Soil Building – How to Make Deep Rich Soils by Imitating Nature

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Soil building is one of the most important aspects of regenerative land stewardship.

If you are into permaculture or regenerative agriculture, you’ll know that everything revolves around healthy soil. Soil rich in nutrients, organic matter, and beneficial microorganisms supports healthy plant growth, which, in turn, supports a thriving ecosystem.

In short, everything starts with healthy soil.

In this post, I’ll try to demystify the process of soil building the permaculture way entails and how you can apply it on your land.

This topic is very close to my heart because when I started with my property, I was disappointed to find out that my soil was shallow, compacted, alkaline, and sometimes waterlogged for months. I had ambitious goals for annual gardens, food forests, and perennial grasslands.

After delving deeper into the topic, I realized that my only two options are importing good soil (not feasible) or improving the soil I already have. The latter offers me the chance to regenerate the soil and learn more about soil biology, so I’ve embraced the soil-building challenge head-on.

In my research, I discovered something fascinating: there are more microorganisms in a teaspoonful of healthy soil than there are people in the world. And when we add in earthworms, nematodes, and other soil life, we can see that there is much more to soil than we realize looking down from above.

We in permaculture should try to replicate this kind of biological richness in our food-growing systems. But what I’ve learned is that emulating a grassland is different than emulating a forest, and for this reason, you first have to be clear on which ecosystem you’re trying to copy. Here is why.

Ecological succession as a model for improving the soil

Ecological succession is a process of change in the species’ structure over time. The established species influence the soil composition and alter it over time.

As you can see from my sketches above, there is a significant difference in soil found in the bare field than in the forest.

The weight of fungi in forest soils is much greater than that of bacteria. In grasslands, however, there is an equal distribution of the two. In agricultural soils that are routinely tilled, in contrast, the weight of fungi is less than that of bacteria.

But how does this apply to me, you may ask? 

Suppose you are trying to create a healthy pasture, a self-fertilizing food forest, or even just a productive annual garden. In that case, you must simulate the conditions where the intended plants are found initially.

So, let’s look at the three most common situations you’ll face on your farm: annual gardens, grasslands, and food forests, and see what steps you can take to bring your soil to life.

How to Make Rich Soil Scenario 1: Annual Gardens/Market Gardens

Annual plants colonize bare soil following a disturbance. As they wither and die at the end of their growing season, their remains fall on the ground and act as mulch that bacteria and earthworms feed upon.

This cycle repeats itself annually, with organic matter building and creating humus. Here is what to do in your soil building efforts to replicate these conditions.

• Don’t disturb the subsoil and encourage biological tillage

As seen in nature, to establish annuals, you have to intervene mechanically to prepare beds for crop planting and establishment. However, you don’t want to till deep as you don’t want to disturb the soil structure.

The undisturbed subsoil lets earthworms dig their tunnels and provides aeration and drainage while their excretions bind together soil crumbs. They are essential in healthy soil structure and replace mechanical with biological tillage.

If you don’t compromise earthworms, microbes, and other soil organisms through soil inversion, they can perform much of the tillage needed to create and maintain loose, fertile soils.

However, suppose your soils are biologically dead. In that case, those microbes have to come from somewhere. That is why we sometimes need to feed the soil with biologically-active decomposed organic matter rich in beneficial microbes – the compost.

• Bring your soil to life with compost

Good compost supplies both the organic matter for soil building and the fertilizer for the crops; most importantly, it’s packed with soil organisms that trigger biological activity. It inoculates your soil with microbes that will digest nutrients present in the soil and feed your plants.

Compost is the key ingredient for building and maintaining healthy soil. Because of its unique characteristics, compost cannot simply be replaced with manure, natural fertilizers, or green manure. If you’ve just moved to a new garden and want productivity, compost will rapidly make your soils fertile.

• Maintain organic matter with mulch

Once you have your soil biology working for you, you need to feed it so it can feed your plants. There are several ways to maintain soil organic matter in your annual garden, and one of the easiest is using lawn grass clippings, leaves, straw or cover crops, and, of course, compost.

The mulch is then left on the surface to decompose. Adding this layer of organic matter and spreading it is, in effect, ‘composting in place’, where the garden beds become large composting areas. 

