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The Permaculture of Soil, Part 3: Soil Care

Written by Caroline Aitken on . Posted in Uncategorized

So, what does it need in order to thrive and allow us to thrive? It needs to be left alone, as much as possible, to do what it does.

Do you dig?

When we advocate ‘no dig’ gardening in permaculture, this is what we mean. We don’t mean – “thou shalt not dig up thy potatoes” or that you’ll be struck by lightning if you double dig. The former is a necessary part of harvesting a crop, and of course must be done. The latter may be deemed necessary in certain circumstances – like bringing heavy compacted soil into cultivation for the first time- but it is damaging to the soil life (which mostly lives in the top 10cm of soil) and should therefore be avoided if possible. Having said that, once the structure of the soil has been improved it will be a better environment for soil life, this is why we don’t preach against digging when needed, just when it is done routinely, without question.

5. roots & hyphae
Plant root tips with delicate fungal hyphae and mycelium.

 

Digging or tilling the soil damages soil life in various ways. Earth worms are physically damaged and exposed to predators – likewise with larger creatures like beetles and spiders. Fungi produce large fragile webs of mycelium which connect up different rhizospheres (plant root systems) and transport nutrients between plants – this mindboggling system plays a huge part in how plants get their needs met, and can also be physically broken by working the soil. The smaller organisms such as bacteria and protozoa are harmed by being exposed to too much light and oxygen. When the soil is turned light and air flood in and eventually cause the microbes to die – these microbes are the foundation of this huge and diverse food chain.

 

dry ploughing

Dry soil being eroded by the wind as it is ploughed.

Digging is also, quite frankly, very hard work. Terrible for the back and knees, as I can personally vouch, and therefore not very sustainable in human terms either – do we need to return to a medieval life of drudgery? No we don’t. These big brains of ours can do better than that, and better than fossil-fuelling ourselves to extinction. On a larger scale digging means ploughing and apart from the obvious fossil-fuel issue of using large machinery, there are other costs: compaction, loss of soil structure and loss of humus are serious issues. Sadly in broad scale organic agriculture repetitive ploughing is often the primary method of weed control, other methods being unviable on a large scale (many things are unviable on a large scale, which is why bigger is not necessarily better).

wheat field rill

A ‘rill’ in a wheat field following heavy rain – the top soil is being washed away.

 

A fertile soil is about 50% pore space, ie: varying proportions of air and water depending on the weather and other factors. These spaces are essential for the life within to move about, breathe and take in water. If there’s no space, there’s not going to be much life either. Not only this, but once soil has lost its structure it is much more vulnerable to erosion by wind and rain. Here in Devon the red streak of earth running out of farmers’ gates is a common sight after heavy rain, and that is hundreds, maybe thousands of years worth of soil disappearing. But of course it doesn’t disappear, it ends up somewhere else – rivers, drains, sewers, mainly where it’s not wanted. Not only this, but when the whole world is ploughing, causing all those surges in microbial activity, huge amounts of CO2 are released into the atmosphere. So much so, that the emissions caused by the tractors driving the ploughs pale into insignificance. Some say that if the world stopped ploughing tomorrow we could halt climate change. Quite a thought.

 

What about the weeds?

A common reason for working the soil is to combat perennial weeds. Docks, thistles, creeping buttercup, dandelion, bramble – they all have something in common – they are vigorous, competitive and persistent, and they must be managed if we want our crops to thrive. They have something else in common too – they propagate very easily from root cuttings. Most gardeners know that if you break off the tiniest bit of dandelion or dock root when pulling them out, a new plant will grow before you know it. So what happens if you plough or rotivate? You increase these weeds ten-fold. Permaculture is all about forward thinking – creating solutions before there is a problem. Charles Dowding, the well known no-dig gardener and author advocates a zero-tolerance approach to weeding. Never let a weed get too big for hoeing if possible. Hoeing only affects the top centimetre or so of soil and causes very little damage to soil life.

mulch 14

Charles Dowding’s market garden; mulched with compost and regularly hoed.

 

How to Care for Your Soil

See it, feel it, smell it, know it.

Get to know your soil and understand what it needs, before doing anything else. Learning to take a soil profile or a texture test are two very simple ways in which we can get to know our soil, and they are well worth doing. A texture test will tell you about the mineral particles that make up your soil, and the different characteristics those particle combinations have. For example, a sandy soil is usually well-drained, possibly drought-prone and often acidic. A clay soil can be prone to compaction and waterlogging if the structure is poor, but responds well to improvements and is very fertile. These are the opposing poles of soil texture and there is a sliding scale of everything in between including silty soils and loams. Knowing the texture of your soil can have a big influence on how you manage it successfully. A profile sample can tell you many things, from the levels of organic matter to the depth of your topsoil and the structure. Looking at colour, smell, root penetration, soil life, crumb structure gives you a very comprehensive picture of what you’re dealing with. A PH test may also be worthwhile if you want to grow a wide range of fruit and vegetables, or plants which you know prefer a particular PH range such as ericaceous plants and the Brassica family.

