‘Why would you want to deny the earth your cauliflower stalk?’ Satish Kumar
At the end of a meal, many people will chuck what’s left straight into the bin along with any peelings etc from preparing the food. We throw away a third of the food we buy, but the tide is turning and more and more people are wanting to grow their own food in healthy soil, which is why making compost is so important. ’ Whatever type of soil you have, compost will improve it. I’ve heard people talk about compost as only a ‘soil conditioner’ in a rather disparaging way, as though somehow this was not really important. I think they mean that compost does not add much in the way of nutrients to the soil, but this is not the point. Soil conditioning adds life back to the soil; it is the most important thing that we can all do and it’s ridiculously easy.
Here are just some of the benefits of adding compost to your soil:
Makes healthy soil
Compost adds life in the form of micro-organisms Compost feeds your soil; which feeds your plants Using compost on your soil will dramatically increase the amount of life in that soil, both life that is visible to the naked eye and, more importantly, the life that can only be seen through a microscope. The addition of compost builds a healthy soil and so boosts the microbial activity, which provides food for hundreds of thousands of different species of fungi, bacteria and other organisms; these microorganisms are also food for a whole range of other organisms, which in turn have predators, which feed off them. What we can see when we look at compost are the creatures, mini beasts on the macro scale; you will need a magnifying glass to see the very small ones but many are obvious and well known to us. The soil microbes feed your plants and protect them from pests and diseases. Crucially this microscopic world is cycling nutrients from the compost materials into a form which the plants in our garden can easily assimilate, and holding them in the soil until the plants need them. Of all the soil organisms the worm is the one which we all recognise as invaluable for creating a healthy soil and the worm does indeed possess almost miraculous powers - both the compost dwelling species and the larger soil dwellers.
There are over 600 million bacteria (about a level teaspoon) in just one gram of soil
Compost changes the physical structure of the soil
Reduces the need to water
Compost improves the water holding capacity of free draining sandy soils Free draining soils – compost holds moisture and nutrient (mostly contained within the microorganisms) helping build the soil ecosystem. If soils cannot hold water then plants wither and die, so increasing the water holding capacity of soils is a fundamental and dramatic advantage.
Compost opens up clay soils
Clay soils and compacted soils– compost helps open up these soils enabling them to breathe. Soils that cannot breathe become anaerobic (without air) and without air organic matter in the soil, organic matter can ferment with anaerobic microorganisms producing all kinds of by products toxic to plants, e.g. alcohol.
Buffers the pH
Compost ‘buffers’ the extremes of acidity and alkalinity in a soil
Healthy, humus-rich soils also ‘buffer’ the extremes of acidity and alkalinity, meaning that you can grow a wider range of plants that would otherwise be less tolerant of the degree of alkalinity/acidity of your soil.
Reduces the need for fertilisers
Humus improves cation exchange capacity (known as CEC) in soils – put crudely, as well as holding moisture (absorption) in the soil, humus holds a negative electrical charge which attracts positively charged nutrients (known as adsorption) making them freely available to the plants. Clay soils have strong cation exchange capacity and can be extremely fertile as a result, however they compact easily and without enough aeration they are not productive; the addition of compost is ideal for ‘opening up’ heavy clay soils. Most plants growing in a healthy soil form symbiotic associations with the soil mycorrhizal fungi – the fungi takes compounds exuded by the plant and in exchange the plant takes minerals and nutrients from the fungi. Some plants also form associations with bacteria, the most well known of these are the azobacters which help leguminous plants uptake of nitrogen. Conversely adding chemical fertilisers and pesticides to soils kills off soil micro flora and fauna. Chemical fertilisers are salts, which are more ‘salty’ than sea salt, and too much salt will kill off most plants and herbicides and fungicides will kill off other soil organisms; it can be the surfactants, (eg soap, which is often used to break the water tension) not the active ingredients, which smother and kill the microbes.
