It is our intention to make this faq section of our web site topical and informative on a wide range of soil, earth and compost related issues. Use the links below to view the current topics and book-mark this page for future reference.

By increasing the biological activity and therefore CO2 production in soil are we increasing the concentration of CO2 in the atmosphere and contributing to global warming?

What is wrong with using peat-based materials in the garden?

How can I start to recycle my kitchen waste?

Are there any simple tests I can do to check the health of my soil?

Why are chemical fertilizers harmful to the environment?

Are there any generally accepted standards for compost?

I've seen topsoil for sale in garden centres - how do I know if it's any good?

By increasing the biological activity and therefore CO2 production in soil are we increasing the concentration of CO2 in the atmosphere and contributing to global warming?

First some background information……

All living organisms, whether human or microbe, produce CO2 gas as a by-product of the process of respiration. In nature this process is balanced by the uptake of CO2 by plants. This is called photosynthesis and it occurs in the green leaves of all plants. As a result of photosynthesis CO2 is converted back into organic carbon in the form of grass, trees, grains and vegetables.

The system is a dynamic one: every year one quarter of the carbon in the atmosphere moves to and from the surface of our planet. Incredibly, until around 1750 when the Industrial Revolution came along, the movement of carbon in and out of the atmosphere was balanced, and as a result the concentration of CO2 remained constant for thousands of years.

This natural balance was upset by the increase in release of CO2 from fossil fuel associated with the arrival of man's industrial activity. Together with the clearing and burning of forests this has led to a steady increase in the concentration of CO2 in the atmosphere over the past 250 years.

The United Nations Intergovernmental Panel on Climate Change predicts that this increase in CO2 concentration in the atmosphere will lead to an average increase in global average temperature of around 0.2 oC every 10 years. If this continues then it will affect everyone's way of life.

So what about the question?

It seems that the major factor causing this trend of increasing global temperature is the release of CO2 from fossil fuel combustion, not the release of CO2 from soil respiration.

We should however take a responsible attitude to the potential contribution of soils to the problems of global climate change. There are several positive aspects to this.

We can only increase the biological activity of soil by feeding the microbes with organic materials such as compost. Maybe half of this organic matter will remain in the soil as humus and as a result will increase the store of carbon in soil. This is a good thing. The rest of the carbon will be converted into CO2, which may not be so good.

We should therefore balance this increased soil respiration by planting trees to convert CO2 back into organic plant material. Planting trees is one of the most important ways of combating global climate change.

Finally, the only alternative to converting our green waste material into compost and using it to improve our soil is to bury it in enormous holes in the ground. The problem with this is that the green waste is converted into methane gas which is 7.5 times more damaging to the atmosphere than CO2.

To summarise

1. Converting green waste into compost and using this to improve the biological activity and organic matter content of soil is the most environmentally friendly way of managing these resources.

2. Planting trees will help to neutralize any greenhouse effect caused by increased release of CO2 from soil.

Further information

The book Global Warming The Complete Briefing written by John Houghton in 1997 is a clear, concise and comprehensive guide for non-technical readers. It is published by Cambridge University Press.

Future Forests is an organisation which encourages and facilitates the planting of trees to balance the amount of carbon dioxide produced by any particular activity (www.futureforests.com/index2.html)

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What is wrong with using peat-based materials in the garden?

It's confusing, but the compost that's sold in garden centres doesn't come from a compost heap. Most of it comes from peat bogs in the UK and Ireland. Peat is formed from the remains of plants such as sphagnum moss, and is preserved under the cold, wet and acidic conditions found in a peat bog.

Peat bogs provide an important habitat for a whole range of birds, insects and plants. They also provide an important record of the climate, as well as the plants and animals that lived in the peat, over the past 10,000 years.

The problem is that the peat bog is being threatened: some people want to plant trees on it, others want to bag it and sell it to gardeners. Lowland raised bogs are particularly vulnerable with only 6% now remaining unaffected.

It's for these reasons that the Royal Society for the Protection of Birds and the Worldwide Fund for Nature UK are calling for an end to peat extraction. This is being taken seriously by organisations such as National Trust, which is setting an example by phasing out its use of peat-based materials.

