SOME ASPECTS OF LIMING.

Otago Witness, Issue 3594, 30 January 1923, Page 10

SOME ASPECTS OF LIMING.

Liming is probably one of the most important matters in respect to arable acres which confronts the farmer at this season of the year. We say arable acres, as, excepting newly-grassed lands (one to, say, three years old), it is not worth while liming pasture—unless, perhaps one should say, the intentifin is to plough immediately. A “limey” pasture ploughed up, cropped, cultivated, and in course of time again limed would no doubt be scientifically correct, and practical too, where lime is cheap. It is not the custom, however, nowadays to lime for the next generation. It never in this country a habit joi the Nomads who settled in New Zealand to think of the farmers who would come after them. Altruists are scarce in any country, so we cannot perhaps blame the pioneers who tilled our virgin acres. There comes a time, however, when it is easy to see that we are heading straight for lime bankruptcy. No amount of artificial manure can restore loss of fertility due to soil acidity. It is time the land was treated with lime in some form. It is a mistake to imagine that the use of artificial manures will do away with the necessity of liming, no matter whether we freely use basic superphosphate. The great number of soil analyses made by officers of the Department* of Agriculture clearly indicate that most of our soils are deficient in lime. Clover failures may be ascribed to acidity in many instances and a high'er lime requirement. Granted, then, that there is an obvious need for increased liming, it is as well to realise that “lime” for agricultural purposes may be obtained in at least three forms—viz., burned lime, ground quicklime, and ground limestone (carbonate). The last-named has been coming into favour of late years; but it has its limitations. Generally speaking, limestone, finely crushed, is effective in correcting sourness and in assisting chemical and bacterial actions, but is inferior to burned lime for improving the texture of heavy clay soils. Small applications of, say, up to scwt of crushed limestone per acre on stiff clay soils is merely playing with the liming question. Five times this quantity per acre is necessary, finely ground, and then “some.” Summarising the reasons why finely-ground limestone rather than burned lime may be used, we have (1) the high cost of fuel; (2) much finer grinding is practicable than was the case 10 or 15 years ago ; (3) it is possible now by laboratory methods to ascertain the lime requirements of soils and give the farmer an idea of the minimum quantity of limestone needed to meet the requirements of his particular soil; (4) in the case of soil with low lime requirement it is easier to apply small dressings of carbonate than of lump lime. In a general wav, it is safe to say that the finer the limestone (the quality being similar) the greater are its effects on the growth of leguminous plants. We have then conditions which in farming practice facilitate thorough incorporation with the soil particles—a very important matter, it will be admitted, when small quantities per acre are applied. Oue should not expect striking results from small dressings of carbonate on soils rich in organic matter, where there necessarily follows a high degree of acidity and initial high lime requirement. Such soils dissipate small dressings of lime before it can reach the underlying portion of

the soil—that is to say, on pasture land. Hence we may safely contend that small dressings of carbonate (limestone) on fairly well equipped humus pasture lands will show practically no results. Applied in large quantities, however, the results might well be satisfactory. In some general conclusions made in the Homeland on liming, with special reference to the uses of ground limestone (J. J. Griffiths, B.Sc., English Journal of Agriculture) it is stated : (1) Liming as a general farm practice must receive more attention if soil fertility is to be raised and food producction increased. (2) Great losses must be taking place in connection with the pasture laud of the country, because soils are deficient in lime when grass and clover seeds are sown. (3) In view of both the increased cost of fuel anti the improvements which have been effected in the construction of pulverisers and crushers, ground limestone may under many circumstances be advantageously taken as a substitute for burned lime. (4) A demand for ground limestone may lead to the opening up of disused quarries outside coal areas, and may thus establish new centres of distribution. (5) There appear to be various reasons whv expenditure on ground limestone has often been unremunerative in the past—viz. : (a) Coarseness of grinding; (b) more impure limestone used for its manufacture than was the case for the production of burned lime; (e) the smallness of the dressings which have often been applied to soils which needed fairly heavy liming • (d) the exorbitant prices which have on occasions been charged for it when the percentage of carbonate of lime has not apparently been as high as in the “lime" burnt. Just what changes lime or limestone (carbonate) effects upon the soil may be briefly stated. It hastens the decomposition of humus, promotes nitrification, helps nitrogen fixation in the legumes, remedies sourness in land given drainage, makes insoluble iron phosphates more available, helps make potash available, opens up stiff clay soils, has a binding effect on sandy soils, and goes a long wav towards ensuring fattening pastures and robust and fruitful crops.