Soil Improvement–Mulching, Manuring, Composting And Fertilising

The quality and richness of the soil is vital for food production in a self-sufficiency set up. Without good soil you cannot expect to grow good crops. Treat it as though it were your bank account and remember that you cannot keep drawing cheques unless you pay some money in from time to time. Fortunately often we can both enrich the soil and save ourselves a little work at the same time. Take mulching for instance A mulch is a cover spread over the surface of the soil. Newly-planted fruit trees and shrubs were traditionally mulched with strawy manure immediately after planting. This practice continues to this day. The mulch protects the newly planted tree or shrub from frost damage in winter and from summer drought. At the same time, the rotting manure supplies the young tree with plant food.


Mulching may be practised successfully in other ways. Most mulches inhibit weed growth; all mulches conserve soil moisture. Thus, a mulched garden needs less time and work to keep it weed-free and watered. During both winter and summer, mulched soils are protected from extremes of temperature. In winter, a mulched soil seldom freezes; in summer, mulched soils are cooler and wetter. Summer mulching is more popular than winter mulching. The practice is of great advantage in the drier eastern half of the country where the conservation of soil moisture is so very important.

mulching with peat and manure

Many materials used for mulching purposes disintegrate slowly and add valuable minerals to the soil. Where garden compost or strawy manure are used, the first heavy rain will wash some plant nutrients into the soil. Many plants, notably cucumber, vegetable marrow and tomato, will send adventurous, new feeding roots into the manure or compost. Granulated sedge peat, itself a soil im-prover, is a neat mulch in the flower garden. A 1-inch thick layer is sufficient for the season. Peat may also be used in the vegetable garden and is recommended for the strawberry bed.

Straw is also a suitable mulch for fruit and vegetable gardens but it is not of use around seedlings which it may smother. The rotting straw from summer mulches may be dug into the soil during winter digging. Autumn leaves make an excellent mulch to prevent the growth of annual weeds on temporary paths in the garden. Wood shavings and sawdust serve the same purpose. These materials rot down well and disintegrate within three years of their application. Although the use of leaves, wood shavings and sawdust is not generally recommended for mulching growing plants, autumn leaves may re-place straw around established fruit trees and shrubs. Lawn mowings may be used for mulching in all parts of the garden but, if these are obtained from an outside source, you should make sure that no weed-killer or hormone spray has been used on the lawns from which they come. These substances are so persistent that broad-leaved plants mulched with lawn clippings containing minute traces of them, may be seriously damaged or even killed.


Manure may be defined as any substance applied to the soil to make it more fruitful —a term which may also be applied to fertilisers; so really it is without precise meaning. But we generally think of a manure as a bulky, humus-forming substance that is formed from animal or vegetable origin or in other words, it is a ‘natural’ manure.

Some bulky manures are inconvenient to handle, usually smelly and expensive to buy. So, will we get better plants, more nutritious vegetables and fruit, and do a better job of conserving soils if we use organic manures instead of relying solely on factory made or ‘artificial’ fertilisers that supply plant foods alone? The answer is that bulky organic manures add to the content of organic matter, which plays a vital role in building and maintaining soil fertility. Every time you dig, hoe or cultivate a soil you let more air in. Then the soil organisms become more active and these break down organic matter, which is their food, and soils often lose their structure and become more difficult to work and soils on sloping ground often erode.


When first applied, the fibrous material opens up all soils making them more porous, better aerated and drained. Small animals and minute organisms break them down and in so doing produce waste products that bind and cement small particles together to form clusters and in some soils porous crumbs. These have large spaces between them that hold moisture yet allow surplus water to run away. The minute spaces within the crumbs hold moisture and plant foods available for plant use. A soil with a good crumb structure does not fall to paste when rained upon nor does it crush easily when cultivated.

Humus is one of the end products of decay. It absorbs many times its own weight of water and this helps sandy soils to hold moisture better —an effect that is most noticeable in dry periods. Close- grained soils, either silts or clays, which tend to pan or are difficult to work, are much improved. Garden compost, farm-yard manure and most other organic manures also supply substantial amounts of plant foods —nitrogen, phosphates and potash and many others including trace elements. But being formed from plant and animal residues they differ from most factory-made fertilisers because their nutrients are not in a form that can be used by plants. For example the nitrogen may be part of a complex protein molecule and as such it cannot be absorbed by a growing plant. As the material begins to decay, the nitrogen in its proteins under-goes chemical change and is eventually converted into ammonium and nitrate forms that may be absorbed by plant roots. While these forms of nitrogen are exactly the same, whether they come from an inorganic fertiliser or a manure, they are released at a slow and steady rate over a very much longer period. This long-lasting effect is now being imitated in some of the newer synthetic organic fertilisers.

