150 tTHE TROPICAL AaRIUUL1'iJKl»'T. tSEI>T. 2, 1901. 
iield by Mr. Jamieson, of Aberdeen, as regards the 
harm done to the soil by the use o£ superphosphate. 
On his farm at Woburn he (the speaker) had a plot 
of land which had been manured yearly with super- 
phosphate for the iast 24 .years to his own knowledge. 
The soil had, at thp commencement, a very small 
amount of lime. 0-25 per cent, of carbonate of lime 
onlv, but the plot had not yet suffered from de- 
fioiencv of lime. There were other plots in the same 
field which had, indeed, so suffered, the lime having 
been removeii to a very great extent by the continued 
use of soluble nitrogenous manures. He could not, 
therefore, altogether agree with Mr. Hughes as to 
the great necessity for a manure which had the 
acid character taken away by admixture with ench 
a substance as finely ground lime. He had certainly 
come across soils which were so poor in lime as to 
require nothing so muoh as a good dressing of lime; he 
had not yet had experience with the new material 
which Mr. Hughes had just introduced, and so did 
not know whether that purpose might be well served 
by it ; but, if so, he ventured to suggest that it could 
be done without the necessity of buying a patent 
' manufactured manure. He was not going to discuss 
the question of citric acid, and how far it was a 
test of the availability of phosphatio materials ; 
but, as they had just heard the use of hot water 
mentioned for determining the amount of phospate 
available, and had been reminded that it did not 
occur in the soil, he might equally well point out 
that they did not have citric acid in the soil either. 
With regard to basic slag he did not think they 
had yet arrived at a solution of the cause of its 
utility. Attempts had been made to estimate this 
by the solubility in citric acid solution ; but there 
were many other things in the soil which might 
exercise an influence on the solubility of the 
materials applied to it. He would like to have seen 
Bome comparison given between basic slag and basic 
superphosphate with regard to their respective 
solubilities in citric acid solutions of different 
strength. What was the behaviour of each in a 
solution of the strength likely to be met with in 
soils? It might be taken for granted that there 
were soils which were s&rely in need of lime, and 
where fuperphospha'e might do harm ; but he would 
ask Mr. Hughes where was the advantage of using 
snperphopphate mixed with lime as compared with 
the use of a material like precipitated phosphate, 
which was just as Eoirble in c'tric acid as was Mr. 
Hughes' mixture. And then, even if it were granted 
that the mixture had advantages, what was there 
to prevent the faimer from buying the lime and 
the superphosphate separately and mixing them 
together himself 'i If Mr- Hughes said that a farmer 
could not do this, but would be bound to buy a 
patent manure, ready mixed, he fthe speaker) had 
still to learu that such a patent was of any value 
when it was taken out. If the farmer thought it 
a good thing to neutralise superphosphate by lime 
he v/ould mix the two materials together, patent or 
no patent. There was, to his mind, a further 
disadvantage, inasmuch as Mr. Hughes did not suffi- 
ciently imitate the action of the soil in the mixing 
together of the two materials. If superphosphate 
was taken and ground lime added to it, the lime 
did not work through the whole mass, but there 
was only a supeifioial action, the external portion 
being neutralised and the inner left as it was. So 
one did not get a through neutralisation and dis- 
tribution of precipitated phosphate purely by a 
mechaniral mixing of the ground lime and super- 
phosphate. The only advantage apparent to him 
was that there might bo some places abroad or in 
the colonies where lime was not obtainable, or 
where it wts so expensive that its use in any 
quantity was practically out of the question. _ If 
goil-t in such places were very deficient in lime 
one might certainly get some advantnge by using 
lime and superphosphate together, but, for that 
piatter, ho did not see the advantage which the new 
material hid over precipitated phosphate in this 
respect, nor why one should not get the materials 
separately and mix them for himself. 
Mr. F. J. Lloyd said that it was now about a 
quarter of a century since any new manure wa.s 
brought before the agricultural world and that was 
a sufficient reason for thanking Mr. Hughes for 
having brought before them a new manure. Whether 
it would prove of value or not, time only could 
show. The author had given two reasons why it 
might prove valuable : first, because from the em- 
pirical tests made there was every reason to suppose 
that the phosphate of lime would be quite as 
available to the plant as the phosphate in super- 
phosphate, and more available than that in basic 
slag, which for ihe last twenty years had proved 
a valuable and effective manure ; and, secondly, 
because it was not acid, and therefore suitable for 
soils of an acid character or deficient in lime. 
There was another reason, in his own opinion, why 
Mr. Hughes's mixture should be a valuable manure. 
The progress of science in agriculture had of late 
years been mainly bacteriological. As lecturer on 
agriculture at Kipj|^ College, it was his duty to 
explain why we manure the land. Formerly there 
were only two reasons : one, to supply a deficiency 
of any material in the soil ; and the other to supply 
material of a nutritive character to the particular 
crop to be grown. But science had recantly shown a 
third reason of considerable importance, and one 
which threw light on the action of manures hitherto 
difficult to explain. The soil was full of bacteria, 
and many of the plants grown in the soil were 
affected by bacteria. These bacteria must be fed 
in order to carry on the functions of their life. 
Taking the bacteria most studied, those which pro- 
duced nitrification in the soil, it had been proved 
that they were most active in a material of an 
alkaline nature, and did not act and grow, except 
slowly, in any material of an acid nature ; therefore, 
if one added something to the soil which, while it 
supplied the plant with one variety of food, also 
supplied conditions which enable the bacteria to 
supply another form of f' od, and helped the nitrify- 
ing organisms to carry on their woik, that manure 
served a doubla purpose. Basic slag had had that 
effect, because of the double ao: ion brought into 
play — the supply of nitrogenous matter to t' e plant 
as well as phosphatic food. Arguing a priori, there 
was every reason to suppose that this basic super- 
phosphate would have the same effect, and he 
really believed that they had to thank Mr. Hughes 
for the introdution of a material of considerable 
value. It was all very well to say that, if the soil 
contained lime and acid, superphosphate did no 
injury; but they had to deal with the British 
farmer, and he was a peculiar man. For the last 
twenty years liming had gone out of fashion, and 
the soil was deprived of lime as much by the use 
of nitrogenous manures as by superphosphate. Con- 
sequently, the soils of the country were becoming 
more and more deficient in lime, and an acid su- 
perphosphate, was not, in his opinion, likely to 
have the same effect as a basic superphopphate, 
which gave the farmer the lime and available phos- 
phates at the same time. He would not enter into 
the question of the estimation of the value of this 
material; but he did hope, as an official agricul- 
tural analyst having to carry out the Fertilisers 
Act, that those who put the manure on the market 
would give a distinct guarantee as to what it should 
contain. He was sure they would find it; beneficial 
to themselves, and it would be a subject for future 
discussion to determine whether that guarantee was 
a satisfactory one or not. He felt personally grate- 
ful to Mr. Hughes for bringing this valuable com- 
munication fotwavd. 
Mr. J. EuFFLE agreed with the last speaker. He 
was not surprised that Dr. Voelcker should throw 
cold water on this new idea, for it was just what 
happened on the introduction of basic sjag 20 year 
