Organic Gardening and Composting

For many traditional gardeners, the recent increase in the popularity of ‘organic’ gardening appears to have brought with it some rather extreme notions; it would be easy to believe that to garden organically, your garden has to resemble a municipal dump. Let me assure you otherwise. For me, organic gardening is simply gardening the way that nature intended; where natural processes are adapted to garden use and as much natural material as possible is reused or recycled. I believe that I garden organically and yet, in my own garden, there is not a car tyre or roll of old carpet in sight. In truth, all good gardeners have always been organic in their methods, and much of the current misconception and misunderstanding seems to stem simply from too rigid an adherence to definitions. I don’t mind what name you give to it, I simply hope that you will garden with common sense.

It seems easy enough to define as organic any material ‘derived from plants or animals’. Composts and manures are, by definition, of plant and animal origin and they are vital to a well functioning garden for their role as physical soil amendments. So everyone who makes their own garden compost or digs in manure in the autumn is certainly gardening organically in one sense. That much is straightforward. Where matters become confused is in the consideration of the rather more refined materials that constitute fertilizers and garden pesticides. General advice on their use is given elsewhere in the site, but I feel it is appropriate for me to consider here the organic considerations that may be involved in your choice.

People who have a practical or emotive aversion to using synthetic chemicals turn instead to ‘natural’ products; using fish, blood and bone as a general fertilizer instead of Growmore, for example, and pyrethrum instead or malathion as an insecticide. I offer no dogma on the subject but would simply like to draw your attention to some less obvious facts that you might wish to consider.

When selecting fertilizers, remember that they all break down in the soil into much more basic components. Plants absorb nitrogen, not dried blood or ammonium sulphate; and chemically, there is no distinction between nitrogen from one or other source.

Many animals are raised by intensive-farming techniques and fed synthetic foods and medicines during their lives, so does this render their by-products, such as bone meal or dried blood, unacceptable for use in the garden? And while it must be accepted that the manufacture of synthetic chemicals can be despoiling to the environment and inefficient in terms of energy use, it is only fair to ask if this is more or less acceptable than the despoiling of the environment that occurs in the extraction of such natural products as guano or limestone.

In choosing an insecticide of natural origin such as derris, do be aware that some of the most toxic chemicals known to man are similarly of natural origin, that materials like derris occur naturally in immeasurably lower concentrations than you are applying to your plants (with consequently very different effects), that derris is undiscriminating in its action, killing good and harmful insects with equal efficiency, and it is very poisonous to fish. As I have said, I offer no dogma and where you choose to draw the line on what is and isn’t acceptable to you is a matter of individual choice. But make sure that you are in possession of all the facts.

Compost and compost making

I consider a functioning compost heap to be at the heart of any well-managed garden. The process of composting transforms garden waste into a valuable material that can be returned to the soil again. And on a purely pragmatic level, composting reduces the need to dispose of rubbish in dustbins or by visits to the local tip and is, of course, more ‘friendly’ both to the environment and to neighbours than a bonfire.

But rather than simply returning fresh organic matter straight back to the soil, it is better to allow it to undergo the first stages of decomposition in the controlled conditions of a compost bin. By isolating the material at this stage, when the decomposition bacteria require a boost of nitrogen in order to function, the soil is protected from the risk of nitrogen there being temporarily depleted.

slatted wooden compost bins allow good aeration and help decompositionThere are a number of designs of compost bin, but I prefer the traditional wooden type with slatted sides to allow adequate aeration, which is the key to successful compost making. Don’t be tempted to buy the smallest bin available; within limits, the larger the mass of material, the more it will retain the heat required for decomposition. I recommend a wooden, slatted compost bin of about 1.2m (4ft). If space permits, choose a double bin; as one container is being filled, the other is maturing for use.

Most organic waste from the garden and much from the house can be added but among the few substances that are best avoided are those materials that will not break down, such as plastic, metals or minerals, and glossy, plasticised paper. It is said that animal remains such as chicken carcasses might attract vermin, but I bury them in the centre of the heap, among lawn mowings for instance, and have experienced no problems. Large quantities of leaves break down more slowly than most organic matter and are best slacked separately in a wire-netting leaf mould cage, also of about 1.2m (4ft) to make mulching material. Newspaper and woody materials, such as prunings, should be shredded first to aid decomposition, while lawn mowings are best mixed with coarser material; and compost made from them shouldn’t be used within two months of applying lawn weedkiller.

A proprietary compost ‘accelerator’ or fresh manure will provide the initial supply of nitrogen that the bacteria require, and should be applied after every l5-20cm (6-8in) layer of organic matter has been added. The material should be kept moist but not waterlogged and natural rainfall should provide enough moisture, but it may need to be supplemented during dry spells. During periods of heavy rain, a plastic sheeting top will prevent water-logging. I have never found it necessary to add soil or lime to a compost bin but the contents of the bin should ideally be turned at least once. In practice, it is easiest to turn the material about three weeks after it has been added. Compost should be ready to use after about six months, but the speed of decomposition is temperature-dependent so it varies both with the time of year and type of material.

Other soil amendments

Even the keenest re-user of waste material will find it difficult to make enough garden compost for all of their mulching and soil-improving needs, so most of us require some additional materials. In making your choice, however, whether from a local source, branded products from a garden centre or by mail order, choose wisely. Don’t be swayed by claims of ‘essential plant foods’ and ‘enriching the earth’. What you require is an economical, bulky product that will open up the soil and provide a source of humus (and ideally, a small amount of nutrient). Be wary of products that recommend very low application rates; all proven, practical soil amendments for garden use work properly only if added in fairly large quantities. I have summarised the salient features of the commonest organic materials in the Table below to assist you in making your choice:

manures and practical considerations and approximate N:P:K nutrient values

Mulches and mulching

Mulching offers a method of weed control that doesn’t rely on chemicals, a way of retaining moisture within the soil, a protection for plants against penetrating frost, and, if organic mulches are used, a convenient method of applying bulky organic matter with minimal labour. A mulch is simply a layer of material placed over the surface of the soil. The material can either be loose, garden compost, leaf mould or manure, for example, or, like paper or plastic, laid in sheets. A loose mulch should be applied in a layer at least 5cm (2in) thick and will need replacing twice a year as it breaks down. The ideal times to apply mulches are in early spring, when the soil should still be wet with winter rains yet has started to warm up, and in autumn when rain will again will have soaked the soil yet winter cold will not have begun to penetrate.

The so-called no-dig system is becoming popular amongst some vegetable growers and, in one of its manifestations, depends heavily on organic mulching. The essence of the operation is to walk as little as possible over the soil surface, minimising compaction and removing the necessity for regular digging. Organic matter is applied either by mulching and allowing earthworms to incorporate it in the soil or by occasional double digging. I don’t believe that plastic-sheet mulching, an unsightly, environmentally unfriendly activity, is justified other than for the control of persistent deep-seated weeds. For every other use of a plastic mulch, an organic blanket will serve equally.

30. July 2013 by Dave Pinkney
Categories: Garden Management | Tags: , | Comments Off on Organic Gardening and Composting

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