THE USES OF LIME

New Zealand Herald, Volume LXIX, Issue 21328, 1 November 1932, Page 16

THE USES OF LIME

EFFECT ON FERTILITY TIME OF APPLICATION BY R. .A. S. CANTRELL No general rule can lie laid down as to the best method of utilising the elements of plant food which a soil may possess. It is true, that all plants draw from the soil, in a soluble form, the same elements of plant food (phosphorus, potassium, nitrogen, calcium, (sulphur, iron) and that all annuals need the same food materials, classified as proteins, carbohydrates, fats and minerals, in their rations, but these facts do not justify the conclusion that the same plant food, or fertiliser, will prove satisfactory for all kinds of crops. The fertility of a soil must be interpreted in terms of the crop to be grown, the amount of plant food in the soil, the tillage practised to make that plant food available and the climatic conditions. It is recognised that of the essential constituents of the food which cultivated plants obtain from the soil, those which aro liable to become temporarily exhausted, include nitrogen, phosphoric acid, potash and lime. The last-mentioned constituent is not generally recognised in itself as a manure, but rather as a releaser or preparing agent of soluble plantfood constituents. Any soil that contains less than 1 per cent of carbonate of lime can be improved by liming, and any soil containing less than .2 per cent, cannot make proper use of the fertilisers applied. Ground Versus Carbonate One often hears practical farmers extol the merits of burnt lime (caustic) and disparage the value of carbonate of lime (ground limestone). The point depends upon the condition and type of land under view. On soils well supplied with humus (organic decaying matter), burnt lime may, generally speaking, be used with impunity and considerable advantage. On light lands, however, it is advisable to use carbonate of lime. Of course, there is no harm in using burnt lime in quantity on light lands, if the humus supply is maintained, but few farmers appear to bother about this necessary operation, for the simple reason that there is a lack of appreciation of its merits. When cartage or railage- is a matter of moment, there is no doubt it is wiser to use the burnt lime, as 561b". of burnt lime is the equivalent of some 1001b. of carbonate. Certainly one should use the burnt lime, if over the free limit on the railway of 100 miles. When and how to apply lime to soils is a debatable point among farmers. It is customary in Otago and Southland to lime in the autumn and early winter, on the ploughed land, in order to permit of subsequent mixing with the soil, prior to sowing some crop in the spring, when usually one sees good results. The rains of winter wash the lime into the soil, and it is well distributed by harrowing. The rate at which lime should be applied to land*depends upon the soil and climate. Treating Acid Soils It is probable that one cannot, in practice, apply too much limestone to acid soils, and generally speaking, it is quite safe to apply one to two tons of finely divided carbonate per acre, compared with say lOcwt. to 15cwt. of ground-burnt lime per acre. Then too, the carbonate is infinitely easier to handle than burnt lime, while there is no danger in haulage or in storage, if tho material gets wet. It is generally recognised that lime sweetens the soil, and makes it easier to work, always provided tho drainage is adequate, while the fact that plants are enabled to make good use of any artificial manures applied with the crop on limed land, should not be over-looked. Many parasitic organisms which cause losses among farm crops thrive in tho absence of lime, while limed land is generally recognised as yielding amplo nutritious grasses and clovers.