Then by the actions of earthworms, bacteria, fungi, and insects, the organic matter is slowly broken down and released into the soil, providing nutrients to the garden.

While all this sounds great, if you are running a market garden operation, this practice is restrictive and somewhat impractical. Here is what JM Fortier in his book The Market Gardener has to say: “Based on my experience, direct seeding into crop residues, mulch, or crimped down cover crops is not straightforward, causing unpredictable germination rates – a nightmare for any commercial grower.” Something we should bear in mind.

• Use crop rotation to mimic diversity

With crop rotation, you can mimic the diversity of annual plants growing on a bare field. Differing root systems among plants penetrate the soil to different depths, improving its structure.

By ensuring crop diversity and alternating crops, you allow the soil to keep producing without being drained of its nutrients while eliminating a number of diseases and harmful insects that often occur when one species is continuously cropped.

How to Make Rich Soil Scenario 2: Grasslands – Pasture/Cropland

As we move in succession, the perennial grasses are slowly taking over.

Big herbivores are roaming in herds feeding off these grasses, trampling them down, and fertilizing the soils. Over long periods of time, organic matter builds up, and now we have fungi and mycelium with bacteria equally represented.

Here’s what your soil building efforts should involve.

• Don’t disturb the soil – ensure the lowest level of mechanical disturbance possible

Unless you need to repair the compacted soil, poor drainage, or do some initial tillage to sow the perennial cover, you should aim for no till, no compaction, and the lowest possible mechanical disturbance.

Make your tillage minimal!

Here the goal is the same as with an annual garden, enabling the biological tillage but also taking advantage of the mycorrhizal fungi, which form symbiotic relationships with the roots, extending the plant’s root network. 

They also prevent pathogens and improve water use efficiency and absorption of other nutrients. 

• Always keep your soil covered with perennial cover crops

If we look at perennial native ranges, we can see they are permanently covered. 

So the first step to rebuilding soil structure and health of grassland is to get it under perennial cover, which then acts like armor for the soil. 

Bare soil is detrimental to its health, and you only find bare soil in catastrophic events or where humans have imposed their will upon it.

Cover crops are planted specifically to build and hold soil and to smother weeds. They range from long-growing perennials to short-term green manures, but the aim is the same: a solid cover of plants. Their leaves will protect the soil from hammering rains, and eventually, their residue carpets the surface with nutritious, humus-building matter. 

• Plant diverse perennial cover crops

Once again, if you look at native perennial ecosystems, we can see diversity. 

Rather than resorting to one or two species of cover crops, they should be seeded as multi-species combinations, through doing so, you are mimicking what nature does. 

You optimize solar energy collection as different plants have differently shaped leaves. Because the roots penetrate varying depths, the mycorrhizal fungi can deliver moisture and nutrients from the other areas of the soil profile.

You can design your cover crops to address your specific concerns:

• Protecting the soil as living mulches
• Adding organic matter as green manure
• Boosting fertility with N fixing legumes
• Dealing with compaction

Even if you are using your grassland to grow cash crops, you can maximize your profits by mixing cover crops. Cover crops can be sown before, with, or after the cash crop, so you always have something growing.

• Planned disturbance in a form of animal impact and planned grazing

In nature, soils are formed in conjunction with herbivores. In this case, through large herds of herbivores moving across the planes, but also by other local wildlife; rabbits, grasshoppers, and other insects. All of them are taking this forage, the biomass, and endlessly recycling it.

Animals are an integral part of a healthy ecosystem. But how can they help you to build healthy soil?

A prime example of building soil with big herbivores is the holistic planned grazing practice conducted by Allan Savory and others like Greg Judy. They use high-density animal herds that graze a paddock for one day before being moved to the next paddock. Joel Salatin has a similar technique and a grazing plan with a high-density herd impact and ample recovery time.

The goal is for animals to consume a third of the grass in the paddock and trample the rest into the soil to feed earthworms and soil microbes, thus replicating the natural herds of large grazers coevolved with grasses.

How to Make Rich Soil Scenario 3: Food Forests/Permaculture Orchards

With time almost every ecosystem will eventually end up forest-like.

In a forest, organic matter in the form of fallen leaves, twigs and branches, and dying plants are all deposited on the forest floor, where they are decomposed into rich humus by the action of fungi and other organisms.

