Garden Tips

The addition of manures to the soil so that it can be cropped continuously has been practiced for thousands of years, and the more densely populated the country the more has the value of organic manures been appreciated. These organic manures are derived from animals or vegetables, and all contain a wide range of chemicals which plants require in a form acceptable to them. The great advantage in using organic manures is that not only do they contain a readily available supply of plant food, but they also have a profound effect on the structure of the soil itself.

Let us take as an example a sandy soil where individual soil particles are large and do not join together. Here drainage will be very rapid and plant foods will easily be washed down below the reach of the plant roots. If some of these particles of sand could be joined together, drainage would not take place so rapidly, and this is what organic manures can do. They join particles together and so assist in producing larger ‘crumbs’ of soil; this assists water to rise in the soil and at the same time decreases the speed with which rain water will soak away.

With few exceptions, most garden plants respond to the application of manures, but higher yields alone can be obtained by other means. Organic manures improve the texture of the soil and raise the humus content. Humus is decayed vegetable matter in the soil and a soil of high humus content is usually referred to as ‘black soil’.

Organic manures are generally in short supply in the tropics, but even those that are fairly easily available are often ignored or wasted. The most popular organic manure is compost, but the dung of horses, cows, sheep, goats and poultry, together with dried blood and bones, should not be overlooked. The merits of each are summarised below.

HORSE AND COW MANURE: Where this is available locally, it should be used in preference to all other manures as it is a complete manure and will improve any land. Horse manure, if obtained from stables, should contain plenty of straw which, when rotted down, will become perfect humus. Horse manure should never be used when fresh as the ammonia salts in it will burn the roots of young plants. If stacked and covered for a few months it will become quite harmless. Covering is essential as the ammonia salts are available in a very soluble form and can easily be washed away. Cow manure is not dangerous when fresh and may be applied either on top of the soil or dug in.

SHEEP AND GOAT MANURE: Both are particularly valuable for use when preparing the soil before planting. If stored, they must be kept covered, or the nitrogen, which is in the form of ammonium salts, will be lost through leaching.

POULTRY MANURE: Again a manure high in nitrogen, poultry manure makes its nitrogen available very quickly instead of over a period of weeks or months. For this reason it can be of great value for crops requiring a lot of nitrogen at a particular time. Poultry manure does not keep well and is often mixed with rather undesirable litter from the poultry pens, which makes it the least useful compared to others.

BLOOD MEAL AND DRIED BLOOD: These may be available from the local slaughterhouse and, if cheap, are well worth buying. They are particularly high in nitrogen, but contain so many other plant foods that they can be used as a top dressing for pot plants. As dried blood absorbs water very easily and by so doing disperses some of its nitrogen, it should always be stored in tins or boxes away from damp.

CRUSHED BONES: Of particular value to the tropical gardener as they contain a high percentage of phosphorus which is gradually made available over a long period. If incorporated in the soil before planting shrubs, they will provide a satisfactory source of phosphorus. Other forms of bones, such as bone flour, provide a quickly available source of phosphorus, and are normally used only as a top dressing where this chemical is required at a particular time. Fresh bones should be covered with earth and kept wet, before they are smashed up. In this way the phosphorus will be more readily available when they are used.

FISH WASTE AND FIsH MEAL: Both can be dug into the soil and will provide a good supply of readily available nitrogen and some phosphorus. Fish waste should always be buried immediately to stop noxious smells.

SEAWEED: Seaweed should be used in coastal areas where it is available, as it contains a high percentage of potash and lime. It should be dug in before planting, as in this way it not only provides a valuable source of a wide range of plant nutrients, but also rots down to produce humus. It can be used after the salt has been allowed to leads out.

COMPOST: The importance of compost cannot be overstressed. Often it is the only form of organic manure available to the gardener, particularly those living in or near towns. It should be a matter of principle that no vegetable matter is burnt but retained for compost, with the exception of very woody prunings and diseased material. The best compost is made from young, succulent growth, as this part of the plant contains an abundance of valuable chemicals. Grass cuttings, hedge trimmings and waste from the kitchen can be turned into compost very much more quickly than morefibrous older material. Cabbage stalks are not particularly useful and should be burned. There are several ways of making compost, but all employ the same principle – the breaking down of fresh herbage into a dark- colored crumbly material by the action of fungi and bacteria.

Compost can either be made in trenches below ground level, or in heaps above the ground; the latter is more suitable in high rainfall areas as trenched material gets too wet and the process is prolonged. Whichever method is used, siting should be given careful consideration. Ideally, compost should be made in a secluded corner of the garden where it cannot be an eyesore, and also at a high point so that the area cannot become waterlogged. Other factors to be considered are distance from a water supply (as it will need watering during the dry season) and distance from where it is to be used.

Having compromised on the site, the compost can now be made. If the trench method is used – and this is usually the best method for an ordinary sized garden – five shallow pits should be dug, not more than 4 feet square and 6 inches deep. If the garden is small, then the pits can be less than 4 feet square.

Place in the first trench grass cuttings, weeds, hedge cuttings, leaves, in fact anything that will rot down quickly. Use grass to make the sides of the trench into a wall, laying it along as if making a wall. When the walls are made there will be a lower part in the centre. Into this can go kitchen waste, such as potato or yam peelings, the rinds of fruit, and any rotten fruit, such as mangoes, which may be about. Always cover these materials immediately with either fresh grass or earth so that flies cannot get at the rotting material and make a breeding ground of it. If no fruit or peelings are available, animal manure may be used and will give the same result. Failing this, use the richest darkest soil in the compound.

These materials in the centre of the pit are known as ‘starters’ as they contain some of the valuable bacteria which will attack the other herbage and split the cellulose it contains, ultimately turning it into compost. These cellulose-splitting bacteria need air, moisture and warmth to enable them to do their work quickly and efficiently, so the compost pit must get air, even at the bottom; and in dry weather water must be applied. If this is not done, little change will take place in the materials.

There are other chemicals which will help to turn herbage into compost; these do not actually contain bacteria, but they will induce a chemical action in which bacteria can thrive. Sulphate of ammonia is one, and there are others sold commercially under trade names. These chemicals are known as ‘activators’.