FOOD FOR THE SOIL.

New Zealand Herald, Volume LXIX, Issue 21168, 28 April 1932, Page 14

FOOD FOR THE SOIL.

ADVANTAGES OF LIME. NECESSARY CONSIDERATIONS. BY KEHETI. In view of tiio relatively high price of ,], artifical fertilisers and the continued low j i price of primary produce many farmers |, have been turning their attention to lim- x ing us a partial substitute for top-dressing, j The wisdom, or otherwise of this procedure ~ depends entirely oil circumstances and on j the. response which attends liming. in some cases phosphatic manures give little ( response uidess preceeded by a dressing of lime, but such cases are the exception rather than the rule. So long as dressings of phosphate continue to give good ( returns it is doubtful if liming can ad- ( vantageously replace them, though it may ( with advantage be used to supplement phosphatic dressings. Lime deficiency may lie rectified by the . application of any fertiliser containing •• combined " lime (e.g. slag, superphos- . phate, gypsum, nitrolini, etc.) by liming, or by feeding licks to stock grazing the , affected areas. Slag contains about 41 p.c. of lime (CaO) but most of this is "combined with phosphoric acid, oulv about p. i■ being " free " lime, capable of neutralising soil acidity. Some ground rock phosphates , may contain up to 8 p.c. of " free. " lime, but. the "total" lime present may bo much higher; some manure firms stale that a line of phosphatic fertiliser contains nearly half a ton of lime to each j ton of manure. Lime In Combine Form. While this statement may be undeniably true, it is well to bear in mind that most I of the lime is present ill a combined form, the quantity of " free " lime present being equal to slightly over cwt, of ground limestone in each ton of the manure, i.e., about Is 6d worth. The "combined" lime is valuable in cases of calcium deficiency, but it is only the part classed as " free " lime which is of any value foi rectifying acidity. In ground limestone all thy lime is uncombined or " free " and available for neutralising acidity. Superphosphate is usually classed as an acid manure, but experiments conducted over a period of 78 years at Rothamstead, in England, with annual dressings of superphosphate on one plot, show* no increase in acidity o\ci uninanurcd plots, and these results are confirmed by similar experiments conducted in United States America. Sulphate of ammonia, however, definitely makes the soil more acid, and whenever possible its application should be preceded by a dressing of lime. The two must not be mixed together or loss of ammonia may result. The point is sometimes raised whether soft marly lime is as good as hard crystalline Muff* The question is almost entirely one of quality and the lime should be bought on analysis; some farmers are of the. opinion that soft marly lime gives a quicker response, as it dissolves more rapidlv under the action of rain, but this is a 'moot point. Soft limestones are usually of lower grade (75 85 p.c.) than hard crystalline limes (90-95 p.c.), but, being more easily ground may be much I cheaper or more finely ground. An Important Factor. Fineness of grinding is an important J factor in determining the rapidity of action of agricultural lime, but so far has received insuflicent attention. The more finely ground the lime the more quickly it will act. Soft marly lime is equally as valuable unit for unit, as hard crystalline limestone. For instance if you can get lime analysing 75 p.c. delivered on your farm for 16s a ton, you can afford to pay for 90 p.c. lime delivered 90-75 x 16 = 19s 2£d per ton. provided the fineness of grinding is equal iu both cases. Buy your lime on analysis. The following benefits arc usually supposed to attend heavy dressings of lime:— (1) Clay soil is made more friable: (2) lime assists very materially in retaining manures in the soil so that they are not washed out by rain; (3) corrects acidity ov sourness in soils (very heavy dressings may be necessary): (4) stimulates the growth of clovers; (5) increases the lime content of pasture grown on the limed area: (6) by the process of base exchange | sets free supplies of potash and phosphate j not, otherwise available for use by plants. | ft is unfortunate that after relating the i above list of good points orie has to ob- | serve that field plot experiments, carried j out in various parts of the country, rarely I show the expected increase in yield on ! plots treated with lime when compared i with untreated plots. However, other points beside pasture yield have to be ; considered in determining the value of a j manurial dressing; the health of the stock 1 grazing the dressed fields is of prime ini- , portancc; its effect, on sterility, abortion, and butter fa( production are all points in no way related to the yield, but of great moment to the farmer. Massey College Experiments. With a view to obtaining more definite information in these respects, a eoniprcHiensive experiment has been undertaken at Massey College. Half the paddocks on the dairy farm have been limed at the rate of one. ton to (he acre, but oilierwise receive similar manurial treatment to the remaining paddocks; the dairy herd has been divided into I wo, one half being grazed constantly on limed fields, while i the other herd is being grazed on uulimed fields. Subsequent dressings of bine : are to be at Ihe rate of scwt. per acre ; annually. i Records are being kept of incidence of : disease, etc. Further than this the milk from the two herds is at intervals being ! separately manufactured into cheese, to i see if there may be some relation between I liming, and quality of milk for cheese proI duction. In an experiment of this nature | it would be unwise to attempt premature | statement of results, and these will necesI sarilv be somewhat slow in coming to I hand as it. is desirable to have at least ! two season's figures on hand before exj pressing any opinion on so controversial a ! matter as " To lime or not, to lime.'