Dec. 2, 1901.] THE TROPICAL 
AGRICULTURIST. 
379 
bamboo, and if the section is made at C). that 
pith dries up acid the bud below is u,t times en- 
dangered. The section should be made either at 
C or at 02 as showa on the fig., and ue?er at CL. 
The bads B. are those left on the spur. D is an 
axillary bud which often fails to shoot. E ia a piece 
of the previous season's wood. 
When Best to Pkunb. 
For the winter pruning of deciduous trees. May, 
June, July and August are the best months. Pruning 
may be started directiy the wood is ripe, when the 
leavea fade and begin to drop off. It is reoomeDded 
to give to apricots and cherries a preiiniindry prun- 
ing in the late summer, after the crop has been 
gathered. Trees thus pruned are less subject to 
gumming and dying back, and the leaf buds have 
thus more time to transform into fruit buds, and 
to perfect themselves. 
As a rule older trees are ready for pruning before 
younger ones. 
In frosty localities, where stagnant cold air hangs 
about hollows and gullies, it is advisable to delay 
the pruning of vines, peaches, and plants whose sap 
moves early, until later in the season. This delays 
the period of active growth, and may save the 
crop. As regards the grape vine, late pruning is, if 
anything, also preferable to early pruning, in res- 
pect to yield of the crop and earliue?s of the period 
of maturity ; but of course where wide areas have 
to be gone through, it is not possible to delay uotil 
the right moment this operation. — Journal of the De- 
partment of Agriculture of Western Australia. 
, 
SOME RECENT INVESTIGATIONS IN 
THE CHEMISTRY OF AGRICULTURE. 
A Lecture delivered on College Day at the 
Saidapet College of Agriculture, Madras, by Dr' 
J. W. Leather, Ph. D„ F.I.C., &o.. Lecturer at 
the Imperial Forest School, Dehra Dun, N.-W.P 
When you did me the honour to ask me to read 
a paper on College Day, I thought that I could 
not well choose a more suitable subject than the 
one which has been aunouncid, namely, a brief ac- 
count of some of the recent work on the chemistry 
of agriculture. 
As a matter of fact, however, I have found it 
impossible, without unduly occupying your time, to 
deal with more than one or two subjects, and I have 
had to leave uunoticed the greater part of the very 
extensive work which has been done on vegetable 
physiology. 
Soils. 
There is perhaps no subject which has claimed 
the attention of the agricultural chemist more than 
the soil, and there is certainly no subject which is 
more deserving; at the same time it is one of the 
domains of agriculture ahout which, if we have 
learnt much in the past, we have much to leara in 
the future. 
Playfair when editing Laibig's Agricultural Chemis- 
try, expressed surprise that the chemist of that day 
should be content with the determinations of the 
amount of silicates and iron and alumina, leaving 
the potash, phosphoric acid, &c., undetermined. It 
■was a compariitivsly simple matter for the chemist 
to free himself from this criticism, and he proceeded 
to determine the amount of the valuable plant foods, 
the lime, potash, phosphoric acid and nitrogen, with 
very great precision. This told us how much of 
these ingredients were in the soil. 
As years passed on, it became evident that, valu 
able as this information was, it was insuliicient." 
The chemist would find what appeared to be only 
a small proportion of potash or phosphoric acid, 
whilst if a manure were given to supply the deficiency, 
it might happen that the crop did not I'espond to 
the more lib eral treatment in such a measure as 
one might have expected. Or, conversely, it was 
found that whilst a few tons of farm manure, or 
a few hundred pounds of more concentrated arti- 
ficial manures, would have a remarkable efftct on 
a crop, the actual amount of plant food contained 
in such manures, was far less than the soil itself 
contained. 
One explanation of this was provided by the teach- 
ings of the field exp'jriments at Rothamsted, which 
showed cleanly enough that all crops have not the 
same requirements. It was found, for instance, that 
the cereal crops were particularly effected fay a 
nitrogenous manure though at the same time it 
paid to give them mineral plant food also. Turnips 
and .Mangdls showed that if the supply of phosphoric 
acid were not liberal, they felt it keenly, and re- 
turned, for an application of comparatively small 
allowances of super-phosphates, a largely increased 
crop. * 
The third class of plants which fills an important 
place in English agriculture, namely, the Papilli- 
onacffl, behaved again differently, and often refused 
to glow at all in a field, however liberal the supply 
of manure might be. The latter is for several reasons 
perhaps not quite so suitable an example as the 
t .vo former, but the evidence, as you will see, went 
to show that the methods employed by the chemist 
in the analysis of soils, were by no means perfect. 
One fact that appeared very striking was that 
soils, which either appeared pjor from the chemical 
analysis, or were actually known to be poor agricul- 
turally, contained admittedly very much more plant 
food tho.n several, or indeed many, crops required. 
It was known that at the most, a good crop only 
required a few pounds, 10, 20 or 30, of potaah or 
phosphoric acid, whilst on the other hand soils rarely 
contained less than 1 per cent, of either of these 
piunt foods, usually indeed more than this, and such 
a proportion amounts to no less than about 4,000 lb. 
per acre in the surface soil, to say nothing of the 
stores which the sub soils were known to contain. 
It was clear that all this plant food could not 
be equally within the reach of the crops, that some 
portion of it must be in a different state of com- 
bination to another, the plant being able to assimilate 
the one more readily than the other. One commenced 
to speak therefore of " readily available plant food " 
as distinct from that wbich was not to. 
^yhilst a recognition of such a difference was easy, 
and the problem to be solved made clear, the method 
of differentiating between, say the portion of the 
phosphoric acid which the plant could readily ut. 
ilise, and that other portion of the same material 
which it could not, was by no means clear. 
ViUe offered a method, which was at least roseate 
on the surface. He said, why not divide the land 
to be examined into plots, and to one plot give all 
the valuable plant foods exceptiag one say phos- 
phoric acid, to another plot give all the several plant 
foods excepting another, say potash, and by provid» 
ing a series of manures each deficient in one particular 
food, surely, will not such a method enable one to 
tell, from the weight of crop raised, what the soil 
is deficient in ? 
The Rothamsted experimenter, had however shown 
very clearly that one cannot accept the answer which 
one sort of crop might give, as being that which 
woull be given by another sort of crop. And further- 
more, thai; in the case of field experiments with cropa 
one season is not sufficient to provide a definite answer, 
that, indeed the experiment must be repeated at least a 
numoer of times before one can eliminate from it 
the influences of season, and the original inequalities 
of the land. Such a method then becomes imprac- 
ticable, for the farmer does not wish to wait y-ars 
before he knows what sort of manure to apply to 
his crops. 
Latterly, Wilfart has experimented upon the valua 
of another method, based on somewhat similar lines. 
He raised the question whether, supposing a crop 
say of wheat, be grown in a soil which is deficient 
