36 
THIRTEENTH REPORT. 
SOIL AND SOIL PROBLEMS FROM THE STANDPOINT OF 
PHYSICIST. 
J. A. JEFFERY. 
Fig. 1. 
So long as soils produce moderate to large crop yields, tlieir produc- 
tiveness does not arouse much concern, it is not taken seriously. When 
the yields reach a point so low as to be unprofitable or but moderately 
profitable, the question “why” is asked. Not long ago this question was 
thought not so hard to answer. It was generally conceded that the 
supply of plant food was being exhausted. The remedy was as simple 
and about as correct as the answer: — The supply should be replenished. 
For a time the replenishing worked, and it does yet under certain 
conditions. Under other conditions it does not. The result is that 
other “wliys” are introduced until at the present time the whole thing 
is given another name. It is a soil problem, and a many sided one. 
It was thought at one time that the solution of the problem lay with 
the chemist, but he failed to produce a satisfactory solution, and as 
the problem is further studied it is suspected that the botanist, the 
bacteriologist, the soil physicist and the practical crop and fruit man 
may each be required to assist not only to determine the causes, but 
also to decide upon the theory and the facts of the remedy. 
