GOOD FOR THE SOIL

Wairarapa Times-Age, 5 April 1940, Page 8

GOOD FOR THE SOIL

VALUE OF HUMUS. A great deal of interest has appeared lately in regard to the value of ‘■humus’’ and the part it plays in the growing and production of vegetables. It has almost been given the status of some new invention or new manure. However, to come down to facts, "humus” is that part of the soil which is organic and is formed by the breaking down or decay of animal and vegetable matter, by the aid of bacteria and other organisms. The value of "humus” has been known since time immemorial, and every soil in which will grow any of the flowering plants contains some proportion of humus. In other words, a soil entirely devoid of humus would only grow lichen and mosses. It is derived from the remains of vegetables and animals which have lived and died in or upon the soil, which have been spread over it by winds, rivers and rains, or which have been added by the hands of man for the purpose of increasing its natural fertility. This organic part varies very much in quantity in different soils. In some, as in peaty soils, it forms from 50 to 70 per cent of their whole weight; and even in rich, long, cultivated soils, it has been found, in a few rare cases, to amount to as much as 25 per cent. In general, however, it is present in much smaller proportion, even in our best arable lands, Oats and rye will grow upon a soil containing only 11 per cent, barley when 2 to 3 per cent are present, while good wheat soils generally contain from 4 to 8 per cent. The rich alluvial soil of the valley of the Nile contains only 5 per cent of dry organic matter. In stiff and very clayey soils 10 to 12 per cent is sometimes found. In very old pasture lands, and in gardens, vegetable matter occasionally accumulates so as to overload the upper soil. The comparative value of’peaty or boggy soils may be judged of from the fact that of the 5000 flowering plants of Central Europe only 300 grow on peaty or boggy soils, and these mostly belong to the rush and sedge families, useless to the farmer. Humus, when acted upon by acids and alkalis, yields ammonia and soluble nitrogen compounds. The percentage of nitrogen in a soil is. as a rule, in proportion to its organic matter; the more organic matter a soil contains the more nitrogen will be present. Of course there are exceptions to this rule. Feeding The Plants. Another influence of the organic portion of the soil, whether naturally formed in it or added to it as manure is not to be neglected. It contains —as all vegetable substances do—a considerable quantity of inorganic, that is, of saline and earthy matter, which is lib- . erated as the organic part decays. Thus living plants derive from the remains of former races, buried beneath the surface, a portion of that inorganic fo’od which can only be obtained from the soil, and which, if not thus directly supplied, must be sought for by lhe slow extension of their roots through a greater depth and breadth of the earth in which they grow.

The addition of manure to the soil, therefore, places within the easy reach of the roots not only organic but also inorganic food. It must be remembered, however, that the absolute amount of nitrogen in the soil no more determines its fertility than does the amount of mineral food it contains. In both cases a great deal depends on the condition of the nitrogen and mineral matter, i.e., as to whether it is in a condition available as plant food.

Preparing Humus. In days long past the chief source of supplying humus to our garden soils was by means of stable manure. This is now quite inadequate, except in a few cases, and in this country the supply of stable or. animal manure has never been equal to supplying the necessary amount required for the replenishing of our soils. In making up the lack, the question arises as to whether the supply of vegetable refuse and the correct preparation from a hygienic point of view is capable of supplying' the necessary requirements of the ordinary garden without the aid of so-called “artificial manures.” It is up to every gardener

to see that all vegetable refuse is returned to the soil. If possible, put this refuse into a so-called compost heap and let it be reduced by natural bacterial methods to a black soil-like mass. The addition of a layer of soil, sufficient moisture to keep the mass moist, but not wet, some organic matter, such as a portion of an old compost heap, stable, cow or sheep manure, or, failing any of these, add a dusting of sulphate of ammonia and superphosphates, these setting up a bacterial action which will hasten the process of decay and render the refuse suitable for plant food in three, instead of six, or even 12 months.