LIME ADVOCATED.

Marlborough Express, Volume LXXVI, Issue 245, 17 October 1942, Page 2

LIME ADVOCATED.

REVERTING OF SUPER. SERPENTINE'S DRAWBACKS. The converslon of all superphosphate to lime-basic super was strongly advocated by Mr G. A. Law -

rence, an agricultural chemist, of Wellington, in contesting claims recently made by the Director-General of Agriculture, Mr A. H. Cockayne, for the serpentine -super mixture. Mr Coekayne's claim that three years' trials had proved that 1001b of serpentine --super would do the work of 1001b of straight super was ; an important admission, said Mr Lawrence, when it.was remembered for many years the Agriculture Department had advocated the use of straight super, and when this was added to the fact that serpentinesuper was, after all, only a form of basic super, BASIC MANURE SUPERIOR. Agricultural investigation the world over left no room to doubt that plant life responded more readily when reverted all-basic phosphates were applied. Experiments carried out with serpentine-super merely substantiated that rule. In other words, fixation of phosphate in the soil was largely uncontrolled when straight super was applied. "From recent articles in the Jour - nal of Agriculture, one would think that the use of phosphates other than in the form of super was a new departure," said Mr Lawrence. "The department is very late in waking up to this development when it is considered that basic, or reverted, phosphate has been manufactured in this country for the past 30 years." Some authorities had always condemned the unlimited application of straight super, owing to the heavy call it made on soil bases and the attendant risk of faulty fixation in the soil. ONE POINT AT ISSUE. Now that the department had ad - mittecl that the basic type of fertiliser was the best, the only point at issue was the best method of rendering superphosphate basic, by serpentine or by carbonate of lirne, Mr Lawrence continued. Lime-basic super had proved itself over a long period

of years, whereas serpentine-super had been tried only over the last year or two. The magnesia content of serpentine might be useful, but there were far more soils requiring added lime than added magnesia, and magnesia ■•containing limes were available. "Serpentine deposits are few and not always in suitable locations if long transport is to be avoided," said Mr Lawrence. "On the other hand, we have lime deposits being worked in numerous parts of the country where equipment and railway facilities are in constant use." There would therefore be considerable saving to the country if limestone instead of serpentine were used to revert superphosphate, he concluded, or, if the farmer were al» lowed to mix super and agricultural lime in the same proportions as serpentine and super were mixed, the saving to the farmer would be about £1 a ton.