APraL 1, 1898.] SupiRement to the “ Troincal Agriculturist}'' 
729 
relation to the amount of potassium provided. P. 
Wagner has made the interesting observation that 
the potassium may be partly replaced^ by sodium. 
The exact value of magnesium is not yet well 
understood, but it appears to be of importance 
in the formation of the nitrogenous substances 
of seeds, ns in these considerable quantities of 
magnesium phosphate occur. 
Nitrogen is, of course, an indispensable plant- 
food, for it is an essential consfituent of albumen. 
In addition to the quantities of mineral 
substances required by plants to enable them to 
grow healthily, further quantities are found to be 
essential to satisfy what has been termed 
(though not very aptly) the mineral hunger of 
the plant. This is explanied by an example. E. 
Wolff found that for the production of parts of 
the oat plant (dried), ‘5 parts of phosphoric 
acid were necessary when the remaining mineral 
substances were supplied in excess. The fol- 
lowing quantities of mineral matter were found 
to be essential for 100 parts of cats; Piiosphoric 
acid, '5; Potash, ’8 ; lime -2-5 ; magnesia, "2; and 
sulphuric acid, ’2; making a total of 1'95. There 
is, however, no oat plant which contains so little 
ns 1 ’96 per cent of mineral substances, the mini- 
mum being '3 percent. The difference (1 ’05) is 
the measure of what has been called the “ mineral 
hunger,” and represents the mineral matter which 
does not perform any special function. The ex- 
cess may be supplied in the form of some in- 
different substance, as silica. This observation is 
said to be of considerable interest to the farmer, 
for it shows that it is not economical to manure 
crops with pure substances. 
It has been found, unfortunattely, that the 
chemical analysis of a soil is of little use as a 
guide unless accompanied by a “mechanical ana- 
lysis,” or a determination of finely-divided con- 
stituents present in the soil, which form the only 
part that presents a sufficiently large surface for 
the exercise of the solvent action of water and 
its dissolved carbonic acid. There is one case in 
which chemical analysis is said to be of the great- 
est importance, viz., when there are traces only 
of some necessary elements in the soil. Here there 
is a question of a need for a manure containing 
this substance. If on the other hand large quan- 
tiles are present, it does not follow that there is a 
sufficiency in the soil even when the latter is 
in a satisfactory state of division, for the substance 
may be present in an insoluble refractorjy form. 
This is commonly the case with nitrogen, which 
exists in the soil chiefly in the form of a mixture 
of indefinite nitrogenous substances known ns 
humus, or mould. These substances sometimes 
easily give up their nitrogen to plants, but in 
other cases are very refractory. The uncertainty 
as to their action is indeed so great that 
certain peaty soils are known w'hich consist 
almost entirely of humus, but contain nevertheless 
an insufficiency of available nitrogen. 
Phosphoric acid affords another illustration. 
The soluble phosphoric acid of the manure is ab- 
sorbed by the soil as dicalcic phosphate, which 
is comparatively easily soluble in the soil water. 
With time, however, it may change in the soil 
to the insoluble tricalcium phosphate or even to 
iron or aluminium phosphates, which are still less 
soluble. 
In the case of calcium, chemical analysis has been 
found to be of considerable service in determining 
what manuring is required, since calcium is 
chiefly valuable in the form of carbonate or 
humate, and the-e are easily estimated in the 
soil. 
Since theii the direct method of soil-analysis 
is an insufficient guide to manuring, it is fortu- 
nate that chemists have been able to develops 
successfully an indirect method. This is the 
cultivation method, by which plants are allowed to 
grow in the soil under examination, after taking 
care to provide a sufficiency of all plant-food 
stuffs excej)t the one, e.g., phosphoric acid, 
whose presence in available form is being tested. 
The plants are then analysed, and the results 
compared with the analyses of the same plants 
grown on soils provided with all the necessary 
plant- food stuffs. As an important result of the 
method it has been found that different plants 
take up very different quantities of the same 
mineral substances. On this is largely based the 
system of rotation of crops, where the second 
crop is so chosen that it chiefly removes the 
ingredients of the soil which have been left by the 
preceding crop. 
With the aid of the cultivation method it has 
also been possible to draw up the following table, 
which represents the relative values of the differ- 
ent nitrogen compounds for plant-food: — 
Nitrogen of Saltpetre ... 100 
„ „ Ammonia ... 86-90 
„ „ Albumen ... 60 
This table may be made use of in determining the 
nitrogen value of a manure. 
The cultivation method may be used for testing 
the value of manures of all kinds. Thus it was 
by a few cultivation experiments that Wagner 
in Darmstadt first showed the very great value 
for agricultural purposes of the “Thomas” Slag, 
produced as a bye-product in the manufacture of 
iron by the basic process of Thomas-Gilchrist. 
The million tons of phosphate meal annually pro- 
duced in Germany is now wholly utilised by the 
agriculturist, and its preparation for the farmer 
has become an important off-shoot of the iron 
indu.stry. 
Prof, Maercker’s address then goes onto deal 
with other points which we may refer to 
in a future issue. Those we have noticed are 
undoubtedly of interest and value, and deserve to 
be carefully noted by our readers. 
NOTES FOR CATTLE OWNERS IN CEYLON.=:‘ 
This is the title of a little pamphlet of 16 
pages by Mr. C. AV, Sturgess, Colonial A''eteri» 
nary Surgeon. The headings of the different chap- 
ters us given in the Tal)le of Contents are : Food, 
AVater, Shelter, Signs of Health and Disease, Breed- 
ing and Real ing. Prevention of Disease, Contagious 
Diseases, Nursing, and a List of simple A’'eterinarj'' 
Medicines. AVhat will be most interesting to cattle 
owners is, of course, the treatment recom- 
mended for the various forms of cattle disease 
that occur in the Island. The author, Iiow- 
ever, refers only to the two common forms of 
* Printed at the Goveiument Printing Press, 