As ‘natural’ manures are long lasting in effect they are not exhausted as quickly as inorganic fertilisers, and generally leave useful residues for crops that follow. This is important to remember when planning vegetable rotations; cauliflowers and many other vegetable crops thrive in soils generously manured with organic manures, while others prefer the residues from a previously well-manured crop—a fact that leads to economy in the use of bulky manures.

Apart from the incorporation of manures in the soil before planting or during the life of the plant these materials are of great value when used as surface mulches. Mulches are like a blanket in retaining moisture. Water vapour from the soil surface diffuses very much more slowly through a loose mulch than it does from the bare soil surface. A wet bare soil can easily lose inch of rain in a week, whereas a mulched soil will take about six weeks to lose this amount.

Mulches usually allow water to penetrate soils more easily, the raindrops trickle slowly through the fibrous material and do not compact the soil as badly as they do when falling on bare soil. So mulches are of particular value to silty soils that are subject to surface panning through heavy rain. On such soils even a very light mulch will break the force of rain and prevent compaction and, by protecting the surface from exposure to rain, lessen the chance of cracking.

The best-known organic manure is farm-yard manure, but rotting plant remains, usually called composts, are manures too, and undecomposed materials like straw may be included .

Organic wastes from industrial processes, town refuse and sewage sludges are also offered as organic manures.

Not all organic manures are perfect. Some may have a bad effect on plants. For example straw, sawdust and even very strawy farmyard manure. These contain only a very little nitrogen but a lot of carbon and hydrogen, in the form of carbohydrates such as cellulose. But the attacking organisms need supplies of nitrogen while they feed on the carbohydrates and if extra nitrogen is not applied, they will take it from the soil and rob the plants.

This effect can be overcome by adding extra nitrogen to materials of this kind or by allowing them to undergo a partial decay before they are mixed with the soil.

Farmyard manure (FYM)

farmyard manure

Foldyard manure and dung are names used to describe a mixture of the excreta of farm animals and the straw or other litter used in yards or stalls to absorb the urine and to keep the animals clean.

If you live in a livestock-producing rural area it is easy to get a load of manure delivered to your garden. The average 3-ton lorry usually holds about 5 cubic yards of manure which is sufficient for 500 square yards of soil so that may be too much for your garden and it is necessary to share the load with a neighbour; a cubic yard weighs anything from 10 cwt to 15 cwt according to the amount of straw contained and the age of the manure.

The main trouble, of course, is getting the manure into your garden. You need a gate at least 7 feet wide for lorry or tractor and trailer access otherwise the manure has to be dumped outside the garden and barrowed in rapidly to prevent it from becoming a nuisance to passers-by. Five cubic yards of manure which is sufficient for about 500 square yards of soil so that may be too much for your garden and it is necessary to share the load with a neighbour; a cubic yard weighs anything from 10 cwt to 15 cwt according to the amount of straw contained and the age of the manure. The main trouble, of course, is getting the manure into your garden. You need a gate at least 7 feet wide for lorry or tractor and trailer access otherwise the manure has to be dumped outside the garden and barrowed in rapidly to prevent it from becoming a nuisance to passers-by.

Town gardeners are hindered by the problems of access and the high cost of transport. Even so, many town gardeners do buy FYM, either directly through manure contractors or through garden centres. Composted farm manures that are sold in bags are an obvious alternative to the fresh bulky material direct from the farm.

Quality of FYM

Like all organic manures farm-yard manure can vary in many ways from load to load, in contrast to inorganic fertilisers that have a fixed and definite composition.

The type of animal producing the dung has a big effect on quality. The dung (the solid excreta) of horses is the richest in all nutrients and it is drier than that of cows or pigs, so that the bacterial changes during rotting are much more rapid and a greater amount of ammonia is produced. Horse manure when stacked soon begins to steam showing that fermentation is going on; so it is called a ‘hot’ manure. It is specially suitable for mushrooms and for greenhouse work.