Give it a good start.

If you are starting out with a soil that needs some form of improvement, you must get that soil into a condition where it can begin to thrive and become the growing medium you need it to be. If your soil is heavily compacted, there are a series of measures that can be taken depending on how bad the situation is. If it’s had a bit of footfall and just needs loosening up with a fork this can be done very quickly by working across the ground in rows (as if you were mowing the lawn), pushing a large fork deep into the ground and pushing forward, then puling back. You are not lifting or turning the soil, simply making holes into which air and water can penetrate, creating niches for life to take hold. Once the air, water and life have got in, they will do the work for you. If the situation is worse than that you could consider digging the ground over, and if you find your compaction issue is very severe, you may choose to double dig. You may need to dig or double dig for a couple of consecutive years or more to relieve the problem, but once the crumb structure is good, you may never need to do so again, and that makes it all worth while. Leave the soil to its own devices to recover and thrive.

 

mulching 2

Soaking the first layer of a 3-layer organic mulch: 2-3 layers of corrugated cardboard.

A great way to bring new ground into cultivation is by mulching. A clearance mulch is a non-living ground cover that blocks out light and kills off existing vegetation (weeds or grass) to clear the ground for growing what you want. If you want to increase the organic matter content at the same time I highly recommend using a three-layer organic mulch. The first layer is several layers of cardboard, followed by a 3” (8cm) layer of compost and/or manure, followed by a top layer of straw, or dried bracken, or whatever you have to hand that will form a barrier to weed seeds and protect the mulch as it does its work. After a full growing season the existing vegetation will have been killed off, the cardboard will have broken down and the worms will have mixed in the compost and manure, creating a beautiful, dark, rich topsoil. Peeling back the top matted layer to reveal this beautiful substance, really is a wonderful experience! You can gain further satisfaction by growing a crop in the space while the mulch is doing its job, although it’s worth following good instructions for the classic ‘3-layer organic grow-through mulch’ to ensure success (see The Earth Care Manual P195). There are many ways of mulching and many different materials that can be used. It’s worth experimenting and researching to see what will work for you.

Keep on top of it!

DSC02564

An annual polyculture of lettuce, squash and sweetcorn, mulched with straw.

To maintain your soil at a high level of fertility, which is necessary when obtaining a yield, you will need to routinely add more nutrients and organic matter. Organic matter has a limited life and needs to be replaced in the form of compost or well rotted manures. This is usually done in the winter when beds are empty or plants are dormant. It will gradually be worked in to the soil by the time plants begin growing in the spring. During the growing season you can use compost as a maintenance mulch to add fertility while also protecting the soil from erosion and water evaporation. The one drawback of using compost as a maintenance mulch is that weed seeds can get into it and grow happily. This means you’ll either need to take Charles Dowding’s approach and hoe regularly, or use a different material which will act as a barrier to seeds. Straw is commonly used, but be resourceful and use what you have on site if possible. We use Crocosmia and fern leaves cut from the previous growing season. By constantly working on top of the soil there is no need to disturb it, so you have a win-win situation of less work and healthier soil and plants. The key then is to make sure that you don’t have to actually get on top of it to keep on top of it. Raised bed systems are ergonomic growing beds that maximise top soil and minimise compaction. A raised bed doesn’t need to have physical ‘sides’ like planks or walls, it just needs to be the right size and shape to be tended with out being stood on.  The beds become raised when top soil is dug off the paths and added to the beds when they are created forming slight mounds. The beds are generally around 1m in width to allow access to the middle by reaching in from the paths. Over time the beds maintain their mounded shape as you add compost on top, and the increased topsoil depth allows closer planting and higher yields.

 

So it’s really very simple when you think about it. You begin by understanding the environment as a system. You think about what it needs, and what you need and find a way to become part of those systems – taking out and feeding back in. An ecosystem may be complicated but being part of it in a healthy and balanced way needn’t be. That is beauty of permaculture design and the wonder of nature.

 

The Permaculture of Soil, Part 2.

Written by Caroline Aitken on . Posted in Uncategorized

The Soil Food Web.1. web

In my last post I said that while organic matter constitutes the smallest proportion of the non-living components of the soil, it may have the biggest importance. This is because it’s the basis of the soil food web (the food chain of the soil ecosystem) and it has many special properties that enable life to thrive. Organic matter in the soil starts out as dead plant and animal material which either falls on to the surface or occurs beneath it (dead plant roots and soil organisms). These materials then go through various stages of decomposition thanks to a variety of soil organisms and eventually become a substance called humus. This dark brown/black goo is what gives a good soil it’s rich colour and to a large extent, its fertility.

