NOVEMBER 19, 1903] 
NATURE 
5g 
much is known of the origin of the nitrates in the 
soil from the results obtained by Warington at Roth- 
amsted and by King in Wisconsin to allow one to 
suppose their amount would ever approximate to a 
constant even for the same soil, yet nitrates are 
perhaps the dominant factor in plant nutrition. 
The phosphoric acid and potash figures are a little 
more in harmony, and we have examined those relating 
to the same four soils with the following results :— 
| 
| Phosphoric acid. Parts per million 
| 
Highest Lowest Mean 
Windsor Sand 12°88 2°65 6°21 + 0°25 
Norfolk Sand 16°52 1°71 6°33 40°19 
Leonardtown Loam 16°5 29 7°16 + 0°26 
Sassafras Loam ... 21°45 2°24 7:61 + 0°30 
woe a Saeed 
Potassium. Parts per million 
| Highest | Lowest Mean 
ae =| sere 
Windsor Sand. ....... | 46:11 | 10°90 | 24°27 + 1°02 
Norfolk Sand... ... | 44°9 11°64 | 22°19 + 0749 
Leonardtown Loam ... 51°66 10°08 | 23°61 + 0°65 
Sassafras Loam ... | 46°8 7:94 -|. 24°22 + 0°63 
| 
These numbers would indicate variation round a 
mean which is practically the same for all soils as 
regards potash, but which as regards phosphoric acid 
has a different value for different types of soil, 
approaching one value for sands and another for 
loams. This agrees with the probability that the 
potash compounds are of the same type in all soils, 
whereas several distinct compounds of phosphoric acid 
must exist in relative proportions varying with the 
type of soil, and we surmise that these mean results 
might be correlated with the amount and solubility of 
the compounds appropriate to the various types of soil 
were more data available. But for the purpose of the 
argument we are not concerned with mean results, but 
with individual ‘soils; the authors rest their case on 
the constancy of composition of the soil solution, and 
their own figures show variations too wide and too 
numerous to fall within any allowable limits. It may 
be true enough that the variations exhibited cannot 
be correlated with the known productiveness of the 
soils, but that is only a proof of the ineffectiveness 
of the analysis of the aqueous extract of a soil, not 
of the non-existence of a chemical soil factor in crop 
production. Indeed, it is not quite easy to see what 
the numbers do represent; the volume of water em- 
ployed is so small, and the time of extraction so short, 
that they cannot stand either for the solution existing 
in the soil or for the material which water could extract 
during the growth of a crop. Some analyses are given 
of the actual solution extracted from various soils; ‘all 
that can be said of them here is that they show no 
more constancy of composition than the laboratory 
extracts, nor do the old analyses of the drainage waters 
at Rothamsted lend any more support to the idea of 
a soil solution of constant composition. 
Though Dr. Whitney’s main argument is thus 
hardly tenable on his own showing, certain side issues 
are worth a little notice. Dealing with the action of 
fertilisers, he notices that, while the wheat crop on the 
best fertilised plot at Rothamsted averages about 33 
bushels, on the plot which has been unmanured for 
sixty years it has fallen to 12 or 13 bushels. Yet on 
the similarly unmanured plot in the Agdell field, where 
NO. 1777, VOL. 69] 
the wheat is grown once every four years in rotation 
with roots, barley, and clover or fallow, but little 
falling off is apparent. Hence he concludes that, in 
virtue of the rotation, the fertility of the Agdell field 
is unimpaired, whereas in the continuous wheat field 
“‘ the decrease can be ascribed only to some physical 
change in the soil, to some chemical change other than 
the actual loss of plant food taken up by the crops.” 
But when any other crop on the unmanured plots in 
Agdell field is considered, the decline in fertility is 
enormous; roots and clover only yield minimal crops ; 
so far as they are concerned the cultivation of the soil 
involved in the rotation has been quite unable to main- 
tain the fertility. The wheat, with its powerful root 
system, holds up better, but its production is falling 
steadily; it is important to see how long it will be 
maintained, though it need never be expected to fall 
to the level of the continuous wheat, because the land 
is practically only cropped every other year, so trifling 
has the output of roots become. 
When Dr. Whitney says that there are few instances 
showing that a given fertiliser is required by a certain 
soil, and that generally fertilisers have no consistent 
or continuous effect, he ignores too much the results 
both of experiment and experience in countries like our, 
own. In England a body of knowledge has been 
accumulated concerning the requirements of particular 
soils and crops for specific fertilisers such as is hardly 
possible in America, where much of the land has only 
recently been brought under intensive cultivatior in- 
volving the use of purchased manures. | 
In another place Dr. Whitney says ‘‘ the beneficial 
effect of fallowing is not due to an accumulation of 
soluble plant food in the soil.’’ Not wholly due, 
perhaps, but King’s investigations show what a, 
powerful factor the accumulated nitrates become, and 
a recent discussion of the Rothamsted results shows 
that after a wet autumn, to wash out the nitrates 
formed during the summer fallow, the benefit of 
fallowing disappears almost entirely, whereas after a 
dry autumn and early winter it produces an increase 
of crop of nearly 50 per cent. 
Suggestive as Dr. Whitney’s memoir must be to all 
agricultural chemists, we thus do not consider that the 
main theory it propounds possesses any permanent 
value. We should be sorry if we have failed to appreci- 
ate the argument properly, but it is not always easy to 
follow, the text being somewhat deficient in sequence 
and orderly arrangement; indeed, we are disposed to 
think that had the question been set out a little more 
nakedly at the outset, and the demonstration mar- 
shalled with more precision, a somewhat different con- 
clusion would have been reached by the authors. The 
fundamental thesis is unimpeachable, that water con- 
tent and temperature are the main factors in crop 
production, but the chemical composition of the soil 
is also a large factor, though its magnitude and re- 
lation to the other physical factors do not yet admit of 
complete determination. A. Di i. 
THE ‘SURVEY OF ‘INDIA, 
VOLUME of extracts from narrative reports of! 
the Survey of India, for the season 1900-1901 * 
has recently been issued. These extracts, which used 
to be published in the same volume as the annual re- 
port, are now issued separately. The reports selected 
for publication show admirably the range of the oper- 
ations of the Survey of India. They deal with seven 
subjects. 
(1) Zincography.—For certain classés of maps repro- 
duction from zinc is eminently suitable, and owing to 
the introduction of thin zinc plates, difficulties of 
1 Pp. 68. (Calcutta: Government Printing Office, 1903.) Price 2s. 3¢- 
