asked the Taoiseach whether the Scientific Research Bureau has given consideration to the possibility of manufacturing superphosphate without the use of sulphuric acid; and whether, in view of the article by Mr. P.S. Syme in the New Zealand Journal of Agriculture, August 15th, 1942, on the manufacture, use and advantages of serpentine phosphate, any consideration has been given by the Bureau to the production here of this new type of fertiliser, having regard to the fact that we have the necessary raw material, namely, slippery rock or soap rock containing silicate of magnesia for admixture.
Ceisteanna—Questions. Oral Answers. - Manufacture of Superphosphate.
Superphosphate is a water-soluble phosphatic fertiliser which is normally manufactured by the treatment of phosphate rock with sulphuric acid. A concentrated superphosphate is made in the United States by the use of phosphoric acid in place of sulphuric acid, and the Bureau has under examination the question of such a process being operated here. Concentrated superphosphate possesses a much higher soluble phosphate content than ordinary superphosphate.
I should, perhaps, explain that in phosphatic fertilisers the phosphate may be soluble in water or in an aqueous solution of citric acid. The phosphate present in many mineral phosphates has to be converted to one or other of the soluble forms before it can be readily assimilated by plants. Phosphates which are citric-soluble are found to respond to the action of certain natural acids present in the soil. Both types have been found satisfactory in this country, but the water-soluble class have been preferred particularly for tillage crops.
Serpentine superphosphate is a fertiliser containing phosphate in the citric-soluble form. Other examples of such fertilisers are basic slag, certain forms of ground mineral phosphate and mineral phosphates which have been subjected to certain special treatments. Citric-soluble phosphates are held by some people to have an advantage over the water-soluble type in soils where there is a tendency for the phosphate to be "fixed," that is, rendered unavailable to plants when applied in the soluble form.
Serpentine superphosphate is the product obtained by mixing one part of ground serpentine with three parts of freshly-made superphosphate. Serpentine is a mineral composed mainly of magnesia and silica. The Bureau has not examined the possibility of the manufacture here of this type of fertiliser, and has no evidence that the use of such a material in this country would have any advantage over ordinary superphosphate. The investigations carried out by the Bureau have, however, included laboratory experiments on the treatment of Clare phosphate with magnesia and silica. Serpentine superphosphate is a reverted superphosphate, that is, one in which most of the water-soluble phosphate has been converted to the citric-soluble form. As already explained, this reduced solubility is regarded as an advantage with certain soils. It contains the magnesium and silica of the original serpentine, and its beneficial action has also been attributed in part to the presence of these and of traces of other elements such as cobalt, which is considered valuable on particular soils in New Zealand. Inasmuch as serpentine contains no phosphate, the phosphate content of serpentine superphosphate is reduced as compared with superphosphate according to the amount of serpentine added, and to this extent it must be considered largely as a diluent rather than an addition by way of a manurial ingredient.
The use of serpentine superphosphate was developed mainly in the U.S.S.R. and New Zealand. The primary object in using this particular fertiliser is not clear from the literature. It is said to be in a better mechanical condition than superphosphate but, as phosphates have been in short supply in New Zealand, part of the object may have been to ensure better distribution of the available supplies.
The Bureau's investigations in regard to phosphatic fertilisers have been mainly directed towards converting the insoluble phosphate present in Clare phosphate to the citric-soluble form. In this work, attention has been concentrated on the processes which appeared the most suitable to our conditions from the information available in regard to developments in other countries. The investigations have included experiments on a semi-technical scale on the heating of the rock alone, or with sodium carbonate, or lime. These experiments have shown that a product with a high degree of citric solubility can be obtained by treating ground Clare phosphate rock with sodium carbonate at a sufficiently high temperature. Consideration has also been given to investigating the merits of this process on a commercial scale, but as this would involve the allocation to experimental work of a large proportion of the very limited supplies of Clare phosphate available, it was decided that this part of the investigation should be postponed until the supply position improved, or until the fertilising value of the experimental material was confirmed by field trials.
The whole matter of the most suitable type of phosphatic fertiliser for use here in present circumstances is being actively pursued.
The Taoiseach stated that it appeared to the Scientific Research Bureau that the primary object in using this fertiliser was not clearly set out in the literature. Surely the Taoiseach and the members of the Research Bureau have studied the literature. It is clearly set out that the object is to prevent the fixation of soils with a high content of iron and aluminium. That occurs in many cases of acid soil. It would have the effect of stretching out the phosphate that is added in the way of artificial manure and that is, to a large extent, not recoverable by the plant where fixation occurs. Fixation does not occur in citric form and the purpose is to convert the phosphate from water-soluble to citric-soluble form. That is the whole purpose in adding silicate of magnesia. Our peculiar problem is that we are suffering from an acute shortage of the raw material of superphosphate. Will the Taoiseach have the matter further examined and have field experiments carried out as to the advantages of this superphosphate? Even in the present issue of the Scottish Journal of Agriculture, there is a very long article on this whole question of the manufacture of superphosphate and its advantages. Will the Taoiseach see that we are alive to this problem and that scientific discoveries of this nature will be made available to our farmers at the earliest opportunity?
As I have told the Deputy, this whole question of fertilisers is being actively pursued. As regards literature, I myself took pains to get the particular article referred to by the Deputy as I thought I would get something about manufacture in it. In the whole article there is only a passing reference to pastures, and there is nothing in it about manufacture.
Since I put down the question I have read an article in the present issue of the Scottish Journal of Agriculture.
The Deputy referred me to the New Zealand Journal of Agriculture of August 15th, 1942, and to an article there by a man named Syme. I have read that article, and there is nothing in it about the manufacture of this particular fertiliser.
The use of it.
The Deputy in his question put down the use and manufacture of it. There is only a passing reference to the use of it. The rest of the article is not informative at all.
I would refer the Taoiseach to another article in the Scottish journal.
I will look it up. I want to assure the Deputy that this whole question of fertilisers is being actively pursued by the Bureau and by the Department of Agriculture.
They are not pursuing it in the right direction.
Then the Deputy should be head of the whole lot to correct the Research Bureau and the rest.
We have not got such a thing, so far as agriculture is concerned.