THE RURAL WORLD.

King Country Chronicle, Volume VI, Issue 509, 16 October 1912, Page 6

THE RURAL WORLD.

PLANT FOOD AND DISEASE. It has oftan been pointed out that herbage grown upon soil well supplied with'phosphate of lime supplies a food far more healthy and strengthening than poor, neglected pasture Agricultural literature contains examples of wide districts where the stock within the last 20 years has improved almost beyond recognition, in consequence of the pastures and haylands being enriched by dressings of mineral fertilisers. Here is another similar instance that has just come to our notice. A disease calied "stiff-sick-ness" in cattle attacks a number of cattle in Africa. It is something like lilaminitis in horses. The acting director of veterinary research has been investigating the cause of the malady and thinks it is due to the want of phosphates in the food. Thus he writes: —"In this disease the enzootic influence is, in my opinion, a pecuilarity of the soil which, in dry seasons, becomes incapable of supplying all the ingredients in their proper proportion which constitute a complete plant food. The soil may and does contain all the necessary constituents of plant food, but they exists in an unavailable form. There is often a great quantity of fertilising matter in the soil, but not in a condition immediately available for th" growth of plants. • Thus phosphates exist often potentially in a dormant stata in the soil in great abundance, but it is not until they are of any use as food of plants. The phosphates are highly important in an agricultural point of view; unless they are present, no albumen or other azotised matter can be formed. Azotised matter cannot exist without the presence of phosphates."

LIGHT AND PLANTS. At a recent meeting of the Royal Horticultural Society of England, Professor Henslcw gave a lecture on "The Use of the Spectroscope in the Study of Plant Life." He treated hia suoject in a popular way, explaining that every portion of the sunlight, whether visible or invisible, is used in the production of a plant. ,Lettuce and ceandine were the two plant on which he had made his experiment. He had saved them by growing them under different coloured lights, thus denying them the benefit of certain parts of the spectrum. The processes were going on at all times in every green vegetable, and each was controlled by a definitely coloured light, if that colour was withheld a certain part of the nutrition went wrong. The absorption of carbonic aid and moisture from the air which produced starch in the leaf were entirely controlled b}? blue and yellow light. If this were cut off, as might easily be done by growing the plant under red glasß, no starch was formed. Transpiration, whcih was quite distinct from mere evaporation, was contiolled by reJ and violet rays. In green light a plant lost all its normal restraint, and evaporation took ' place so rapidly that it wilted and died. The third process, that of respiration, which supplied energy, was helped by red and infra-red. This explained why many seaweed which were expossed to the air during certain portions of the day were ; while all deep seaweeds, which existed in water which could only supply them with small quantities of oygen, were usually red. Thus o.ach part of the light which a plant was likely to receive had its own sphere of usefulness, dovetailing in with some other colour which produced different results.