Pig dung is the next richest, followed by cow dung; both of these are much wetter than horse dung and in consequence heat up more slowly and are referred to as ‘cold’ manures.

So far as nutrients are concerned, farmyard manures are weak; for example you need about 50 lb of horse manure to supply as much nitrogen as there is in 1 lb of sulphate of ammonia. The average analysis of most farmyard manures is about per cent nitrogen, per cent phosphates and per cent potash. All animal manures contain in addition useful amounts of magnesium and calcium and are very good suppliers of trace elements, together with other substances which are believed to have growth-promoting pro-perties.

Quality also depends upon the kind of litter used for bedding. The most com-monly used litter is straw, which absorbs about three times its own weight of urine and of course provides additional humusforming matter. Peat moss is an even better absorber of urine and makes a manure which is easily spread and mixed with the soil. Sawdust and wood shavings are poor absorbers of liquids and are very slow to break down in the soil.

Benefits of manure

In view of the fore-going you may well think that in a space age it is an archaic practice to use farm-yard manure at all. But the results of experiments with good quality products show that it is the yardstick for comparing all other organic manures. In addition to its content of plant nutrients it is a humus supplier and for every ton you buy you will get about 3 to 5 cwt of organic matter which soon becomes humus in the soil and gives all the benefits associated with humus. It supplies its nutrients in a slowly available form and, therefore, has a long-lasting effect; the benefits of a single dressing can last for 3 or more years.

Using farmyard manure

If you have some ground ready when the manure comes in, you will lose less of your manure by digging it in right away; but it is often a question of getting a load when you can and storing it until the ground becomes vacant. If you buy a ton of manure now, you will only have about a ton in six months time because the microbes change parts of the manure into carbon dioxide and ammonia gases which blow away in the wind; nutrients are also washed out of the manure during heavy rain, forming the brown liquid which you often see round the bottom of a dung heap.

While in the heap it is best kept under cover and always kept trodden down tightly to exclude air, and if the drainings can be collected in a bucket or tank a great waste of precious plant nutrients can be avoided.

In very dry weather, moisten the heap periodically. By stacking fresh manure straight from the stable or piggery for a few months the product is improved; you get a better balance in nutrient content, the nitrogen part becomes slower-acting and is less likely to burn seedlings or the delicate roots of tender plants. The well-rotted manure is much easier to spread and mix in with the topsoil. You can tell if it is well rotted by the absence of unpleasant smell and even texture of the product —the straw part will no longer be recognisable. Fresh manure is much more difficult to spread and mix; if you intend to sow or plant soon after an application you have to bury it deeply otherwise it interferes with operations needed for preparing a plant bed.

Deeply buried manure does not give the best results; ideally it is spread on well-broken soil and then worked in to a depth of 3 to 4 inches with a cultivator, then turned with a spade or fork. Take care not to turn the soil completely upside down, but rather at an angle wide enough just to cover the surface material. Manure covered with slabs of wet soil merely prevents humus formation. By mixing it with 3 or 4 inches of topsoil, hard crusts which prevent seedlings from pushing through easily, are obviated. To do any real good to soil that is low in humus it is essential to cover the soil with a layer thick enough to obscure the soil beneath it; this will need at least 10 lb of well-rotted manure per square yard. For vegetables this is done every 3 years before you plant crops such as brassicas that respond to generous dressings of manure.

Well-rotted farmyard manure can be applied at any time of the year before sowing or planting, but fresh or ‘long’ manure as it is called, is best dug in during the autumn or early winter so as to allow it to break down and lose its caustic nature in time for spring plantings.

For mulching during the summer the manure is useful for suppressing weeds and retaining moisture; when dug in at the end of the season it adds to the humus content of the soil.

Since large dressings of farmyard manure supply appreciable amounts of plant nutrients you can reduce your fertiliser dressings by half if 10 lb of well-rotted farmyard manure per square yard has been added.

Composted manures

There are a number of products derived from fresh animal manures that are sold in bags under brand names. Large heaps of the fresh manure are allowed to decay under cover for several months during which time the coarse material is broken down and the heat of decomposition drives off much of the moisture.

The resultant dark brown spongy manure is applied at the rate of 6 to 8 ounces per square yard and is lightly forked in or mixed with the topsoil by means of a rotary cultivator.

