SOIL AND PASTURES

New Zealand Herald, Volume LXXI, Issue 21793, 7 May 1934, Page 15

SOIL AND PASTURES

MINERALS FOR LIVESTOCK

HEALTH AND DEVELOPMENT

BY H.H.T,

Tho lowest forms of " life " are tho multitudinous soii bacteria. These live in a medium of mineral and vegetable matter—i.e., tho surface soil —wliero they breed, live thoir short and useful life and die. ft is estimated that in averagely fertile soil thero are millions of these infinitely small animals, if they can bo called such, to tho square inch. There aro countless varieties of bacteria, but in tho main their duties appear to be the same—tho conversion of inorganic into organic matter. Their food is principally the finely-divided mineral matter in the soil and various elements, such as nitrogen, oxygen, carbon, etc., which they extract from tho air that penetrates the surface soil. \\ ithout them soil is barren, for the plants aro dependent largely upon the organic matter which —in life and death—these bacteria produce.

As lifo takes on higher forms, as in trees, shrubs, grass, birds, herbivorous animals, etc., it requires an over greater proportion of its mineral food in organic form. At the same time all species of life, right up to man, retain tho ability to absorb some inorganic minerals direct into the system, and that which they may consume and cannot absorb is converted, through tho digestive acids, into a solublo form. This, in the form of manure, is more readily available as food to bacteria, insects and plants than in its original insoluble state. Mineral Eequiramenta The amount of minerals in either form—inorganic or organic—necessary to maintain growth and health is greater in the lower, or more-quickly developing species of animal and plant life, than in the longer-lived and more slowly-developing species, and is required in greatest quantity by tho young of all animals, both before birth and during tho period of growth. The amount of minerals required to promote healthy growth and reproduction in any species is discovered by analysing the milk. Tho ash content of tho milk represents the inorganic minerals which tho young; of the species require, and from tho following table, which is a modification of that drawn up by Proseher and Abderhalclen, it is clearly demonstrated that where the rate of growth is rapid tho mineral supply must be correspondingly high:— Time takc.i tc Ash content double weight of milk of after biri.i. aperies. Man . . . 180 days 0.25 p.c. Cow .... 47 " 0.72 " PiK .... 14 " 1.03 " Rabbit . . 8 " ".50 "

In accordance with tho goneral law that the faster the rate of growth the richer must the food be in constructive material required for bone and soft tissue formation, mineral-rich pastures will support rapidly-growing animals in health, whereas mineral-poor pastures will support only animals with a slow rate of growth. Where the mineral content of a pasture becomes depleted below the point required to maintain the mineral proportion in the dam's milk, the result is, first, a slower rate of growth in the young, then a quick decline in the birth rate, accompanied by a higher rate of mortality in the young, and, finally, the disappearance through death of the particular, species from that area. Examples of Deficiency Examples of mineral deficiency having this effect are common in tho North Island. Where once rabbits were a pest and appeared to thrive on the scantiest feed, they have now entirely disappeared, despite much more abundant grass growth. On these areas sheep ■farmers at one time had little difficulty in securing a good lambing percentage and strong-growing young ewes which were ready to put to the ram as twotooths. To-day tho grazier on these areas thinks himself lucky if he can dock £0 per cent of lambs, and these youngsters are so slow-growing that thoy are not fit to be put with the ram until they are four-tooths. In general, the poorer the pastures arc in mineral matter the lower the carrying capacity, the slower the rate of growth of the young animals and the higher the incidence of disease. Different species of grasses, like different species of animals, require minerals in varying quantity. Some soils will grow to perfection only such grasses as danthonia, Chewings' fescue, or others having a low mineral requirement, and these pastures will carry only small-framed breeds of sheep having a slow rate of development. When the mineral content of the soil is raised, as with topdrcssing, superior grasses having a higher mineral requirement soon make their appearance, and carrying capacity, lambing percentage, rate of growth, size and mortality rate are all rapidly improved.

The volcanic areas of New Zealand are particularly deficient in some of the most important mineral elements, and in particular in lime, suit, phosphorus and iodine, a shortage of any one of which may become the limiting factor for either growtli or health. This is accounted for partly because the soil of these areas lias in the past been deficient in humus, and therefore in bacterial life, with the consequence that organic: minerals have not been made available, and largely because there wore no largo herbivorous animals to aid in the conversion of inorganic to organic, or at least soluble, minerals, and to distribute supplies of bacterial and plant foods. Part Played by Animals

The part played by animals—particularly the herbivorous species—in building up the mineral content and fertility of the soil is important to the grazier. Although animals can assimilate only a comparatively sma.il quantity—varying with the species—of inorganic minerals, and can therefrom only to a limited extent make up any organic mineral deficiency in the pasture, they convert any excess of minerals which they may cat into a highly-soluble form and distribute this oxer the pasture. The action of the digestive organs and gastric juices converts many of the insoluble and therefore useless minerals into a soluble form, much in the same manner as we convert rock phosphate into superphosphate by chemical processes, and, mixed with fragments of humus in the dung, this forms a perfect medium for the development of beneficent soil bacteria. Nature has provided herbivorous animals with an abnormally large appetite for minerals and mineral salts, and provided they have a plentiful supply they act as both manufacturers and distributors of essential mineral plant food. Because of natural mineral shortage, accentuated by the export of onprimary products, animals in the North Island have n tendency to become smaller and less prolific. This does not apply along the coast where, in many instances, the land is formed of ancient sea-bed which has been thrust up by earthquake or other upheaval, and contains abundance of lime, phosphate and other organic minerals, the product of fish-remains-. This land still grows healthy and prolific stock, although the fact that supplies are not inexhaustible is demonstrated by the response much of it makes to phosphatic dressings.