Aug. 1, 1903.] THE TKOPICAL 
AGRICULTURIST. 
83 
basic slag ofQ wouders where snpeiphofphfite had 
been fonnd a difdoult manuie to apply. But lliere 
still rernained a residuum of curious failures — certaia 
Foils which did not seem to respond iu the way one 
would expect to basic slag. It was not always 
possible at first sight to predict why those faiiurea 
occurred. Waiiy happened ou soils, almost acid in 
character, which 7,eie distinctly -waDtiMg in Sirae, and 
on soils where phosphates were deficient. Cert-iin 
classes of .?andy and giavelly soils required botli the 
liine and the pihosphato, and yet they gave very in- 
different returns when b.isic slag was placed upon 
them. That miglit be due to the physical couditious 
of the soil or waul of water ; but at the present time 
it must be accepted as an experimental fact that basic 
slag utterly failed to answer expectations on such 
soils. Mr. Hughes had put forward his particular 
manure as likely to be most efficacious in dealing 
with that class of soil. Mr. Hughes had raised the 
question of solubility in two senses. He had, per- 
haps, not distinguished enough between the solu- 
bility in water which chaiactei ised the superphosphates 
and the solubility in the weak acid test solution which 
characterised the new manure. If solubility in 
water had a virtue at all, it was .that it ensured in the 
soil the distribution of the manure. Superphosphate 
applied to the soil was washed down by the soil 
water dissolved in it, and promptly re-nrecipitated 
inside the soil wherever it met with a pardcle of car- 
bonate of lime, and was then re-precipitated in the 
same form as that in which the phosphate of lime 
must be present in Mr. Hughes's manure, i.e., the sup- 
erphosphate of a soil containing any carbonate of lime 
would eventually result in the precipitated phosphate 
under discussion, only the mere fact that it had been 
precipitated inside the soil from the solution formed 
on the surface ensured an intimate and local distribu- 
tion under the soil, which could not be obtained by 
any form of manure spreader followed up by cultiva- 
tion. That, he took it, was the great advantage 
which superphosphate possessed over any other form 
of phosphate ; and the fineness of grinding which had 
proved to be so effective in the case of some 
mineral phosphates and basic slag, was an 
attempt to reproduce that intimate distribu- 
tion in an artificial fashion. Mr. Hughes had 
placed before them as one of the chief tests of the 
merits of the manure as compared with the others 
the superior solubility the substance possessed iu a 
particular solution of citric acid. While he did not 
wish to depreciate the value of such a test as applied 
to any manure, it was necessary ?s far as possible 
that laboratory <-xperiments should be checked by 
experiments in the field, because the soil was au 
extraordinary complex body. It was very difficult to 
regard the soil as otherwise than simply so much 
inert material which would re act as it did in the 
laboratory. So far from that being the case the soil 
was only a store-house of living orgauisms ; and it 
must always be remembered that it was a medium for 
supplying the plant with water. There were curious 
differences in the surface which the soil particles 
possessed. The surface of a cubic foot of clay soil 
amounted to something like two or three acres, 
whereas in a sandy soil the surface was reduced down 
to less than one acre. There were all sorts of such 
curious differences on the border line between physios 
and chemistry in the absorption of soluble material, 
and in the way they would afterwards be yielded up 
either to the soil water or to the natural acid solvent 
which the sap of the plant possessed. He, therefore 
considered that they should proceed slowly in deduc- 
tions obtained from laboratory experiments compared 
with field practice; laboratory results must be checked 
by actual field tiials. He would have been pleased if 
Mr. Hughes had brought forward a more exact 
;>ccount of some of the field trials. Mr. Hughes laid 
down that basic slag would only act upon, compara- 
lively speaking, sour acid soils which had 
been deprived of their lims. He was rather iuclined 
to quo:>tiou that statement. Basic slag acted on a 
good many v.Uuable clay soils which could in no way 
be described rs acid soils; iu fact, it was a very 
difScnlt thing to say where the acid soil began. He 
thought it was necessary to push the examination 
of an acid soil a little further thau mert-ly deter- 
miaiug the amount pf lime it contained. The 
laboratory with which he was coanected I. ad been for 
some considerable time engaged in examining not 
merely the lime contaiued iu a number of soils, but 
the amouiit of that lime present in a basic condition 
i.e., the amount of the caibouate and ihe ail-.ali earth 
wiiioh they contained. It must be remembered that 
the lime which was present in a soil must be present 
as a sulphate ; it might be lime as silicate, bitt it 
might not be carbonate of iime, which was the base 
that any soil acted as a ueutraliser of the acids pro- 
duced by decay. He had found many fertile soils, 
showing CO signs of sourness, wliich contained no 
measurable quantity of carbonate of lime, seeming to 
be iu an absolutely ijeutral condition, having neither 
acid or alkali, and yet which carried very good crops. 
Where the bases which seemed to be necessary for so 
many of the vital processes came from in those soils he 
could not say at the present moment. He thought it 
was necessary to revise their classification and ideas 
of wha? constituted an acid soil, and to examine more 
closely with regard to the preseu«e or absence 
not only of calcium, but of thgse carbonates of 
calcium which constituted the active bases of the 
soil. Turning to the more practical question of the 
use of lime, he was inclined to difl'er from Mr. Hughes's 
remarks that the calcium carbonate itself, when it 
was once found in the soil, was of no service. It 
seemed to him that it was one of the most valuable 
things if it got freely into solution. One of the 
most characteristic substances found in drainage 
water was calcium bicarbouate. If any lime were 
applied to the soil and became calcium ca,rbouate, it 
was bound to circulate in the soil in the form of 
calcium bicarbonate. He wished to ask Mr. Hughes 
if he had considered whether, ou the whole, it was 
economical from the larger standpoint to first 
of all make a superphosphate and then to pro- 
ceed to neutralise that with lime, so to speak, to 
destroy the material which had already cost money, 
it had been his practice for some considerable time, 
in dealing with soils where basic slag did not seem to 
answer, and where, from the absence of lime, super- 
phosphate was not likely to do much good, to make 
up a mixture of superphosphate with some other 
ground phosphate, which was left for some little time 
to re-act, the mixture then being applied to the soli. He 
always obtained very good resu ts from such a mixture" 
The acid which might be on some occasions iujuiious 
in such soils had been removed iu the very advauta- 
geous way of passing over more calcium phosphate. 
He would like to ask Mr. Hu,hes whether the sub 
stance might not be improved by first of all neutralis- 
ing the superphosphate with a neutral phosphate, and 
then, if need be, adding the requisite amount of lime 
to produce the actual alkaline reaoticn. In advocating 
his manure Mr. Hughes was once more recalling to 
farmers the importance of the use of limo upon their 
soil, a most important consideration. Everywhere 
one heard that the lime kiln which used to be 
on the estate had now tumbled to pieces, and 
the farmers instead of putting lime ou the land 
used superphosphate and phosphate of lime, think- 
ing that absolved them from the necessity 
of treating the land with occasional dressings 
of caustic iime or even chalk, which used to be 
a staple part of the routine of agriculture. It was 
impossible to hammer too much into farmer the fact 
that superphosphate and phosphate of lime were not 
lime at all in the sense in which caustic lime originally 
was used, The use of an artificial mauure, so far 
from absolving the farmer from the necessity of 
