LIME LIBERATES PLANT FOOD.

Hawke's Bay Tribune, Volume XIX, Issue 220, 4 September 1929, Page 8

LIME LIBERATES PLANT FOOD.

Besides correcting acidity in the soil, lime acts on the inert humus, liberating the nitrogen from this, and also on the insoluble mineral potash in the soil, making this available to the plants. Further, it acts on clay soils by making them more pliable and easily penetrated by water, air and plant roots. It also produces conditions favourable to the multiplication of soil bacteria, for these cannot thrive in an acid soil, and through the work of the soil-bacteria a vast amount of plant food is laberated from otherwise insoluble matter. Because of its effect in rapidly making humds soluble, quicklime applied to porous soil deficient in humus will stimulate immediate growth, but will ultimately impoverish these. In effect, 56 lbs of quicklime is equal to 74 lbs of slaked lime, or 100 lbs of limestone, hence, apart from the cost of haulage, limestone is cheapest (and safest) unless it costs more than half as much as quicklime, an unusual occurrence. The writer has always thought that much more use might be made of the outcrops of lime which occur throughout the North Island by farmers combining to erect suitable co-operative crushing plants at centrally situated outcrops. SALT, SALTPETER AND GYPSUM:. Salt, saltpeter and gypsum are “amendments” which act on the potash salts in the soil, making them more rapidly available. Salt and saltpeter have been largely used in the past on almost all crops, including grass, and where potash is lacking in an available form, have resulted in greatly increased crops. By the application of 5 cwt. of salt per acre test crops of mangels have been increased from 27 to 35 tons per acre, while the results with wheat and other cereals has bee nequally marked. Pasture top-dressing with from 5 to 10 cwt. of salt has increased from 50 to 100 per cent, in carrying capacity, while the stock have been much more healthy and free from parasite infection. It must be remembered however that heavy application of salt or salt peter cannot be continued without ultimately seriously damaging the fertility of the soil. At frequent -intervals, and in inoderate ap-

plications salt is a wonderful growth stimulator. Gypsum, (calcium sulphate), may also be used as a potash liberator. Crops such as turnips, mustard, rape, cabbages etc. which benefit from a supply of sulphur will secure some of this requirement from gypsum, but its main direction is in making available the potash reserves in the soil.