Degraded soil can be avoided and improved naturally
Published on: August 25, 2019
‘It’s time we stopped treating soil like dirt’ – was the title of a report of the Guardian issued on July 11th, 2019. The related video was simply called: ‘Not another climate horror story’. Another article argued that we are currently loosing thirty football fields of soil every second. Further, ‘a third of the world’s soils are already degraded’ while, under current rates, all topsoils of the world would be degraded in only 60 years. What is so terrible about the way we treat our soils? And, how can that be changed?
Soil degradation – if you are at least remotely interested in growing plants, this is probably a term that you have already stumbled upon. In line with fancy words like land degradation, soil erosion, or desertification, soil degradation is commonly used to describe problems that negatively affect agricultural productivity. But what does it mean exactly? Why is it so bad? What causes it? And, most importantly, what can we do against it?
Here are some answers about one of agriculture’s biggest archenemies and a major threat to global food security. Turns out, we can not only prevent soil degradation beforehand but also reverse it once it has already occurred. And we can do that at the hand of natural means!
Soil is a cocktail of different ingredients.
To understand soil degradation, we have to dig a little deeper into what soil consists of. In fact, instead of being a one-ingredient drink ‘on the rocks’, it is actually a cocktail of different components.
Simply speaking, soil contains four different materials. The proportions of which may vary within different soil types:
- Inorganic mineral particles: These are small particles of different sizes like sand or clay that initially stem from rock material (the so-called ‘parent material’). They usually comprise more than fifty percent of the soil’s volume.
- Soil Organic Matter (SOM): This either consists of living organisms such as bacteria, earthworms, fungi, or non-visible microorganisms or dead materials from plants and animals. Mostly, soils contain between 2 – 10% organic matter. A teaspoon of topsoil typically contains a vast range of different species and up to 6 billion (!) microorganisms.
- The final two components are Air and Water which are stored in the free spaces in-between organic and inorganic materials. Together they come up for up to half of the soil’s volume.
Good soil ensures our wellbeing and survival.
For us, the soil’s most obvious function is being the cradle for the food we eat. Thus, simply speaking, we call it ‘good’ when it nurtures our crops well. All of the aforementioned components play a role in that.
For example, you can imagine that the soil of a desert has a relatively small share of water. Surprisingly though, it still contains a lot of living organisms such as mosses, algae, and microorganisms. These are ‘sleeping’ in the sand waiting for the next rainfalls to come. And when they do, they reveal this life in the form of a flourishing fauna covering the sandy desert soils for as long as there is enough water. This exemplifies the importance of the three so-called ‘essential nutrients’: hydrogen, oxygen, and carbon (primarily in the form of water and air). In this example, water is the one ingredient that hinders the plant’s growth – also called the ‘limiting factor’.
However, not only the essential nutrients can be limiting factors. Most plants need more than just air and water. Within the above-mentioned components, soils also contain minerals that plants need to grow, flourish, and produce food. 17 minerals comprise the most essential ones. For instance, you might have heard of nitrogen, phosphorus, or potassium as being important. In conventional agriculture, these are often added to the soil in the form of synthetic fertilizers to give crops a direct artificial boost.
Plants need organic helpers to thrive.
In nature, plants cannot access these minerals on their own as they are ‘chained up’ in physical and chemical connections within the soil components. Plants are not able to break these, and that is where it becomes interesting. They need the help of living organisms such as bacteria, which are natural liberators.
Bacteria and microorganisms are able to ‘unchain’ the minerals and make them available for the plant’s root systems. In return, they obtain valuable sugar making this relationship a win-win situation – also called ‘symbiosis’. This sugar is actually carbon which is taken from the atmosphere through photosynthesis and then stored in the ground – quite a nice co-benefit.
Mycorrhizal fungi: Why plants love an athlete’s foot
Another soil inhabitant worth mentioning is ‘mycorrhizal fungi’. What sounds like a horrible disease is actually our most valuable underground nutrient retailer. In a healthy soil, these fungi create a sort of subway system (the mycorrhiza) that connects fungi and often multiple plants.
Through these organic channels, they communicate and distribute minerals within the soil. Mycorrhizal fungi also protect plants from diseases. Watch this video about these networks and you will never want to cut a tree again.
Healthy soil as a water absorbing sponge
These connections are part of greater systems called ‘nutrient cycles’ which are essential for life on this planet. However, living organisms in the soil do not only provide nutrients. They also improve the soil structure. Earthworms, for instance, dig through the soil leaving behind tunnel systems for water to infiltrate into it and stay.