These products are clean and convenient to handle.


Compost is the term used to describe partially decomposed or pre-digested organic residues. Composting is done before adding organic materials to the surface of the soil as a mulch or mixing with the soil as a manure.

It might be thought that since humus is such a good thing and is made from organic matter, any kind of organic matter will improve the soil and will obviously give better plants, but this is not always true. Fresh straw, for example, when dug in without the addition of anything else, gives poorer plants not better ones.

In most organic manures there are two common substances —carbon and nitrogen —and both are necessary for humus formation. But straw has a great deal of carbon and very little nitrogen and when this is dug in, the soil microbes which are the humus makers take from the soil the nitrogen that they need for building up their own tissues thus robbing the plants of their requirements. If we add a nitrogen-rich material to the straw this will balance the carbon in the straw and so satisfy the soil microbes.

Other materials contain fairly large amounts of nitrogen and often decompose so quickly that much of the nitrogen and other plant foods are released so quickly that they are often lost before they can be used by the plants.

By combining such variable materials in the compost heap a good product can be obtained and better results achieved than if either kind of material had been used alone.

Well-made compost is equal in value to farmyard manure, but whether your compost heap is a useful source of humus or merely an evil-smelling rubbish dump depends on an elementary knowledge of the process of decay.

A common method of composting that has been practiced since ancient times is a slow process taking up to two years in which the refuse is put into a pit dug in the ground. The decay is brought about by anaerobic bacteria, that is, those that work in the absence of oxygen. Besides being inefficient, it produces evil odours, particularly when the heap is disturbed.

Good modern composting depends on organisms that require plenty of oxygen, known as aerobic bacteria, in order to break down the material quickly without objectionable odours. These are widely distributed in nature and are found in dust and all kinds of refuse so there is no need to add them. If you give them the right materials and their simple needs, air, moisture and warmth, they will do their work efficiently.

Raw materials

The soft sappy garden wastes such as lawn mowings, hedge and bank trimmings, weeds and vegetable leaves are ideal. Tea leaves, coffee grounds, eggshells and potato peelings and other kitchen wastes can be added. Less desirable are wood shavings, sawdust, tree bark; these are best composted on their own. Even newspapers that have been thoroughly soaked in water can be used.

Best kept out are thick woody stems, tough weeds and diseased plants.

Making the compost heap starting a compost heap

The area should be marked out on a well-drained site; it should never stand in a puddle. But it should be within reach of the hosepipe.

The size of the heap depends upon the amount of material available. You will need very large amounts of material to complete even a small heap in one operation, and you have to plan the size by the amount you have available.

As a general guide for a small garden an area 3 feet by 3 feet should be marked out in a well-drained and sheltered spot away from the house. Making the heap will be much easier if you knock in a stout stake at each corner. Then lay a layer of coarse material such as old prunings, broken up cabbage stalks to help aeration and drainage. Garden refuse should be mixed as thoroughly as possible so that the coarse waste is incorporated with the soft waste; this applies particularly to grass mowings which should not be put in thick layers otherwise air entry will be blocked. Cabbage stalks and woody herbaceous stems will rot quicker if broken up and chopped into short lengths before mixing with the softer material.

The heap is then built up layer by layer to a height of 4 feet, each layer being made 1 foot thick and compacted by treading or with a spade until it goes down to 6 or 8 inches. Each layer should be sprinkled with water; dryness is fatal, but never over-wet the heap, particularly during the winter when sodden conditions prevent bacterial activity.

The heap should have straight sides and the top left flat, or with a slight depression in the middle to catch and hold the rain.

It is much more convenient to make a bottomless bin of old planking or heavy gauge wire netting in which the waste can be collected and raked level. Extra stout gauge wire, galvanised, painted or plastic coated bins 3 feet by 3 feet hold one cubic yard of firmed material; when well-rotted the material in a bin of this size weighs about ton.

If the material is very woody or mature sprinkle sulphate of ammonia on each layer at the rate of ounce per square yard and water it in, otherwise special aids are unnecessary; good composting depends on maintaining correct conditions for the organisms that do the work I.e. moisture, air, warmth.

