Pasture Plants And Their Mineral Content

Sun (Auckland), Volume III, Issue 768, 14 September 1929, Page 31

Pasture Plants And Their Mineral Content

THE EFFECT OF FERTILISERS

RECENT INVESTIGATIONS into stock health and thriftinesfi in ;he Dominion have brought into prominence the important part played by the mineral content of the leaves of pasture plants on which the stock has been grazing. The influence of application of fertilisers upon the mineral content of lucerne has been subjected to close research by Mr B. W. Doak, M.Sc., at the Cawthron Institute, and a brief review of his conclusions are given hereunder.

To ascertain the effect of manures jpoo the mineral content of the leaves lucerne an area was subdivided into plots treated with applications of four fertilisers:—(a) Super and lime, (b) super potash and lime, (c) super and potash, and (d) lime alone. A control plot was reserved for comparison purposes. The lucerne grown on these plots was subjected to chemical analysis as well as weighing tests. The •pplication of super potash and lime produced the greatest weight increase. The control area yielded at the rate of 53cwt an acre, while this special mixture gave a yield of 85cwt. Lime by itself depressed the yield, hut in all cases where lime was applied »t increased the lime content of the leaves by some 12 per cent. Naturally * amount was therefore available for stock grazing upon it. >uperphosphate increased the phosphoric acid, sulphur, and potash content of the ash, ut these increases * er fi T 01 *? ma rked whenever lime was applied with the super. Lime similarly helped sulphate of potash to increase the potash content of the lucerne. Chemical analysis of the pastures the two plots to which both super and potash were applied reJk* m that the addition of lime was shown to a marked extent in the influence it exerted ®P°n the absorption of other •Inerala. The amounts of the calcium, Phosphoric acid, potash, I!ii i* n * n d "ulphur present were larreased, the increase being ery marked in the case of nitrogen.

showed the heavy an]„a toll taken from the soil by the cro P* From the area treated ,I, T e ’ super phosphate and sulE. ® , of potash 85ewt of hay an acre This meant the removal acre time equivalent to carbonate of lime, of phosphoric ii suc h as would he supplied by 2461 b val«».» SU * pcr «l >^osphate : of potash equisnd of sulphate of potash, n i 6 Yu sulphur. Therefore, to re?P9le the annual removal of the mina lucerne field giving this oi nay would require a ton-dress-

iug of three and a-half cwt of carbonate of lime, two and a-quarter of iuper phosphate, two and three-quarter «wt of potash, and almost hall a cwt of sulphur an acre. Mr Doak’s analysis showed that the mineral content of lucerne was greatly affected by the seasonal conditions prevailing prior to the examinations made. In autumn, under normal conditions the lime and phosphate percentage* fal. off appreciably, the phosphate fail being greater in dry weather. In dryweather, however, the lime percentage increases, and in all cases the percentages of potash and lime present varies inversely. In view' of the prevalent idea of the superiority of lucerne as a feed for growing animals and milking cows, ana. lyses of the young growing shoots of lucerne and of average Nelson pasture grasses were made. It was found that the young green growth from the pastures resembled very closely lucerne in its content of crude protein and nitrogen free extractives. The percentage of lime in the lucerne, however, was more than double that in the young pasture, while the lucerne was also superior in sulphur content. On the other hand, the young pasture was fou* times as rich as the lucerne in chloiine, and also contained more potash and soda. It has usually been considered that young lucerne owes its superiority over grass to its high protein content, blit under New' Zealand conditions it would appear that the protein content of prooerly treated grass pasture is remarkably high and that the lead of lucerne in this respect has not been '.r aintained. Mr Doak’s experiments emphasise the fact that the mineral content of the lucerne plot may _be profoundly affected by the application of fertilisers and that the weather also exerted considerable influence. The superiority of the lime content of lucerne, however, will always make it valuable toward improving the lime balance of a ration deficient in. this essential element of animal nutrition.