This way, rainwater enters the soil instead of running off the surface of compacted ground. It then becomes available for plant roots and does not leach away while taking important nutrients with it. Think of healthy soil as a natural sponge that can hold water for a very long time.
So, fungi, bacteria, and their fellow creepy-crawlies are essential for healthy soil. However, they need something to eat. They feed on dead and decaying organic matter while turning it into humus (nope, this is no Middle-Eastern dip). Think about leaves, branches, mulch, or animal dung in and on the surface layers of the soil. These materials also increase its capacity of storing carbon and prevent it from drying out. All this organic matter – the living and the dead – makes up most of the topsoil which is why it is so valuable for plant growth.
The pH value: A determinant for plant growth
Another important aspect of happy soil is its pH value – don’t worry, I will keep it simple. The pH indicates if the soil is acidic or alkaline – you may call it sour or not-sour – on a scale from 0 to 14. If it’s below 7, it is acidic. If it’s higher, it is alkaline soil.
So, what does that mean? The pH value affects chemical processes within the soil and thereby determines to what extent nutrients are available for plants. For example, phosphorus becomes inaccessible for plants in soil with a low pH (acidic) as it forms a strong connection with aluminum. This problem is related to the fact that helpful microorganisms do not like to mingle in acidic soils. Therefore, they are not available to support the plants.
The pH affects nutrient availability.
Imagine your plants as an outdoor adventure park. If the weather (the pH value) is too hot (acidic) or cold (alkaline) your valuable customers (the nutrients) will just stay at home enjoying the comfort of their houses (chemical and physical connections). The result is your park running low until it finally bankrupts.
That is why farmers would always want to have a close look at the pH value of their soil before cultivating crops. Good soil generally has a pH between 5.5 and 7 and is, therefore, neutral or only slightly acidic. This is because most plants, as well as helpful microorganisms, prefer those balanced conditions. However, others have specialized in more extreme values. Those are often pioneer species which we will get to later.
We are destroying our own fundament.
The Food and Agriculture Organization of the United Nations (FAO) defines soil degradation as ‘a change in the soil health status resulting in a diminished capacity of the ecosystem to provide goods and services for its beneficiaries.’ Simply put, when soil degrades, it loses the ability to support life on this planet. These goods and services comprise, among others, the support of our food crops, plants, and trees, carbon storage and also the filtering of water. They are essential for our wellbeing and survival.
Erosion: Loosing the topsoil
Soil can degrade as a result of different causes that may be related, among others, to its fertility, the amount of organic matter in it, or its structure. For example, water or wind erosion are drivers of soil degradation. They occur when bare soil is exposed to the weather by cutting down plants or trees that used to cover and protect it. Heavy winds and rainfalls may then take away the surface layers of the soil – the topsoil – and blow or flush it elsewhere. Much of that valuable organic matter which primarily lies in the topsoil can get lost that way.
Controversially, soil degradation is often directly linked to human activities. We are currently responsible for destroying the very resource we need for our survival and well-being. Think industrial activities, the expansion of cities, and, most importantly: Conventional agriculture.
Soil degradation through monoculture farming
Conventional agriculture is mainly done in long-term intensive monocultures – imagine a farm plot with only one crop. It is not hard to imagine how that may damage the soil. A specific plant needs specific nutrients. Another plant of the same type will, of course, need the exact same ones. When the same piece of land is cultivated with the same type of crop for a long time and without breaks, the relevant nutrients become depleted. Then, they have to be added manually. In conventional agriculture that means: Synthetic fertilizer .
Killing instead of nurturing
Synthetic fertilizer has a lot of downsides. Most importantly, it harms the living organisms in the soil, and it leads to increased growth of unwanted weeds. As these are seen as harmful for the crops – they compete for the same nutrients – they will be killed by chemical herbicides. Again, those have negative impacts on the soil.
Many of these herbicides are chelates and bind important metals. Plants, however, need those to fight off diseases and cannot access them anymore. Now, farmers need to spray fungicides which – guess what? – damage the soil, AGAIN. They kill the beneficial living organisms. As you see, we end up in a downward spiral in which the soil becomes less and less capable of supporting our plants itself. Watch this great video if you want to learn more about it.
When soil gets sour: Acidification
As we have seen earlier, extremely acid or alkaline soils are not great for food production. Many important crops can hardly grow in those conditions. Especially, acidic soils are often caused by human practices. Soils acidify naturally but that process is very slow. Again, the culprit is conventional agriculture speeding it up, the very creator of most of our food.
Agriculture drives acidification in two different ways. The first one is synthetic fertilizer. Nitrogen, for example, is one of the most important nutrients for crops and is often added in fertilizers make soils more acidic. First and foremost, that is ammonium-based fertilizers made from gas which have the worst impact.