It takes about 6 months to produce good compost, but if you are in a hurry to use it you can get quite good compost in about 3 months, but turning the heap will be necessary to speed up decomposition. Heaps of coarse or woody material would have to be turned three times to speed up decay. A really wet heap would have to be turned more frequently; should there be a bad smell, a good rule is to turn the heap daily until the smell disappears. When turning the heap, always put the drier, outside material into the centre of the new heap.

The temperature of properly managed compost rises quickly even in cool weather as a result of the intense activity of the organisms and it may rise high enough to kill the weed seeds and spores of disease fungi. But there is no guarantee that they will all be killed so it is best to keep diseased material out of the heap.

You can tell when the compost is ready for use by extracting a sample from the middle of the heap with a trowel. It should be fibrous and break into small pieces when squeezed, be a dark brown colour and have a pleasant smell.

Using the compost

Well-made composts from vegetable wastes may contain more nutrients and more organic matter than good farmyard manure.


Fertilisers provide plants with the foods that they need for healthy and productive growth. They are commonly listed in catalogues under:

  • Straight fertilisers
  • Compound fertilisers
  • Liquid fertilisers

Straight fertilisers

These are used to supply a specific nutrient. If you wish to make your spring cabbages grow away more quickly in the spring you could top-dress with Nitro-chalk. If your tomatoes are not ripening quickly enough in dull weather sulphate of potash could help. Straight fertilisers are either in-organic `artificials’ or ‘organics’.

Artificials, which may be manufactured in factories, or are the purified salts from natural underground deposits, are more correctly known as inorganic fertilisers. They generally dissolve easily in water and when applied to moist soils act quickly. But this does not mean that they will be washed out of your soil. Both phosphates and potash are absorbed by soil constituents and so is nitrogen when applied as ammonium fertilisers. Nitrates, however, may be lost from the soil if applied during the winter or too far away from plant roots. Hence the need for top dressings.

Most inorganic fertilisers are fairly concentrated and we know exactly how much of each nutrient is present in any weight of fertiliser and so you can calculate how much fertiliser to apply to the soil to provide a desired quantity of any particular nutrient. But great care must be taken in handling them because being concentrated, overdoses are often harmful.

‘Organics’ are of animal or vegetable origin and their nutrients are locked away inside the complex structure of proteins and other materials. They must break down into soluble forms—nitrates or in some instances ammonia—before they can be used by plants. Since bacteria and other living organisms in the soil break these down, their effectiveness largely depends upon the soil conditions being satisfactory for the organisms; they are most effective when used in moist, well-aerated, well-limed soils. Many are fairly concentrated, but their nutrient content often varies from batch to batch.

Fine dusty particles break down much more quickly than the coarse fragments in organic fertilisers. For example a fine grade of hoof-and-horn meal works very nearly as quickly as some inorganic fertilisers, while coarse particles break down slowly and release their nitrogen over a long period of time.

Synthetic organics such as Urea-Form are chemical combinations of urea and formaldehyde and are designed to give a slow release of nitrogen for several months. Their granules are almost insoluble and do not break down in the soil. The outer surface of each granule is gradually worn away in much the same way as you would suck a sweet. The process begins within a few days in warm moist soils and continues to release nutrients as the plants need them for long predetermined periods. So, a `one-shot’ application may nourish plants throughout the growing season, whereas several applications of quickly available forms may be necessary.

Fruits and vegetables, properly fertilised with quickly available forms of nutrients are as healthful and tasty as those fertilised with slowly available forms ; plants obtain their nutrients as simple chemicals through the roots. And these chemicals are exactly the same whether they come from an ‘artificial’ or an `organic’ fertiliser.

Compound fertilisers

These contain two, or more usually, all three of the major nutrients nitrogen, phosphorus and potassium. These are the ones that are used by plants in the largest amounts and are, therefore, most likely to be deficient in soils. When you buy a fertiliser, therefore, you generally buy it for its content of these nutrients in order to give a balanced feed before sowing or planting.

Ready for use compounds Garden supply shops offer for sale a wide variety of materials for feeding garden plants and lawns. Some of these products are much more expensive than others.

Fertilisers with a high percentage of plant nutrients cost more per pound than those containing a small percentage of nutrients. So always find out from the supplier what the guaranteed content of nitrogen phosphoric acid and potash is. The plant nutrient content of a compound is often indicated by its grade— a series of three numbers separated by dashes. The numbers show the percentage of nitrogen, phosphoric acid and potash, in that order, contained in the product.

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