New Methods Of Making Phosphate Fertiliser In N.Z.

Bay of Plenty Beacon, Volume 15, Issue 28, 1 May 1950, Page 5

New Methods Of Making Phosphate Fertiliser In N.Z.

The conversion of Nauru rockphosphate into superphosphate, so Valued on Bay of Plenty farms, using sulphuric acid, necessitates the importation of vast quantities of Texas sulphur. This means the spending of dollars and dependence on supplies of sulphur, which are being rapidly exhausted. Hence the importance both of getting the most out of superphosphate, and of investigating methods other than the use of sulphuric acid for making rock-phosphate available to plants. One method of making full use of superphosphate is to “revert” it to a form less water-soluble but still equally available to plants. This has long been done by addition of lime, but a method of wholesale reversion, discovered at the Dominion Laboratory, Department of Scientific and Industrial Research, consists in adding to three parts of warm superphosphate one part by weight of serpentine rock, whereby magnesia instead of lime is added. Over 100,000 tons of serpentinesuperphosphate were made last •year. In the report of a U.N. Commission on Natural Resources it is claimed by officers of the N.Z. Department of Agriculture that 4cwt per acre of this compound is as effective as 4cwt of straight superphosphate. This could mean a saving of a quarter of the imports of rock-phosphate and of sulphur.