Soil, Water and Life

Think like a root: how to make healthy soil

Over the ages, plants have evolved to thrive without fertiliser, pesticides or having their root zones ploughed up. Instead, they have developed together in a healthy symbiosis with micro-organisms in the soil, where each helps the other thrive.

Feed the soil, not the plants

How do plants feed themselves and grow?

Schoolchildren learn about photosynthesis, where the plant takes water in through the roots and takes in carbon dioxide from the air via the leaves, then uses energy from sunlight to split those molecules apart and recombine them in a chemical reaction to create sugars and oxygen.

The energy-rich and carbon-rich sugar is used to build the plant structures, but large amounts is also sent down to the roots where it is secreted into the soil in "exudates" - sugar-rich mixtures of proteins, carbohydrates and other chemicals that the plant releases, and which nourish the microorganisms in the soil that are beneficial to it -- and also minimise the harmful ones. These “good” organisms can form a powerful protective and nourishing layer around the root: each plant secretes its own preferred mix.

The soil (and surface) contain a massive diversity of lifeforms: bacteria, fungi, worms and nematodes, and insects and other arthropods. These organisms eat plants when they die and fall to the ground, returning their nutrients to the soil. But the story does not end there.

The highest concentrations of these helpful micro-organisms are found closest to the plant roots, because that is where they find the rich plant exudates that they favour.

These micro-organisms protect the roots: but they also deliver nutrients to them. Bacteria and fungi feed not only on the plant exudates or dead plant matter: they also feed on the minerals derived from the ‘weathering’ of rocks or sand grains, taking in chemicals such as nitrogen, phosphorus or potassium, which plants need. Fungi build networks of filaments through the soil, helping build a healthy porous soil structure, through which air, water and nutrients can pass.

Protozoa eat the bacteria and release most of those nutrients into the soil in the root zone (again, because that’s where the exudates and thus most of the right bacteria are.) The fungi get eaten by micro-arthropods and nematodes, which in turn get eaten by bigger creatures, which get eaten by spiders, voles, birds, and so on. A healthy system like this can maintain a dynamic balance, which tends to self-regulate (so if one component gets too dominant, for instance, its predators may rise to eat it back down to size).

We have found this presentation by soil scientist Elaine Ingham very helpful (founder of the Soil Food Web School)

If your plant roots are surrounded by the right micro-organisms, and get enough water, then you usually won’t need artificial fertiliser: the bugs will provide all the plants need.

So we like to say that it is important to feed the soils, rather than just the plants.

Healthy soils and climate change

All living creatures are substantially made of carbon. So converting to healthy productive agriculture like the practices advocated by Tiyeni tackles climate change directly because healthy plants take large amounts of carbon dioxide out of the air, convert it into carbon-based sugars, then push deep carbon-rich roots and exudates into the soil, in far greater quantities than with traditional methods of farming in Malawi. (And by increasing yields, we also help farmers cope with the effects of climate change.)

Researchers continue to find new miracles of organic life in the soils: for example the discovery in 1996 of “Glomalin”, a substance created by fungi which helps give healthy soil its porous structure, helps transport nutrients and water, and overall is believed to store a quarter of the world’s carbon. (Click here for more.)

What can go wrong?

All the needed nutrients are there in the soil, and if the organic carbon-rich system is healthy the plants deliver the nutrients to the plants and the plants create their own protective shields around their roots by feeding the right bacteria and fungi there.

Ploughing a field tends to have the effect of taking the micro-organisms away from where they were happiest, and putting them somewhere they don’t want to be, like on the surface in the sunshine. Ploughing can destroy the healthy soil structure built up by the plant roots, the fungus, the bacteria and so on.

And if farmers add artificial chemicals, such as herbicides or pesticides or manufactured fertiliser, the dynamic balance of the soil is thrown out of kilter in different ways. Creatures that were delivering nutrients effectively to the plants may be killed, and the protective layers around the roots may fail. So a need is felt for more pesticides or fertiliser next time, to replace the nutrients or to kill the bugs, in a harmful cycle.

In many parts of Malawi, traditional practices also encourage farmers to burn dry maize stalks and other crop residues after the harvest, releasing large amounts of carbon dioxide into the atmosphere instead of letting it move down into the soil as organic matter. Tiyeni is having great success stopping this.

And although many Malawian farmers are too poor to buy pesticides or fertiliser, they do face another fundamental problem: soil compaction. Solving this problem, at almost no cost, is probably the biggest key to to Tiyeni’s success.

Soil compaction.

Soil compaction is usually the result of often decades of human and animal footfall, and sometimes machinery. It may be invisible under the soil surface, often quite deep, so it tends to get ignored.

To understand what happens when soil is compacted, consider how a building is demolished.

