MN 
2 BULLETIN 1458, U. S. DEPARTMENT OF AGRICULTURE 
How this has colored our thought may be gathered from the pop- 
ular notions, often encountered, that the productivity of our older 
farming areas has been deciining and that our volume of agricul- 
tural production was being maintained or increased solely as a 
result of new virgin lands brought into use for crop production. 
THE AWAKENING NATIONAL INTEREST IN THE SOIL-PRODUCTIVITY PROBLEM 
We are beginning to realize, however, that. our land area in rela- 
tion to prospective requirements is limited and that our area of arable 
land is still more limited. It is true that even at the present time 
our total crep area is less than half of that estimated as physically 
capable of being used for crop production (4, p. 427). Much of the 
remaining area, however, includes land which may never be eco- 
nomically reclaimed. Practically all of our good arable land avail- 
able for use without reclamation is contained in our present crop 
area. Further expansion of our crop acreage will be on lands poorer 
or more expensive to reclaim than those already in cultivation. 
The realization of this condition is the basis for the recent interest 
in our population growth and the trend in the volume of our food 
production. | 
The rapidity and the magnitude of the westward expansion of our 
agricultural area in the past has tended to eclipse the changes that 
have been taking place in the older agricultural areas of the United 
States. As long as the supply of free or very cheap virgin lands 
held out there seemed to be very little reason for giving much thought 
to the period that our agriculture must pass into sooner or later if 
our growth is to continue. Considered from a national viewpoint, 
Edwin G. Nourse has well expressed this idea in the following: 
But the bloom of youth is quick to pass, and, after a brief but riotous heyday 
of virgin fertility, even so new a land as America is rapidly passing into the 
ageless period of permanent use and productivity wherein true costs of produc- 
tion begin to figure potently, and agriculture passes onto an industrial basis 
like any other human occupation of using the materials and forces of nature 
under an administration shrewdly cognizant of their scarcity value and toward 
the production of the maximum market. surplus (8, p. 474). 
With the greater part of our available agricultural area already in 
use and a population that is growing steadily, the problem of pro- 
ductivity and soil fertility in their relation to our future food supply 
is now coming to the fore as one of the most important phases of the 
study of land utilization. 
HAVE YIELDS PER ACRE DECLINED? 
Is it true that we have been increasing our agricultural production 
solely through the expansion of our agricultural area? Have the 
farmers of the older farming sections as a whole continued the 
extractive methods of soil exploitation characteristic of the early 
period of American agriculture? Has there been no progress and 
taking up of scientific methods of soil management in the older 
farming areas of our country? From many sources in the past we 
have heard of and even seen in various localities of the East the 
abandonment of land formerly used for crop production. Has this 
condition been general and has it occurred as a result of steadily 
declining crop yields?) Why should yields in the old agricultural 
