Sept. 1, 1899.] THE TROPICAL AGRICULTURIST. 
175 
analyses to be strictly comparable, the legitimate 
conclusion is that the minimum amount of phos- 
phoric acitl in the fertile soils viz. -044 per cent is 
still so much above what is required ior the inirae- 
didte future, at least, that it is just as capable 
as a liigher proportion of meeting the wants of 
the cacao-trees ; and, certainly, if we go into the 
calculation of the ratio of supply to demand in the 
case of the minimum amount of potash and the 
minimum amount of phosphoric acid, we ficd that 
the ratio of the supply of phosphoric acid to the 
demand is much the greater. For the calculation 
to prove this we may assume that 01 per cent 
of a soil-ingredient to a depth of three feet weighs 
four tons per acre- The minimum amounts of 
phosphoric acid and of potash to a depth of three 
feet, in the fertile soils analysed will thus weigh 
respectively .3,942 lb. and 10,572 lb. per acre. In 
my analyses of the parts of the cacao tree, I esti- 
mated that, between the ages of 4^ and yeais, 
a year's demand* of an acre of cacao trees was 
for phospheric acid 13-41 lb., and for potash 78-32 
lb. Dividing the supply in each case by a year's 
demand, we get the ratio in the case of phosphoric- 
acid as 294 times, and in the case of potash only 
135 times that of the year's demand. 
However, the minimum amount of phosphoric 
acid was not associated in the same soil with the 
niiuinium, but with '169 percent of potash. 
If the same form of calculation as before is made 
with this percentage of potash, we hnd the ratio of 
supply to demand to be 193, still much below that 
of the phosphoric acid. Again, if the calculation he 
made based on the average, or maximum of either 
the total or readily available amounts of phosphoric 
acid and potash in the two sets of analyses the ad- 
vantage in favour of supply of phosperic acid is ac- 
centuated. It would thus appear that there is a 
greater likelihood of potash than of phosphoric acid 
being deficient in cacao soils. 
The following is the analysis of the sample of 
Venezuelan good soil referred to in the Govern- 
ment Analyst's report : — 
COMPOSITION OF AIE-DRIED SAMPLE OF VENEZUELA 
GOOD SOIL. 
Water .. .. .. 10-74 
Dry soil ... ... 89 26 
iOO-00 
COMPOSITION OF THE DEY BOIL. 
a Loss on ignition .. ... 7-610 
Iron oxide and Alumina . . 6-200 
Limy . . , -594 
Magnesia .. .. -782 
Potash .. .. -392 
Soda .. .. -177 
Phosphoric acid . . ... "147 
Sulphuric acid ... .. -036 
Chlorine .. -016 
lasoluble silicates ... .. 84-046 
100 000 
a Containine; nitrogen . . • . -071 
,, Carbon equal to humus . . -250 
,, Nitrogen as nitrates ... -00636 
* By a year's demand or requirement is meant the 
plant food appropriated by the annual increment to 
the trees and by a crop of fruit, i.e., seeds and pod- 
husks. If the pod-huaks were left out of the calcu- 
lation, as returnable to the soil, the ratio in favour 
of the phosphoric ;acid supply as compared with that 
of tthe potash would still be much the greater, viz., 
»n the proportion of 337 to 178. 
READILY AVAILABLE POTASH AND PHOSPHATES. 
Potash -1707 
Phosphoric acid ... . . -0820 
Why Professor Carmody refers to the propor- 
tion of phosphoric acid in this sample of soil as 
small is not obvious, as the amount is higher than 
in any of the eisrht fertile soils, save one. It is, 
however, slightly below the average of the 14 
average soils, with which he is dealing. 
As a set-off against the low percentage of total 
nitrogen, it has the highest propoi tion of any of 
the fifteen, of nitrogen in the form of nitric acid, 
thus suggesting that the soil is possessed of good 
nitrifying power ; but the amount of nitric acid 
found in a soil is not always an index to the 
nitrifying power. Nitrates being very soluble 
substances, the rain carries them down in the soil 
so that the same soil sampled in different states 
of the weather would yield differing results on 
analysis in respect of nitiates. 
Warrington and otiiers now employ a process for 
determining the nitrifying power of soils which is 
partly bacteriological and partly chemical. It 
consists essentially in seeding a convenient cul- 
ture-solution with a few grains of soil and 
noting by chemical tests at intervals of five days 
the vigour with which the nitrifying process pro- 
ceeds after it is started. If the culture solution 
is not affected, this is taken as evidence that there 
are no nitrifying organisms in the soil. 
In most of the West Indian samples of cacao 
soil, the moisture in the air-dried earth is higher 
in proportion to the organic matter and alumina 
present than in our Ceylon soils. Take, for 
example, the sample of good soil from Venezuela. 
Its chemical composition is such as we would 
associate with about 3 per cent of moisture, 
whereas it contains 10-74 per cent. The large 
amount of moisture must therefore be mainly due 
to the physical condition of the soil. 
The high percentage of chlorine referred to in 
the report on this sample of soil cannot, in view 
of the very small proportions found in the eight 
fertile soils, be regarded as an important indica- 
tion so far as fertility is concerned ; but it is of 
importance as affording a sanction for the use of 
chloride, that is muriate, of potash as a manure 
which is a cheaper salt of potash than the sulphate. 
I trust Professor Carmody will continue his 
interesting series of analyses of cacao soils, giving 
us some results obtained by the analysis of soils 
in which cacao has failed to grow or to yield 
satisfactory results. 
The following is the portion of Mr, Cochran's 
report and analyses referring to Ceylon soils :— 
Amongst samples of Ceylon ■ soils recently sent 
to me for analyses, two were Cacao Soils, lb 
may be interesting in the present connection 
to quote the analyses of these : No. 1 is the 
analysis of soil from a Forastero cacao field. 
No 2 is the analysis of soil from a Caracas 
cacao field. 
The sender of these soils has been good 
enough to furnish the following description of 
the fields. " The field where No. 1 sample was 
taken from has never yielded much cocoa per 
acre for some reason. The land is steep, and a 
fair amount ot rock in it. The soil is free 
and deep." 
" The soil in the fields from where the second 
sample came looks much better than No, 1 
sample; but the fields have been much longer, 
in cultivation. There are lots of small patches 
throughout the fields where the cacao has died 