But why are UK gardeners buying more and more peat-based products? The main reason is that peat makes an excellent growing medium and is suitable for a range of purposes. You can rely on a bag of potting compost to perform consistently. The equivalent of 60 million bags (40 litres each) are sold in the UK every year!

But peat isn't actually a very good source of nutrients for plants. It contains very little biological activity so the manufacturers add nutrients to boost its chemical fertility. It's really the gardeners equivalent of modern-day intensive farming - effective in the short term, but with the possibility of serious environmental problems.

A more sustainable way to meet the demand for growing media and soil conditioners is to use locally produced compost. Composting provides a way of converting unwanted materials such as kitchen and garden waste into rich humus. In this way we can do our bit to recycle green waste and at the same time help to protect an important natural habitat.

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How can I start to recycle my kitchen waste?

First some background information ……..

Each person in the UK produces on average half a tonne of household waste every year. More than 50 per cent of this waste, including a large proportion of packaging, could be recycled, but at present we dump 85 per cent of our rubbish in enormous holes in the ground (known as landfill). Things have to change - under a new European Landfill Directive the UK Government will be required to reduce the amount of rubbish going into landfill by 60 per cent over the next 15 years. As a result, there's going to be a Rubbish Revolution on our doorsteps as the Government gives a massive boost to compulsory recycling.

The UK has a long way to go to catch up with other countries in Europe. In the UK at present only 8 per cent of household waste is recycled by councils, compared to 45 per cent in the Netherlands. The plan is to double this figure by the year 2003 to recycle 5 million tonnes of household waste. Almost 25 percent of household waste is food and garden waste such as leftover food and vegetable scraps. This material, sometimes called 'green waste', can be easily made into compost and then used as an excellent natural fertilizer which will improve the quality of soil.

So what should I do about my kitchen waste?

The most important thing is to avoid putting kitchen waste into the dustbin along with all the other rubbish. That means collecting all your food scraps and keeping them separate from other waste. You then have the option of:

The thing that puts most people off collecting their kitchen waste is the smell and mess from rotting food. We can help you to overcome this problem with our 100 % compostable Food Cycler Bag. It is environmentally-friendly, smell-free, leak-proof and fully biodegradable and provides a convenient, hygienic way to assist you recycle your kitchen waste.

For further information visit our on-line catalogue.

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Are there any simple tests I can do to check the health of my soil?

What most people don't realise is that soil is a living material. So we can start to think of soil in the same way we that we think of any living organism. We can even give a soil a health check to make sure everything is OK.

Earthcare Ltd is in the process of developing a soil health check which will help gardeners, growers and farmers monitor the health of their soil, and at the heart of this concept is our Garden Care Kit which allows you to measure how well your soil is breathing. We breathe in order to take up oxygen and release carbon dioxide. Soils do the same! And we know that the more active we are the more rapidly we breathe (we call this respiration). A soil in which the microbes are working hard converting complex molecules into simple ones that plants can use will produce carbon dioxide as a by-product. The more active the soil population, the more carbon dioxide is released. So we can use the amount of carbon dioxide produced by soil as an indicator of the health of the soil. Of course if in some terrible way the soil population is killed, then the soil stops breathing.

To keep our soils in top condition we need to think about ways in which we can feed the soil population. This means using organic materials such as compost and green manures to increase biological activity. We must also ensure that the soil inhabitants aren't exposed to any nasty chemicals which may be toxic to the population.

Another very useful indicator of soil health is the pH or the balance of acid and alkali in the soil. We know how unpleasant it can be when this balance is upset in our own tummies - indigestion can be remedied by taking neutralising tablets. The same applies to soil - if the balance is wrong and the soil becomes too acidic organisms such as earthworms find it uncomfortable. This can be detected by measuring the soil pH with a pH test kit. A pH value of 7 means that there is a balance between acid and alkali (it is neutral). We should try to ensure that the pH of soil is close to neutral, and if it is too acid then we can add lime to correct the balance. In the case of flowers and ornamentals it is important to know whether they prefer slightly acidic or alkaline conditions. Certain plants have very specific requirements for this, and will do badly if the soil does not have the correct pH.

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Why are chemical fertilizers harmful to the environment?

