f 
Jan. 2, 1899.] Supplement In the " 
referred to by liim as non-existent in a country 
where rotation of crops is the rule, do occur in 
other cou?itries where rotation is either not 
practised though possible, or is impracticable, and 
in such cases nitragin would serve its end. But 
still the demand for it would be but a limited one. 
♦ 
THE ANALYSIS OF SOIL AS A GUIDE 
TO ITS FERTILITY'. 
[Dr. Dyer next confine? his attention to the 
estimations of pliOfpiioiic acid, but there is so 
much of technical detail in this part of the paper 
that we have summarized his remarks, touching 
upon the most important results obtained. He 
Tarnishes us with an elaborate table showing the 
determinations i)f both total and citric-acid-soluble 
pho.-phoric acid in the Rottamsoead plots referred 
to, and taking the previous treatment of -the land 
into considerations, he mukes certain important 
deductions. He shows that judging by the pro- 
duce in crop the citric-acid-soluble phosphoiic 
acid indicates the fertility of a soil as regards its 
phosphoric acid more correctly than total phos- 
phoric acid dues : and from a general consideration 
of the results of a long series of analyses he 
ventures to draw a provisional conclusion that 
when a soil showed as little as '01 per cent of 
phosphoric acid soluble in a 1 per cent solution of 
citric acid, it might be regarded as in need of 
phosphatic manuring.] 
In the process of 'soil analysis as generally 
carried out the potash determined is such as 
dissolves in strong hydrochleric acid. Some of 
this may be in a condition us to be readily avail- 
lable as plant food, but most of it is certauily not. 
Further more the determination has not even the 
merit of being an absolute determitiatiou, as la 
the case of the ordinary phosphoric acid determi- 
nation, in which case the results represent the 
total percentage present in the soil. 
In the case of ordinary p'otash determination, 
the quantity can scarcely ever present the total 
potash contained in the soil, for the great majority 
of soils contain potash in the form of silicates, 
which are not; decomposed even by the strongest 
hydrochloric acid, in the Rottamstead soils, for 
instance, there is considerably more than 1 per 
cent of total potash present, only a fraction of 
which is disolved by hydrochloric acid. 
If the proportion'dissolved by.hydrochloric acid 
in any given soil were constant, the determi- 
nations might possess some arbitrary value ; but 
even this is not the case. The quantity dissolved 
depends upon the fineness to which the soil is 
ground, the strength and quantity of the acid 
luken, the length of time during which it is heated, 
and a number of other considerations which will 
at once occur to the practical analyst. A know- 
ledge, therefore, of the proportion of potash 
soluble in hydrochloric acid is in most cases of 
small value. 
I vt-nture to think however, that the determi- 
nation of the p)tash dissolved by a dilute solution 
of citric acid is possessed of much more value. 
(^Dr. Dyer then furnishes another corapreliensive 
series "of analysis to ]>rove his deduction.) In 
the case of potash it might be said that when the 
ovailable (citric-acid-soluble) potash is shown to 
'^ro'pical Agriculturist" 519 
be as high as "01 per cent, it may be asf.umed as 
probable that the direct application of potash salts 
will be unnecessary, 
I have not attempted in this paper to deal with 
the question of nitrogen. The total determination 
of nitrogen in a soil, which, with present methods, 
is simple enough, gives, no doubt, an indication 
of its potential fertility as regards this element, 
but it gives no indication ns to the immediate 
abundance of nitrogen which may be regarded 
as present plant-food. A determination of the 
nitrogen existing as nitrate would probably be 
the nearest measure that we could get of the 
nitrogen-fertility of the soil at the moment, but 
nitrates are so e.isily washed from the soil that 
the quantity present today may be very much 
less than the quantity presennt yesterday, if the 
soil be an open one and a heavy shower has inter- 
vened. 
What is most important as regards nitrogen 
would be to know the total nitrate- producing 
power of the soil, a power depending not merely 
upon the quantity and nature ot the nitrogen 
naturally accumulated in tlie soil, but, firstly, 
upon the presence and multiplicity ot those 
various micro-organisms on whose actioh depends 
the transformation, through many stages, of 
insoluble vegetable nitrogeri compounds on the 
one hand into soluble nitrates on the other ; and, 
secondly, on the chemicai and physical conditions of 
the soil itself, such as scarcity or abundance of 
lime, densiiy, porosity, climate, drainage, aspect, 
and a number of other circumstance- ; and here 
analysis can do little to help us. Since nitrogen, 
however, on land that is in healthj- physical 
condition, is not only freely nitrified, but is also, 
when unas-imilated, freely washed away in drain- 
age, it may be generally assumed that all soils 
under old arable cultivation require a reinforce- 
ment of nitrogen in some form or other, and it is 
much more often a matter of doubt (which the 
chemist is often asked to solve) whether a soil 
needs a dressing of sulphate or rnuriate of potash, 
than wliether it requires a dressing of nitrate or 
of ammonia salts. 
THE EFFECT OF GRAFl'INQ. 
The extent of the influence of the stock on 
the scion has hitherto been but imperfectly 
understood,- non-scientific cultivators have been 
at a disadvantage in not having any definite 
data to go upon in their practical operations. 
The following authoritative statement iti the 
Oardeners' Chronicle is therefore welcome, as to 
a great extent, settling points which have up 
till now remained in dispute. 
"It must be remembered that the theory of 
the graft has been completely altered during 
the present decade. The orthodox opinion on 
the subject implied that hereditary variation 
was purely of sexual origiti, and in a text- 
book which wa.s published less than seven years 
ago, one of the mo^t disiinguished European 
botanists stated that the graft is a vuliiable 
means of fixing and conserving nil the variations 
introduced into the cuit^ryo, becuu-e the pro- 
cess itself does not produce (he slightest vari- 
ation. 
