Jan. 1, 1902.] 
,THE TROPICAL AGRICULTURIST. 
469 
ters of the work under noUce deal ^ifli^ 
Assam soils, (3) Manures available, W Notes 
on the tea soil of each Assam District^ 
These are mainly special to the .f ^at Indian 
tea region. But the second, which takes up 
''Ohem ica Characteristics," contains much 
that is of universal interest.. This we hav| 
carefully extracted and quote in our daily and 
T ^ The point, we notice, most emphasized is 
tliat it is not alone tvhat chemicals a soil 
contains, but hoiv they occiiv there that 
determines their eflect on 'V'd usefulness for 
tPM • sandv soil contains chemicals in tlie 
free statefbut in clay, combined and there- 
forlnot so readily nourishing; the tea bush 
We commend the additions Mr. Mann has 
made to the study of tea soils to the attention 
of all interested. 
CHEMICAL COMPOSITION OF TEA 
SOILS. 
fFroni " The Tea Soils of Assam'' by Mr. H. 
' H. Mann, B. Sc.) 
Both Mr. Bamber'8 and my own resnlta are how- 
ever almost entirely derived from analysis of soils 
obtlined from various tea gardens of Ceylon and 
Assam! and it remains to consider how far such ana 
Wses can be of value in the decision of such pomts 
as the suitability of land for planting, or the manuring 
reaaisite for such land. In conBidenng Assam soils 
on\ L met at the outset by a difficulty judged by 
all standards of English agriculture. Many of the 
best tea-soils, as shown by the percentage figures, 
seem much poorer than would be expected of virgin 
and good tea yielding land, and poorer even than 
o her soil which is really much inferior for tea 
production. It would seem, at first sight, that analysis 
is of no value here, and that the poorer soils chemi- 
oftllv are the better ones actually and agriculturally 
But it these analyses be considered in another way 
the apparent contradiction disappears. There is in 
every soil a very large amount of sand which acts 
as a support to the plant, but in every other respect 
merely as a diluent of the valuable soil constituents. 
It would, therefore, seem that in order to ascertain 
the real actual richness of the soil for plant pro- 
duction, one's figures should be calculated not on 
the soil as a whole, but on that part which is no 
sand What previously seemed to be the worst soil 
bv far, now proves richer in every important ingre- 
dient (save the Potash). This is so universal m Assam 
soils that one may lay down as a general rule thac 
the power of land to produce luxuriant tea must in 
the future be determined not by the percentage ol 
valuable matter In the soil as a whole, but rathe"" 
the soil less the sand, which latter acts in la"^?® 
measure as a diluent of the other materials. But 
this argument we have lost sight of one iraporta^'' 
matter. While the amount expressed in percentages 
of the soil as a whole may not represent the pow" 
of giving luxuriance to the plants, it uudoubted'y 
Bhowa the extent of the soil resources, i.e., th^ 
ultimate amount of plant food contained in th® 
soil. Such a conclusion would be justified i*^ 
the' soils were of the same depth, and if the roots 
penetrated as easily in one as in the other. And in 
practice the conclusion is shown to be just by the 
rapid exhaustion of sands overlying clay, which at 
first give exceedingly luxuriant and fine tea, but 
which become exhausted more rapidly than any other 
type of land in Assam. Though, calculated in the 
non-sandy part of the soil, they were very rich to 
Btart with, yet the total amount of plant food was 
Bmall and was rapidly exhausted, while the roots 
were 'unable to seek fresh supplies further afield 
because of the underlying clay. In the example I have 
jjaJseo, UoweTor, it is otberwiae, The soil No. I has at 
least twenty feet depth of soil in which to range 
without meeting clay or water, and hence produces 
luxuriant tea at the beginning, and in addition lasts 
an almost indefinite time. 
We have therefore to considfr in a soil analysis : — 
1. The concentration of the soil constituents, i.e., 
the amount of the valuable matters in the part of the 
soil other than sand. This determines the luxuriance 
of the plants and probably the value of the tea. 
2. The absolute amount of the ingredients of value 
as represented by the percentages in the soil as a 
whole. This determines the permanence of the 
plant without manuring, but only if taken in con- 
junction with. 
3. The available depth of the soil, which may 
counterbalance the apparent absolute poverty (No. 2) 
of the land if this depth is sufficiently great. 
METHODS OF TAKING SAMPLES OP SOIL 
FOR ANALYSIS. 
In sending a soil for analysis, therefore, in order 
to satisfy consideration No. 3, the character of the 
subsoil should always be stated, and in addition the 
depth of the subsoil water, as these may have a para- 
mount influence in determining the meaning of the 
analysis. The actual sample sent should always be 
taken in the following manner. Dig a hole in the plot 
of which an analysis is desired, fifteen inches deep, 
leaving a block in the centre of the hole 6 inches 
square. This block is therefore 6" by 6" by 15" in 
size. Have a box made of these inside measurements 
and invert it over the block of soil, and then remove 
the whole, — box, soil, and all, — by putting a spade 
underneath the block. Then fasten a cover on the 
box and send to the analyst, marking the end of the 
box which contains what was originally the surface 
soil. The analyst has thus a block showing the 
layers of soil as they occurred in situ down to 15 
inches deep, and valuable results may often be drawn 
from mere observation of them, which would be en- 
tirely missed if merely a shovelful of soil down to the 
same depth were sent for examinatiou. 
IMPORTANCE OF VARIOUS SOIL UONSTL 
TUENTS. 
Although the constituents always present in soil are 
many in number, yet those which have any interest 
from an agricultural point of view are comparatively 
few. Some seem to have no necessary functions in 
regard to plant life. Such are the silica, the alumina 
an'd the soda. Others are, one may eay, always pre- 
sent in far greater amount than the plant requires. 
Such are the oxide of iron, the magnesia, and the 
Sulphuric acid, but with these constituents it may be 
that they have to be present in some particular form 
to be useful to the plant, and thus they may be an 
essential element in the fertility of a soil. And third 
there are those ingredients required by every plant, 
and upon whose absolute and relative quantity de- 
pends primarily the fertility of the land. Such are 
the organic matter, the lime, the phosphoric acid, the 
potash, and the nitrogen. 
ORGANIC MATTER AND NITROGEN. 
These two constituents of the soil are intimately 
connected. In fact the total useful nitrogen in the 
soil is or has been contained in the organic matter. 
I say "has been" because at the time the tea plant 
utilises it, it usually has been converted into nitrates 
by the microbes of the soil. For many years it has 
been supposed that this conversion into nitrates 
always took place before absorption of nitrogen by 
the plant, and it is only recent investigations 
which seem to have shown that the nitrogen in 
the organic matter itself without previous change 
may form the food of plants. The determina- 
tion of the nitrates actually present in soil 
generally, however, gives little information aa 
to the resources of the soil in food supply since the 
nitrogen in this form in so soluble a condition, that the 
first rain storm may wash the whole into the drains. 
The permanent supply of soil nitrogen is that con- 
tained in the " orgaaig waUef " or " humus," an(^ 