Reduces the need for pesticides
Healthier plants mean less toxic pesticides Adding compost and compost tea to soils and plants enables them to resist all kinds of pests and diseases. It is not really in the scope of this book to go into this fascinating area but all kinds of tests have been done using compost and compost teas and just how compost helps prevent pests and diseases is becoming more widely understood. The soil food web is incredibly complex and it is the soil organisms themselves that are supplying the nutrient in exactly the right form and location to the plant, right to its feeder roots. Bacteria form a protective layer around the plant root hairs, preventing viruses and diseases from getting in. The mycorrhizal fungi also form a barrier around the roots so that they can exchange nutrients with the plants. What is going on in healthy soil - which is quite amazing – is an incredibly complex subject and worth several books in its own right. One of the best contemporary authorities on this area is Elaine Ingham; her website www.soilfoodweb.com is well worth a visit.
Reduces the need to dig
You can never have too much compost in a no-dig garden. To start off you will need to import as much bulky organic matter as you can, in the form of commercially produced compost or well rotted farmyard manure; so making your own to top up the system is vital and will save you money.
Sequesters carbon sequestration
Compost locks up carbon Well-made compost becomes humus, which consists of long stable carbon chains with properties still not fully understood. This carbon is locked up in the soil for a very long time, as long as it remains in the soil and the soil is not ploughed or dug up; if it is it will combine with atmospheric oxygen and be released as C02 gas.
By creating a living compost to feed your soil you are also feeding a whole food chain right up to top predators. A healthy soil will have a thriving worm population, which is also food to many birds and other animals. The compost heap itself is full of life – indeed I like to think of it as a living organism in its own right - and the warmth of a compost heap can also attract slow worms and snakes and many other animals looking for a free feed, along with all the other invertebrates and other creatures great and (mostly very) small.
Think of all the reusable or recyclable materials that we put out for collection. We cannot reprocess glass bottles and tins at home but we can, nearly all of us, make compost and save many lorries having to truck all that material either to be composted centrally, or worse, incinerated. With landfill sites filling up, Local Authorities have been bringing in recycling and compost collections but even the best Local Authorities can only divert about half of the waste from landfill or incineration. The wastage of food is still huge, with around 20 percent of all waste being food and about a third of that waste is food thrown out, still unwrapped and within its sell by date. It is obviously far better to eat food rather than waste it; as people start preparing more food from scratch the amount of food waste in the form of peelings and tops and tails from vegetables actually increases which, unless it is home composted, increases the amounts having to be dealt with by the local Authorities – but why give this precious resource to the council to deal with when we can transform it ourselves into compost!
No need for fertilisers, pesticides or bought in compost Making compost at home saves money in so many ways. You don’t have to buy in compost and growing media, or fertilisers – make them yourself.
Summary • By making compost you are multiplying beneficial microbes, which replenish and feed the microbial activity in your soil, the microbes in turn help feed your plants. In other words compost feeds your soil; which feeds you plants
• The soil microbes not only help feed your plants; they also help to protect them from pests and diseases.
• Compost opens up clay soils and improves the water holding capacity of free draining sandy soils.
• Compost ‘buffers’ the extremes of acidity and alkalinity in a soil meaning you can grow a wider range of plants on your soil
. • Much of what we are currently wasting was once living material, whether that is cardboard, paper, fruit and vegetable peelings, food waste or garden prunings, clippings, weeds and so on.
• It saves you money, in that you don’t have to go out and buy chemical fertilisers and you should find with healthier plants that you don’t have to use any toxic chemical pesticides.
• You also won’t have to go out and buy composts as you can make you own soil improver, potting composts and more.
• Why give all your potentially compostable material away to the council? Even if they are going to compost it you still won’t get the benefits of it. And if it’s destined for landfill then stop your dustbin smelling and save all that material from being buried in a landfill site or sent up an incinerator flue.
• Sequesters carbon – locks up carbon in the soil rather than releasing into the atmosphere.
• Making compost is ridiculously easy; it’s satisfying and fun, once you get hooked!
Extract from Nicky Scott's book How to make and use compost in spaces big and small