Here are some of the ways in which organic matter affects soil:

Structure:

Most gardeners know that earth worms (lug worms) are their allies. Worms live in the top soil and come to the surface to find fallen plant materials such as leaves. They pop up and search around until they find something good, then they drag it down into their burrow, where they wait for microorganisms to help break it down so they can eat it. Their digestive system uses mineral particles from the soil to help to grind up the plant materials which means that what emerges from the other end of the worm is a gooey combination of decomposed organic matter and minerals – perfect soil! Simply by pulling organic matter from the surface in to the soil the worms are playing a vital role in incorporating it into the food chain. Other helpful behaviour is the burrowing that worms do, making thin channels through the soil which improves the structure and allows air and water to penetrate. The gooey nature of worm castings and humus helps to form aggregates by sticking particles together into ‘crumbs’. This makes the soil stable and less prone to erosion or compaction.

14. worm pulling leaf

An earth worm pulling a dead leaf down into it’s burrow

Improved structure means that the soil can hold on to water for the plants, but also be well drained and not prone to water-logging. Dead plant materials can be fibrous and hold water and air, while humus acts like a sponge, absorbing water and with it, nutrients.

Plant Nutrients:

Organic matter contains a certain amount of nutrients which plants need, but this varies according to what it’s made of. Often these nutrients are locked up in a non-soluble form that is unavailable to the plants, and are only made available via microbial activity which converts them to a soluble and available form. Once nutrients are soluble they are also leachable and will be washed away from the plant’s roots unless the soil can hold on to them. This is where the water-holding ability of organic matter is so important. The water held contains soluble nutrients – plant food. Humus has between 2 and 10 times the nutrient holding capacity of clay, therefore small amounts make a big difference.

Woody materials and tree leaves are generally consumed by fungi which form large networks of mycelium beneath the surface of the soil. Mycelium is the body of the fungi and the mushroom is the fruit. Soil-based fungi can spread over large subterranean areas and behave in a curious and wonderful way by connecting up the root systems of different plants. It turns out these mycelium networks function as an exchange between the fungi and the plants, and between different plants which are connected. Nutrients and water can be exchanged where there is an excess in one area and a need in another. This is how plants which can ‘fix’ nitrogen (via a symbiotic relationship with certain bacteria) can make it available to surrounding plants.

6. root tip & hyphae

Fungi attaching itself to the root tip of a plant

 

Adding organic matter to your soil is a great way to increase the fertility because it contains nutrients, it holds air, water and soluble nutrients and it gives good structure. The affect of organic matter in soil is disproportionate to its quantity.

Soil Life:

Organic matter provides food and habitat for the organisms that make up the soil food web. These organisms help to turn organic matter in to humus, the many qualities of which are outlined above. They also make the nutrients in that organic matter available to plants and other soil life. They are the invisible factory that recycles nutrients and enables natural self-sustaining systems. As the diagram shows animals, plants and fungi are interdependent, forming complex food chains, and many co-operative and symbiotic relationships. We take organic matter out of the system in the form of food, so to keep the system functioning we must replace that organic matter in a form that will feed the system- compost, manures, etc. Other than that we need to leave it alone to do what it does, and has evolved to do over millennia.

In my next post The Permaculture of Soil, Part 3: How do we care for our soil? I will give some practical guidance on looking after what you’ve got at home.

The Permaculture of Soil, Part 1.

Written by Caroline Aitken on . Posted in Uncategorized

What is it and why does it matter?

A couple of months ago I was teaching the students on Shift Bristol’s Practical Permaculture course about how to preserve garden produce. Apart from the usual jams, chutneys and syrups I also taught some basic traditional fermentation methods. Fermentation at home is not just about wine and beer but also about food. Sauer kraut, kimchi, kefir and kombuca are becoming more popular in Britain due to their interesting flavours and apparent health benefits. It was while explaining those benefits that I referred to our digestive system as:

“an ecosystem containing hundreds of different microorganisms which help us to digest nutrients from our food – just as the microorganisms in the soil ecosystem make nutrients available to plants.”

This comment triggered a wave of invisible light-bulbs above the students’ heads as they made the connection between soil and our digestive systems, the connection being microorganisms. Last time I was teaching the ‘soil food web’ on our Design Course I explained that the roots of plants are covered in a coating of bacteria which feed off the roots and are the basis of the soil food chain. I went on to say that the leaves are also coated with bacteria which form a healthy protective barrier against disease. A hand went up and one of the students rightly pointed out that “pretty much everything is coated with bacteria”. It’s true; these bacteria are an important part of our world, and we need to understand that.

teaming 34,99We are beginning to understand the complexity and importance of our intestinal flora, but still many people are unaware of the complexity of soil life. In recent years scientists such as Dr Elaine Ingham have made great leaps in our understanding of the soil, but you could say we have only scratched the surface. There are some fantastic books available to the layperson who wants to dive in to the subject, and if you’re interested I would highly recommend Teaming With Microbes by Wayne Lewis and Jeff Lowenfells and The Soul of Soil by Joe Smillie and Grace Gershuny, but we don’t need to know all of the science in order to know how to care for the soil. We just need to understand that we must care for it and that in doing so we’re caring for our own future.

