ENRICHING THE SOIL

Otago Witness, Issue 3509, 14 June 1921, Page 9

ENRICHING THE SOIL

USE OF FERTILISERS. ANNUAL DEPARTMENTAL REVIEW. Statistics of artificial fertilisers imported into New Zealand during the year ended March. 31, 1921, are now available, and have been specially compiled for the New Zealand Journal of Agriculture. Reviewing these returns, there are several points of interest, which call for comment, and well merit, the attention (writes B. U. Aston, F.1.C., chemist to the department, in the May issue of the journal). In round figures the gross quantity of fertilisers imported shows the great increase of about 60.000 tons over the figures for the previous year, the actual figures being 142.357 tons, against 60.833 tons. J he fertilisers imported wore chiefly phosphates of various kinds, and although the other two classes of fertilisers, the potassic and the I nitrogenous, show large increases, I ho amount of these relative to the total is very small, being about 5a per cent, j Considering the nhosphatio fertilisers, it ! will be seen that basic slag is now coming lo hand in quantities which show that, in ; spite of the high prico, there is still a great demand for it. A notable feature

of these slag imports is the re-entry of Belgium, France, Luxemburg, and Holland into the New Zealand trade. From Belgium came 4590 lons, Franco 75 tons, Luxemburg 1000 tons, and Holland 300 tons. In fact, New Zealand received more slag from the Continent of Europe than from Great Britain (which sent about 5000 tons). It will be interesting to watch the result of the competition which will result between basic slag and other finely-divided insoluble phosphates, such as ground highgrade Pacific phosphate, when this is available in as finely-ground a state as slag. A superiority of phosphate rock over the slag lies in the tact that there need bo no anxiety as to its poisonous nature, whereas a recent research indicates that animals grazed on recently-slagged pastures may be poisoned by the particles which cling to the plants eaten. Until there has been sufficient rain to wash the slag from the grass, stock should not have access to recently-dressed land. When we consider that both slag arid ground phosphate reek have their phosphate in the state insoluble in water, but that whereas slag only eontains 16 per cent., Nauru phosphate contains sonic 40 per cent, of anhydrous phosphoric acid, it is difficult to believe that any superiority in the solubility cf slag phosphate in (he soil water cannot be counter-balanced by fine grinding of phosphate rock. 1 his opinion applies, of course, to just those conditions of soil and climate whii h would indicate success in the application of basic slag—namely, for top-dress-ing old pasture in districts (1) where tho soil is not too dry, in a most climate with a welldistributed rainfall; (2) where the soil requires a phosphate fertiliser; and (3! where leguminous plants, especially white clover, are present in the pastures. The next cause for congratulation one sees is the greatly-increased quantity of superphosphate received —41,060 tons, as against 16,000 tons in the previous year. Superphosphate certainly has its place in the present system of New Zealand agri-; culture, and when it cannot be obtained, production of winter feed in all districts drier than the average must; suffer. llow far superphosphate can bo replaced by finely-ground phosphate rock is, of course, a matter for experiment in the field. It is interesting to notice that those ports serving the drier districts of New Zealand receive superphosphate in much greater proportion than insoluble phosphate. Ihus Napier, supplying tho driest district in the North Island, imported 1200 tons of superphosphate, hut only 200 tans of insoluble phosphate; whereas New Plymouth, on the wetter west coast, received 2500 tons of superphosphate, as against 400 tons of insoluble phosphate. Lyttelton, supplving a district drier than the average in the South Island, took 6000 tons of superphosphate, compared with 3500 tons of insoluble phosphate; whereas Invercargill, supplying a very moist area, received only 4009 tons of superphosphate and 7000 tons of insoluble phosphate. The figures for Wellington, Auckland, and Dunedin may also bo given, although at the two latter places is manufactured a certain quantity of superphosphate, which would modify the conclusions to be drawn from the figures. The latter are as follow :—Wellington, 9500 tons superphosphate, 11,000 tons insoluble phosphate; Dunedin, 800 tons super, 13,000 tons insoluble; Auckland, 14,000 tons super, 42,000 tons insoluble. A point most worthy of notice Ls the very great increase in tho amount of rock phosphato imported over that for the previous year, the figures having 1 rounded from 39.000 tons to 70,000 tons. The writer is strongly of opinion that this is the best form in which to purchase phosphate, protided that it be used in a condition which will compare in fineness with basic slag; at least 80' per rent, of the phosphato should pass a 10,000-mesh sieve. The method advocated by the writer of economising phosphate by application of lime has been tested on a piece of land which had been heavily manured wilh phosphate in the past. It is a matter of common practice in the Waikato to manure heavilv with phosphato year after year. The writer suggested that the necessity for this was due to the fact that the phosphate of lime was being converted in tho soil into phosphate of iron and, aluminium, which, in the absence of lime, would !>o comparatively unavailable. It was sugg.sted that, by appropriate liming, the reversion of phosph ite to this form could Ire prevented, or that when it had taken place tho phosphate of iron or alumina could be reconverted to the calcium compound. In the experiment referred to (conducted by the manager of the Ruakura Farm of Instruction) the control plot only gave 1 ton lOcwt of hay pier acre, whereas the pilot limed with a ton of ground-burnt lime yielded 2 tons Eowt of bay, as compared with 2 tons 9cwt given by Ephos phosphate (3ewt), and 2 tons sewt by 1 ton of ground carbonate of lime. Such data as these make one seriously consider whether much of the phosphate applied to the northern lands is not being wasted by the absence of sufficient lime in the soil to ensure the maximum results.

FARMERS’ UN! ON CONFERENCE.

CHRISTCHURCH, June 10 At the Farmers’ Union Conference i lemit that the ‘ preference to unionists” clause i in awards has outlived its usefulness and | should be excluded from awards, was car- ; ried. With respect to a remit that the j Government be asked to continue control i of wheat for the 1922-23 season, an amendment was carried that the matter be re- ; ferred to all branches, and that the South . Canterbury and Otago executives 1 e le- j quested to act- similarly.

THE FRIGE OF WHEAT,

A Wellington Press Association telegram states that the Minister of Agriculture has notified in last week's Gazette that the Government has undertaken to purchase from vvbeatgrowers all good milling wheat of the 1921-22 season at the following minimum prices:—Tuscans, 5s 6d per bushel, I f.0.b.; Hunters, 5s 9d; pearl, 6s 3d. An increment of Jd per bushel per month will bo added to the above prices for wheat dealt with between May 1, 1822, and October 31, 1922. Market rates will be paid in excess of tho above guaranteed minimum prices. If necessary, to determine the market rates, the Government will be guided by the following principle: “In the event of any adjustment in prices being necessary, the Government will be guided by the world’s market value of wheat in February, 1922, of a similar quality to New Zealand wheat, having regard to the necessary adjustment between tho North Island and the South Island; but in any ease the purchase price will not be less than the minimum stated above for respective varieties, with the monthly increase.”