CURRENT LITERATURE 
BOOK REVIEWS 
Soil fertility 
RUuSSELL' has added to the monographs on biological chemistry a volume 
on soil conditions and plant growth. The table of contents by chapters 
gives an idea of the scope of the work: (1) historical and introduction, (2) con- 
and its interpretation. There is also an appendix on methods of soil analysis. 
The book contains a bibliography of 323 citations and an index of two pages. 
The treatment of the subject deserves characterization as critical, broad, 
and in the main unbiased. The soil is considered as an environmental factor 
of the plant, as the title implies, and not merely from the side of chemical and 
physical analysis. Great emphasis is laid upon the application of BLACKMAN’s 
idea of limiting factors, a principle the importance of which in biological 
problems it is hard to overrate. In this connection the author cites data 
to show that addition of mineral salts has little or no effect on yield if another 
factor, such as water supply, is already a limiting factor. RUSSELL con- 
cludes that soil toxins play no part in the fertility of well cultivated and 
drained agricultural lands, but admits that they at formed and may remain 
for some time in poorly drained and “exhausted” land. Some will question 
whether he has sufficient data for such a sweeping statement in the face of 
some of the experiments of our Bureau of Soils. Many will commend the 
caution with which he uses the term “available nutrients," < or fi his terminology 
“available food,” also his lack of readiness to distinguish sharply between 
“essential” mineral salts and other _ and even organic compounds that 
increase yield. 
In spite of the breadth of treatment that characterizes the monograph 
in the main, and the evident attempt of the author to give every soil factor 
affecting growth and yield its proper emphasis, it is evident that he turns 
more often than our present knowledge will insure to deficiencies of some 
mineral nutrient as the limiting factor. For instance, he attributes increased 
yields due to heating soils or treating them with poisons to the increase in 
ammonium salts due to differential killing of soil organisms, thus furnishing a 
greater nitrogen supply. It is true that there is some questionable evidence 
* RUSSELL, Epwarp J. (Rothamsted Experimental Farm), Soil conditions and — 
plant growth. viii+168. London: Longmans, Green & Co. 1912. 
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