The benefits of using manure and legumes to improve the fertility of soil has been known for thousands of years. But it is only in the last hundred years or so that advances in chemistry have allowed scientists to analyse these materials. Manure is rich in N, P and K, legumes are rich in N. So scientists have developed chemicals which contain these elements, but in a simpler and more concentrated form. These chemicals are sometimes referred to as artificial fertilizers.

Chemical fertilizers are convenient, and have been widely used in many parts of the world to increase food production. But part of the the problem lies with the fact that these chemicals are so convenient. Chemical fertilizers are a bit like the medicines we take when we are ill - they dissolve easily in water and are rapidly taken up into our blood, but there is a danger of taking an over-dose. Nitrogen fertilizer, for example, dissolves in the soil and provides a high concentration of nitrogen in the form of ammonium or nitrate. The plant will take up what it needs but what happens to the rest?

This is the key to the problem - the chemical fertilizer remaining in the soil can easily move into water or the air. As a result the environment can become polluted - rivers can become too rich in nutrients causing a decrease in the amount of oxygen for fish to breathe (this is called eutrophication).

Also, chemical fertilizers do nothing to promote biological activity in soil.

So what is the alternative?

In natural ecosystems such as forests N, P, K and all the other elements required for plant growth are supplied, with the help of soil microbes, by the soil organic matter (sometimes referred to as humus). The supply of these elements is matched to the needs of the plants, and therefore there is less chance of excess nutrients being produced and polluting the environment.

By using organic fertilizers such as manure and compost we can learn from nature and can reduce the risk of polluting the environment, and ....

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Are there any generally accepted standards for compost?

There's going to be a lot more compost for sale in garden centres and DIY stores over the next few years as more and more household/garden waste is recycled. But when faced with a choice between peat and compost how can you be sure the compost is any good?

Compost feeds the soil population, and leads to a build up in the long-term fertility of the soil. It provides energy and nutrients for the soil microbes enabling them to grow and multiply and supply N, P, K and micronutrients in a balanced form. Microbes also assist in the formation of good soil structure which is important for the supply of air and water in the soil.

Various organisations are currently putting together standards for compost based on detailed analysis of the individual components e.g. nitrogen (N), phosphorus (P), zinc (Zn). The main concern is that the compost might contain nasty things such as toxic metals or weeds and diseases.

The Soil Association has set limits for the concentration of potentially toxic elements such as copper if compost is to obtain their approval. The UK Composting Association and the European Commission have proposed additional limits for certain dangerous bacteria, and weeds. Information on a whole range of other properties will also be required.

It is important that the compost you buy is mature - this means that the microbial activity responsible for making the compost has stopped. Immature compost can seriously damage the growth of plants, and should be avoided. The Solvita Compost Maturity Kit enables producers to measure the maturity of a batch of compost and helps ensure that the final product is of the very best quality.

When these standards are fully operational they will allow you to buy compost confident in the knowledge that the product is not only good for your soil and plants, but is also environmentally safe.

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I've seen topsoil for sale in garden centres - how do I know if it's any good?

If you're spending money on a bag of soil you want to be sure it's the real thing. How can you be sure?

The British Standards Institution has produced a specification which says what topsoil should and shouldn't contain1. Three grades of topsoil are defined in terms of the solid material (stones, sand, silt, clay), plant nutrients (N, P, K), organic matter (humus), acid/alkaline balance (pH). The soil should also be free of weed seeds, glass, bricks and other rubbish.

So if the soil you are buying meets British Standard 3882 Premium Grade specification then it should be suitable for all gardening purposes.

This is all very well except that it doesn't take into account the fact that soil is a living material. We know that if soil is stored for a long time the biological activity decreases. Like any biological product, bags of soil should have a use-by date - but they don't. Even more surprisingly the soil may have been sterilized to eradicate all signs of life!

What about other certification bodies? The Soil Association, the UK's leading campaigning organisation for organic food, provides certification of organic quality. Although there is no organic standard for soil, soil management techniques are specified. One of the guiding principles of organic systems is that soil fertility should be based on biological processes.

It's for these reasons that Earthcare recommend that any soil you buy should be tested for its biological activity. This will give you an indication of the health and long-term fertility of the soil, and help you to spend wisely.

BS 3882 (1994) Specification for Topsoil can be obtained from the BSI 389 Chiswick High Road, London, W4 4AL.

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