The important action in any residential building happens in the spaces – the hallways, bedrooms, kitchens, living rooms, stairwells, pipes and lifts. But when that building is demolished these useful spaces collapse and the building becomes useless for life – even though the bricks, metal and concrete are still there.

A similar thing happens to soil when it becomes compacted. The spaces between soil particles of different sizes and composition are essential for the healthy ecosystems of microbes and fungi and other living things to let air, water, nutrients and themselves to percolate readily up, down and sideways in continuing renewal and replenishment.

But when soil is compacted these essential healthy spaces shrink or disappear, often with destabilising effects on the health of that soil and its ability to sustain life.

When air cannot penetrate effectively, you get more anaerobic (meaning ‘without air’) respiration, which encourages anaerobic bacteria and other harmfulcreatures to proliferate.

The reduction in spaces between soil particles also means there is less space to store water.

Soil compaction causes other problems. Roots cannot physically penetrate through this hard layer, growing sideways instead of downwards, leading to stunted plants.

Compacted soils create a further problem when the water surfaces between soil particles become more tightly curved, and the forces between water molecules (the same forces that create surface tension visible on a glass of water) make the water much “stickier”, less able to move through the soil, whether coming in from rainfall or being released to plant roots or to microbes. This difficulty in getting water into the roots makes plants wilt.

Since rainwater cannot percolate easily down into the soil it instead runs off the surface, often carrying healthy topsoil away with it and causing devastating soil erosion.

Tiyeni knows from experience that large areas of Malawi (and beyond) suffer from compacted soil, so we insist that before any healthy agricultural activities can be undertaken, this hardpan must first be broken up.

We generally advocate digging down to at least 30 centimetres. Researchers in the United States have produced these “knee” diagrams to show where, in fields they have studied, the compaction is greatest.

Source: PennState Extension

The soil in this study was most compacted around 10-11 inches or nearly 30cm below the surface: quite deep. If soils are not decompacted to sufficient depth, to at least below the “knee” in these diagrams, which is the point of highest soil density, it is leaving the hardest layers intact.

How do we tackle this and create the healthy soils?

For smallholder farmers in Malawi we advocate using low-cost but heavy-duty pickaxes or hoes, and to dig down to at least 30cm in the dry season. It is back-breaking work, as these images suggest.

You can see the hardpan on the left in both photos (imagine being a plant root, faced with the prospect of getting through that. Think like a root!)

We have seen again and again how this simple (if labour-intensive) first step can unlock the healthy potential of the soils and help create the dramatic, immediate increases in yields that creates an excited buzz in farming communities and encourages others.

Once the barrier has been broken, it is essential to then preserve and nurture the structure of the soil, to allow a healthy, sustainable and well-structured living ecosystem to develop. This can boost yields further after the initial breakup of the hard pan.

So Tiyeni’s deep beds are designed to be permanent growing zones which can be accessed from the side but which never need to be trodden on again, with closed-end contour furrows between them to hold rain water and let it percolate downwards and into the adjacent beds.

Dead plant residues are laid on top of the soils, instead of being burned, allowing nutrients to return to the soil, keeping the soils cool by protecting them from harsh African sunlight, and protecting against rain damage.

This way the healthy soils and plants can develop together, without violent disruption.

The potential for changing entire water drainage systems.

Many people know the story about how the reintroduction of wolves to Yellowstone Park in the United States changed the course of rivers there. The wolves reduced the populations of elk, which in turn allowed vegetation to flourish, reducing erosion (and increasing the population of beavers, which built dams.) Read more about that here.

We see similar potential with Deep Bed Farming (DBF). Our research page highlights the spectacular increases we have seen in crop yields and incomes for thousands of farmers and communities that have adopted it. But there are other, less evident benefits. DBF captures and stores large amounts of water underground instead of letting it run off and causing soil erosion.

This does not only create better crops and fields more resilient to drought and climate change: it also inevitably improves local water tables below the surface, and in areas where Deep Bed Farming is widely practiced it is likely to change the nature of water movements, gulleys, valleys, rivers and lakes, in particular making rivers flow less violently in the rains, and for longer periods during the dry seasons. This has been measured in Brazil, and we encourage its measurement in Malawi.

Summary: Why Tiyeni’s approach works

Tiyeni helps farmers practice Deep Bed Farming (DBF), and the rest of this website shows how it works, and outlines the spectacular results when farmers convert to this method. The advantages of converting to DBF include:

• Massive yield increases for farmers, who move from subsistence to business farming
• Taking carbon out of the air and storing it in the soil
• Reducing artificial fertilisers and pesticides over time
• Through the yield increases, less pressure on marginal land, which is left there, preserving biodiversity
• As more farmers adopt DBF, flooding is reduced in size and frequency, among other things reducing the silting damage to hydro-electric power
• Longer, deeper storage of water, available to plants far into the dry season