There is a still a common misunderstanding about the importance of organic food production. It is not for nothing that the UK governing body is called ‘The SOIL Association’ and yet many consumers are unaware of the reasons for this. I have overheard many a conversation about whether organic food “really does tastes better”, and whether farming chemicals “really do cause cancer” and such like. My primary reason for growing food ‘organically’ (without chemicals and working with nature) is because I want to protect the environment so that I can provide for my family now and we can all do so in the future. You could say that soil is our most precious resource – certainly Mr Whitefield said so in his Earth Care Manual:

“It is the mother of all plants, and through them the animals, ourselves and civilisation.”

So what is this incredible substance upon which we are so dependent?Soil pie chartIt may come as a surprise to see that less than half of soil is made up of mineral – that is particles of the bed rock upon which it is formed. It may also come as a surprise to see that only a maximum of 10% is made up of organic matter. On a conventional arable farm that could be as low as 1%, so all of these proportions are variable, but the chart represents an average fertile soil. In Patrick’s words a fertile soil is one which has the ability to support healthy and abundant growth of plants, and to achieve this it needs all of the above components.

Mineral particles and organic matter form into ‘crumbs’ in the top soil and the size and nature of these in different soils is known as the crumb structure. It is the space between these crumbs, known as pore space through which air and water can penetrate and be available to plant roots. A plant ‘breathes’ from every part of its body and therefore needs access to air around its roots. It also needs a constant supply of water both as a nutrient and as an essential part of its body: plant bodies can be 90% water and it enables their vascular system to function.

The proportion of air and water contained in the pore space will vary according to the weather – after rainfall it will be largely water, after drought it will be mostly air. Plants can cope with these temporary fluctuations to varying degrees, so long as they are temporary. When soil compaction occurs (compression of the topsoil due to footfall, cattle grazing or machinery) the crumb structure is destroyed and all of the air space pushed out. Waterlogging leaves no space for air in the soil, depriving the roots of carbon dioxide. So that 50% portion of space is vital for plant survival, and that is why you’ll hear growers talking about ‘improving structure’. This can mean relieving compaction, improving drainage or increasing the depth of the top soil. Most plant roots will only grow where they have access to both air and water. The deeper the roots grow, the more potential there is for abundant growth.

Soil Compaction TheOrangeGardener.Org

Non-compacted soil (left) and compacted soil (right)

Structure can sometimes be confused with texture, another term used to describe different soil types. While the structure is about how particles are joined together, the texture is about the particles themselves. This is very simple in theory. There are three types of particle – sand, silt and clay. A soil which is dominated by one of these particles is known as that type of soil, for example if it’s predominantly made of sand it’s known as a sandy soil. However, soil is generally a combination of all three in varying proportions (unless you’re on the beach or in a clay quarry!). A fairly even mix is known as a loam, and a mix with a bit more of one type is called a ‘sandy loam’ for example. Different particle types have different characteristics, so it can be helpful to know what type of soil you have so you can care for it appropriately and grow what is suited to it.

Compost heapI haven’t mentioned nutrients yet, and you may be wondering why it wasn’t the first thing on the list. The idea that mineral nutrients such as nitrogen, phosphorus and potassium (N, P & K) are the single most important factor in plant growth has, as Patrick put it “the full force of the advertising industry behind it!” Companies who sell chemical fertilisers would have us believe that’s the case, and by bypassing several millennia of evolution by throwing fossil fuels at it they have succeeded in growing food that way. But in a natural fertile soil there are many parts of the jigsaw, and the thread that connects them is the soil life – those micro-organisms mentioned at the start. In my next post I’ll explain more about soil life and how it works. How chemical fertilisers work is by liberally dowsing the soil with synthesised nutrients (made using fossil fuels), a small percentage of which will make contact with plant roots and be absorbed while the rest is leached away by the rain, ending up in the water system where it becomes a pollutant. Apart from all of the many complaints we might have about this, it’s a highly inefficient way to produce food, requiring huge amounts of energy and water while also causing pollution, loss of biodiversity and food of a questionable quality.

Organic matter is the final piece of the pie, and although it’s the smallest it is possibly the most important. Patrick muses that it is the closest thing you can get to a panacea! The many reasons for this will be explained in my next post –The Permaculture of Soil. Part 2: The Soil Food Web.

Permaculture Design Course on Dartmoor