1 



1740 SOIL PHYSICS, CHEMISTRY AND MICROBIOLOGY 



of soil was dug up and replaced in its i)ositioii at every station and a check 

 plot of xuidisturbed soil was also set aside. It was therefore possible to 

 compare at each station i) the natural undisturbed field soil; 2) the natural 

 field soil after having been disturbed; 3) the soils from the other two ex- 

 periment stations. When 7 years later the present writer attacked the pro- 

 blem of the effects of climate on soils, the above plots appeared to provide 

 admirable material for study in this connection, and it was decided to 

 subject them to a ph3'sical, chemical and bacteriological investigation. 



The most striking change undergone by the transported soils is in 

 their appearance. Shaw and Walters originally described the Cali- 

 fornian soil as " Sacramento silt loam ", the Kansas soil as a "dark heavy 

 loam" and the Mar^daad soil as a « Light yellow clay >'. During the period 

 which has elapsed since the soils were moved, their colour has changed 

 markedly, Kansas and Mar3dand soils in California becoming of a much 

 deeper reddish colour, and Kansas and Californian soils bleaching to a 

 light or yellowish clay in Maryland. Soils brought to California have also 

 increased their hygroscopic coefficient, their moisture equivalent (i) and 

 their wilting point. 



The bacterial investigations show that in general the munbers of 

 bacteria increase when arid soils are put tmder more humid conditions 

 and decrease when humid soils are brought to a drier climate. Ammoni- 

 fication and nitrogen fixation vary in a similar favshion and so does nitri- 

 fication with certain forms of nitrogen. The destruction of cellulose, on the 

 other hand, varies inversely with the bacterial numbers. 



Chemical analyses reveal marked changes in the acid soluble con- 

 stituents of soils due to climatic effects. For example the Californian soil 

 increases in lime in Kansas and Maryland (particularly at the latter 

 station) and loses in iron. Though difficult to generalise, the tendency 

 is for soils to increase in iron and decrease in alumina when j^laced under 

 arid conditions and viceversa. Phenomenal losses in certain constituents 

 seem to have occurred in some soils even when the latter were not moved, 

 the Marjdand soil losing enormous quantities of magnesia in the given 

 period. With regard to the total water soluble constituents, these in- 

 crease considerably when the Californian soil is moved to Kansas or 

 Maryland and the same occurs with Maryland soil when moved to Kansas 

 or California. 



vSome of the effects noted are difficult to explain in the light of our 

 present knowledge, but the causes of other effects stand out quite clearly. 

 For example, it appears that the total internal surface of soils per unit 

 of dry weight increases with the degree of aridit}' of the climate, and this 

 exercises an important influence on the hygroscopicity, moisture equi- 

 valent, wilting point, tenacity, absorbing ])ower and many other physi- 

 cal characteristics of a given soil. With the chemical data the causes for 

 the changes are more difficult to define because of the great irregularit}' 

 of some of the results obtained. Ikit they indicate clearly that profound 



(i) See R. Oct. loifi, No. 1050. {F-d. 



