MANURES AND FERTILISERS

Otago Daily Times, Issue 21580, 27 February 1932, Page 19

MANURES AND FERTILISERS

A FEW IMPORTANT FACTS Good gardeners should never forget the original meaning of the word manure. It really signifies “to work by hand, and in olden times the word was used ™ denote hand cultivation. In these days when the word has taken to itself a quite different meaning, one should bear in mind that no application of fertilising material 'is of any use without work in the form of systematic trenching ana subsequent hoeing. . . , . There are three essential things necessary to all plant life—air, water, and certain mineral salts. When a plant is burnt, the bulk of the material disappears, leaving behind a relatively small amount of ash. The portion which burned away was practically all obtained air and water, and the ash represents the mineral salts which were taken from .the soil. Many years ago, before the subject was understood, it was thought that the ash, the composition of whiqh varies from plant to plant, represented just what that particular subject needed for its growth, and nothing else. Much time was wasted in the analysis of these ashes and the tabulation of the results. It is now known that the composition of the ash depends largely upon what the plant found in the soil. In other words, it is much like ourselves; what we eat at a meal depends on what is in the larder, and it does not necessarily follow that this is the best food for our health. Before we consider the nature of plant foods, it may be well to emphasise one other point about “ manure,” with its oldfashioned meaning. The mineral salts which are, or should be, in the soil, must be in a form suited to the plant’s method of absorption, just as our own food has to be suitably prepared. It is only in recent years that it has been discovered that a plant cannot absorb its food from the soil unless micro-organisms are present which will facilitate the process. In other words, the soil, if it is fertile, is alive, and must be treated as a living thing. This invisible living population of the soil needs air like the rest. of us, and thus it is only the upper layer of the soil which is normally alive. In deep trenching, therefore, it is fundamentally wrong to bring up to the top the lowest spit of soil, because the chances are that it has been down there in a compressed state without air for a Jong time, and is dead. If it is brought to the top, it must be allowed to “weather”; that is,_ time must be given for the micro-organisms to multiply and spread to the newly aerated soil, and thus make it fertile. In order that these beneficent organisms may thrive, it is necessary that the soil contains decayed vegetable matter, which gardeners call humus. When vegetable matter decays, it tends to generate a weak acid, and the soil is then sour. No successful gardening is possible in a sour soil, and it is a waste of time and material to apply a fertiliser to it until the acid has been neutralised, and the soil is in the conditions which gardeners, call “sweet.” This is best accomplished by means of lime or chalk. The beneficial effects of liming the soil have been appreciated for centuries, and its importance (in the case of soils which need it) cannot be over-stressed. There are certain indications of a sour soil which should never be disregarded. In lawns a matted skin under the grass; “finger and toe” disease in turnips; the prevalence of certain weeds, such as spurry and sorrel; excessive stickiness in clay soils, and a general tendency for plants to “go off ” just before reaching maturity. The most positive test, however, is to take a handful of soil from various parts of the garden, mix them together, and put sufficient of the mixture into a glass jam jar to half-fill it. Then pour a couple of ounces of spirit of salt into the jar. If the soil effervesces (fizzes) freely, all is well; if not, it is undoubtedly sour, and needs liming. THE IMPORTANCE OF LIME, There are many forms of lime and chalk which can be used for this purpose, and farmers who have many acres of land to treat have to consider cost and efficiency with some care. But for the average gardener, slaked lime, supplied by horticultural stores, is safe and effective. “ Quick ” lime, used by builders, should not be employed, unless the ground can be left to weather for some months before planting takes place. The iime used should be friable, and it is best applied when ,the soil is relatively dry, and hoed in at once. If this is done on a fine autumn day, the winter rains will wash it into tlje soil, which will then be in good condition for the spring. Lime may, however, be applied at any time during the winter and early spring when the ground is not too wet. If a dressing is given to a lawn, it is desirable to do so during the winter, as a spring dressing is liable to retard the early growth of grass. Lime used for this purpose should be in. a wellpowdered condition, and, if rain does „not soon follow the dressing, it is a good plan to hose it in. On soil which is very sour'as much as 21b of lime per square yard may be applied although this amount should not be exceeded. Usually half this amount would be a sufficient dressing, and, after the soil is brought into condition, it is a wise plan to give a dressing of about a quarter to half a pound ner square yard once every five years. Lime is a fertiliser in itself, and it is an absolute necessity for the effective action of other fertilisers. As it is slightly soluble in water, it is slowly washed out of the soil. In addition, all plants absorb a certain amount of lime salts, and thus it is seen that the soil must have its lime content replenished from time to time. Since stable manure has been largely replaced by chemical fertilisers, garden soils arc often deficient in humus. This can readily be made good by rotting down all leaves, lawn mowings, soft weeds, and plants, and returning the product to the soil. It is a good plan to make a heap of this material during autumn. — A. H. S., in Amateur Gardening.