The second one is the removal of produced plants from the soil which interrupts the nutrient cycle. Plant materials are usually slightly alkaline. In nature, when the plants die, they naturally decompose which returns that alkalinity to the soil and, therefore, balances out soil acidity. In agriculture, these alkaline materials are being taken away through harvesting and grazing animals and are often not returned to the soil. In the long run, it then becomes acidic.
Tillage: Tearing the soil apart
Another important example of how we literally damage our soils is the practice of tillage. In conventional agriculture, farmers agitate the soil after the last harvest to prepare their plot for planting new seeds every year. You have probably seen your local farmer plowing his fields with a tractor like this:
While this may look like a good idea (does it even?), tillage is actually harming the soil in many ways. For instance, it destroys its structure and decreases its ability to infiltrate and hold water. All the good work that our drilling and digging organic helpers have done is thereby destroyed in a split second.
So-called ‘soil aggregates’ – lumps of soil with pores in between them – usually form the structure of good soil and need years to develop. Tillage crushes them like a nutcracker. Also, it reduces the amount of soil organic matter and leads to a loss of important nutrients. In short, it does more bad than good.
Nurturing soil biology to avoid soil degradation
We have now seen how today’s common agricultural practices are responsible for the ‘loss’ of healthy soils. While this topic could fill entire books, it is way more encouraging to look at solutions rather than the problems. So, how can we avoid soil degradation?
The answers lie in nature itself. As we have seen earlier, it is essential to have a great number and diversity of fungi, bacteria, and microorganisms in your soil to keep it healthy. These are our best helpers in creating conditions that are best for food production, carbon storage, water infiltration and all the other services that we demand from our soils. To prevent our soil from degrading we need to make it a comfortable abode for these little fellows. So, how do we keep them where we want them?
As providing free WIFI, coffee, and a book exchange is unlikely to succeed, we need to think of something better. Luckily, there is a multitude of practices that have proven to be more inviting. Here are three basic principles that you can follow to become a better host.
1. Keep soil disturbance minimal.
This is quite simple: Do not destroy what you need. Tillage is only one example of how the soil structure can be damaged. Another one is called compaction which describes the process of heavy machinery such as tractors driving on the soil. By doing that they ‘compact’ the soil, whilst destroying its structure.
Imagine a root trying to find its way through the soil to reach valuable nutrients. It may either face loose material full of little tunnels and fissures or a wall of pressed earth representing an insurmountable barrier. Keeping heavy machinery use and tillage at a minimum is, therefore, key for maintaining healthy soil.
2. Maintain organic ground cover
If you want to maintain a healthy population of creepy-crawlies in your soil you need to give them something to feed on. This is best done by keeping the ground covered with dead or living plant materials, leaves, mulch, or/and animal manure. Our organic helpers will then decompose those materials while turning them into nutrient-rich humus for plants to uptake. Thereby, they thrive and mingle in the soil in enormous numbers which helps to maintain a good soil structure.
Soil cover has another advantage. Especially in drier climates, it helps to keep water in the soil that would otherwise evaporate into the air. Through this organic ‘lid’ on the top, it stays available for plants for a longer period.
3. Diversify plants
The more plant diversity you have, the more fertile and resilient becomes your soil. Logically, different crops need different nutrients which prevents single nutrients from running out. In agriculture, there are two simple approaches to obtain higher diversity: crop rotation – growing different crops on the same piece of land over different seasons – and intercropping – cultivating multiple crops at the same time. Both have positive impacts on the soil.
Agroforestry: Working with diversity and perennials
There are a lot of other options for increasing the diversity of your plot. Agroforestry, for example, goes beyond that by creating a system of abundance that every soil would be thankful for. Its plant diversity is usually higher than that of most conventional systems.
It usually works with perennial plants – trees and plants that have to be replanted every (or every second) year – which leaves even more nutrients in the ground, prevents acidification, and creates a great network in the soil.
Restoring degraded soil by natural means
Preventing soil from degradation before it has occurred is a pretty straight-forward and relatively simple procedure. The solutions are already there and do not seem too difficult to apply – depending on your individual situation of course.
But what if the soil is already degraded? What if it has been mismanaged for years with hardly any topsoil left and a structure that compares to a block of concrete? Is there a way to reanimate our earthy patient, once it has already ‘died’?
Ecological succession: Natural soil restoration
In nature, when there is a disturbance – say a wildfire or storm – destroying the ecosystem, it will restore itself. This happens through a process called ecological succession.
