeds. Remember there is no biological difference between a weed and any other herbaceous plant. Dr. Ingham’s claim that the weeds would die out while crops would flourish makes no sense.

The idea that you can control weeds by changing the F:B ratio has no support in science.

Some Final Thoughts

Dr. Ingham and the Soil Food Web School have become popular and it is great to see them promote the development of healthy soil. Even though some of their ideas are valid, it is important to examine all of their claims more closely. The school does make claims that the ideas are “supported by science” but in reviewing their material, there are few references to studies that support their claims.

Main stream science does not support the the topics discussed above. If you disagree, provide references to published science in the comments below.