Fungal fabrics, the mycelium, run through the top few inches and act as interfaces between plant roots and nutrients, bringing distant nutrients and moisture to the host plant and extending the absorption zone well beyond the root structure.

No tree could reach maturity without this symbiotic relationship.

Food forests are actually younger versions of mature forests. In his book Creating Forest Gardens, Martin Crawford explains- “A food forest is a forest modeled on the structure of young natural woodland, and it often contains nitrogen-fixing trees and shrubs, which are pioneer species, establishing quickly and improving soil and environmental conditions for other trees to follow.”

If you are starting from scratch, let’s see what soil building activities you should focus on to transform a bare land into a food forest.

• Improve your soil with green manures and transitional ground-covers

Preparing the soil before planting offers certain advantages. A year of cover cropping and woody mulching offers a chance to build organic matter, correct fertility imbalances, and, most importantly, accelerate fungal dominance.

Fruit trees generally prefer high-quality soil, so it is vital to achieve a good layer of humus and try to use as much biomass as possible on the soil.

Following the initial tillage or sheet mulching, existing grasses will generally be ready for cover crops, preferably red or crimson clover, as these two nitrogen-fixing legumes have a stronger affinity for mycorrhizal fungi.

Other Legumes and dynamic accumulator plants are also acceptable, and these can even be oversown into existing grasses.

• Inoculate your soil with mycorrhizal fungi  

Food Forest soils ideally contain a fungal presence ten times higher than bacteria. If you’re starting with a bare field with no fungi present, you can encourage mycorrhizal associations through inoculation with fungi. Here is what Michael Crawford recommends in his book Creating Forest Gardens:

• Dip exposed roots of seedlings into water enriched with the spore mass of one or more mycorrhizal species. 
•  Broadcast spores onto the root zones of existing trees and shrubs using spores in a water carrier.
• Place a little soil from the root zone of proven mushroom-producing trees around seedlings in the nursery or soon after planting.
•  Inoculate the compost of pot-grown plants with a mixture of dried spores from suitable species.
•   When planting trees or shrubs, scatter a dry spore mixture into the planting hole.
•   Use woody mulch to feed the fungi.

Compost, deciduous wood chips, and other woody material can be added on top of the green manure crops. The woody material is what drives the fungal dominance you want for a healthy food forest. 

The goal, plain and simple, is to create what Michael Phillips in Holistic Orchard calls fungal duff – the litter layer where mineralization and humification take place through the action of fungi.

Mulching with wood chips and chopping and dropping woody plant material on the ground helps mycorrhizae thrive. This fungal connection provides the balanced nutrition necessary for a tree to better withstand disease.

• Create self-sustaining fertility with nitrogen fixing trees and dynamic accumulator plants

The self-fertilizing nature of the food forest comes from using nitrogen-fixing plants and other plants like comfrey that are particularly good at raising nutrients from the subsoil. Through their use, efficient nutrient cycling develops in a forest-like system, maximizing fertility for other plants to grow.

Nitrogen fixers are extremely useful fertility providers in a food forest. Techniques like ‘chop and drop’ mulches, coppicing, and pollarding from these plants, in particular, can release the nutrients they have extracted over time from the earth or air. ‘

Simply having them shed leaves on the ground can improve fertility. There are many nitrogen-fixing plants at each level of the food forest, and I recommend reading Martin Crawford’s book for a comprehensive list.

Take Action! (Get your free Soil Building Checklist)

With each scenario outlined above, you strive for the highest percentage of organic matter in your soil and provide habitats for a high diversity of soil food web organisms. 

In an annual garden, this would be geared toward bacteria, and in a forest garden, more toward mycorrhizal fungi. 

The easiest way to know your plants’ needs is to ask yourself: “Where did the plant grow natively, Field or Forest?

Depending on the type of system you wish to achieve, bring animals into the system in any way you can. They help with organic matter and nutrient cycling: earthworms, herbivores, and poultry all are integral to system health.

And always remember nature is our greatest teacher. Working in harmony with nature is always the best way to proceed, so whatever you plan to do, ask yourself: “What would nature do? How would this system I’m trying to set up look naturally? And then adapt it to your circumstances.

Hope this helps in your endeavors. Let me know what you think in the comments!