Typically, there are specialized, smaller species that come first, create more favorable conditions for other bigger ones who then follow, and prepare the ground for even bigger plants. This goes on until the final stage – the climax community – is reached. In Central Europe, for example, that would be a forest.
Pioneer species preparing the soil
The first plants to return are pioneer species that are specialized to settle and survive in very harsh conditions. Once these front-runners are established, they prepare the soil for others through the magic of photosynthesis. They take up sunlight and turn it into sugars that attract living organisms.
These will slowly become more abundant making more and more nutrients accessible for plants. The pioneers also provide shade and protection from the wind which helps more sensitive plants to grow.
Therefore, a major part of ecological succession is happening in the soil. More organic matter is added, and important organisms (re-)establish themselves.
The reformation of the topsoil
Slowly but steady, the place will become more livable for other plants as well. Once these runner-ups grow bigger, they ungratefully outcompete the pioneers. Those die and become natural fertilizers themselves, again, supporting the reformation of the topsoil.
The dead material ends up on the soil and the living organisms return to feed on it, decompose it, and turn it into nutrients. This process repeats itself multiple times while the ecosystem grows bigger, more complex and more diverse. Though, it may take decades or even millions of years (after a mass-extinction) until the climax community is reestablished.
Manually accelerating the succession
When you are relying on your soil for food production, you probably won’t have a couple of decades and certainly not millions of years. You’ll have to find ways to speed up this succession and create soil that supports your plants.
The obvious solution is going to your local farm supply store. You could buy loads of synthetic nitrogen, potassium, and phosphate fertilizers and drench your soil in it. This won’t restore your soil at all, but it might keep your plants alive for a short while.
However, this has several downsides. It is very expensive, and you would have to repeat the process regularly. Further, it may kill the very last helpful organisms in your soil, lead to acidification, and maintain a lousy soil structure. So, in the end, you will be paying a lot of money and still yield disappointing amounts.
Organic materials to return soil life.
A much better solution is to use organic materials to work with – instead of against – ecological succession and, thereby, accelerate it. The key is to restore fertile topsoil with loads of organic materials and organisms as fast as possible. Often, the soil still contains minerals, but the plants cannot access them, because the soil biology is missing.
Many natural materials can help to bring back life into the soil. Here are some of the most useful ones, all of which increase organic matter in the soil. They are much less soluble than synthetic fertilizers which means that they do not leach through the soil easily:
- Lime: Lime is made from pulverized limestone or chalk. It helps to increase the pH value of your soil making it less acidic. Plants can access nutrients better through liming.
- Land plaster: Also called ‘gypsum’, land plaster is a ground rock material. It improves soil structure, creates a neutral pH, and supports soil organic matter
- Rock dust: Another ground rock material containing great amounts of minerals that might have been lost through erosion, leaching, or intensive farming.
- Compost: You have probably heard about this one. It is decomposed organic material – could be your kitchen waste – that is spread on the soil to create valuable topsoil and add nutrients.
- Mulch: Mulch can be used as ground cover material. This could be barks, straw, leaf materials, or sawdust to keep the soil moist, prevent erosion and feed life in the soil.
A natural short-cut to healthy soil
Especially rock dust, lime, and land plaster decrease acidity in the soil, increase the availability of nutrients for plants and also suppress toxic elements. This helps earlier plants to establish and kick-start the ecological succession. It is important to note that these amendments are only a short-cut, but no long-term solution.
The focus should always lie on triggering a thriving soil biology. Maximum plant diversification, constant ground cover, minimum soil disturbance, and the use of perennial plants will help and accelerate the return of soil biology. Thereby, healthy soil will be reestablished.
Soil degradation can be prevented and amended.
We have now seen that soil is more than just sticks and stones. We have seen that it is one of our most important resources that is not only responsible for growing our food, but also fighting climate change, and filtering our water. In fact, healthy soil is of major importance for our well-being and all life on earth.
Unfortunately, we have also seen that we are currently not treating it well. Especially conventional agriculture that should know best is now the major cause for our soils to suffer. The use of synthetic fertilizers, tillage, and monoculture farming are driving their depletion and destruction.
Luckily, there are solutions and they are ready to be used. Principles such as the diversification of plants, ground cover, no soil disturbance, and – most importantly – working with nature instead of against it, have proven to help tremendously. It is understood that a flourishing life in the soil is key and we know how to keep AND bring it there. Let ‘A Bug’s Life’ begin!
Agroforestry is a land-use management system that has all these principles at its core. It has proven to be outstandingly beneficial for creating and maintaining healthy soil and with it flourishing and productive systems for people and nature. We from reNature drive and support the spread of agroforestry systems globally. Please check out our website and use this link to support our cause.