PHOSPHATE.

New Zealand Herald, Volume LXVIII, Issue 20880, 23 May 1931, Page 14

PHOSPHATE.

gir ; I have read with interest the article by "Vivian" in connection with blue iron earth in the Hunua-Drury district. 1 have examined a number of samples of similar earth and the blue colour is derived from hvdrated phosphate of iron, which is also known as vivianite. Phosphate of iron is a very useful fertiliser, and if it could be found in large quantity might be particularly useful on some of the pumice lands, which are deficient in iron. In the Auckland province there are certain tracts of land which will not support cattle satisfactorily, due largely to shortage of iron in the soil. The usual trouble with vivianite is that it is so diluted in the rock or earth that it does not pay to get it out and bag and transport it. I have come across blue earths of this type containing from 2 to about 10 per cent, of phosphate of iron, and it is very doubtful whether such earth would be valuable enough to cover the labour involved alone. There is another form of vivianite which occurs in nodules, and contains about 70 per cent, of phosphate of iron. In the handling of blue earth there should be no health reason to consider, but there is usually the very serious question that it does not pay anybody to handle such propositions. The expenses of handling, etc., are generally far greater than the value of the product, and presumably that is why the Government department is apparently not greatly interested. Possibly a few farmers in the locality could get out a few hundred tons at their own expense, which would enable them to try the fertiliser in a practical way and get some idea of the expense associated with the project. Alf. J. Parker, f.c.s.