8 BULLETIN 1458, U. S. DEPARTMENT OF AGRICULTURE 
comparison with the natural processes which have brought the fertility of the 
soil to its present state of dynamic equilibrium with its climatic environment 
(he DG). 
A consideration of the crop yield statistics of the various farming 
regions of the United States indicates that most of the increases in 
acre-yield in the United States occurred in the older farming regions 
east of the Mississippi River. ‘This point was graphically illustrated 
by Professor Warren in a study published in 1914 (72, p. 191). 
The greater changes that have occurred in the yield level of these 
crops in certain of the older farming regions of the United States 
are somewhat concealed in these national trends. These regional 
changes will be discussed later. 
INCREASE IN VOLUME OF PRODUCTION RESULTING FROM 
RISING LEVEL OF ACRE YIELDS 
Although it is recognized that a great part? of the increasing 
volume of production of our staple food and feed crops has, of 
course, been the result of expansion onto new lands, nevertheless, the 
effect of the rising acre-yield level in increasing our volume of agri- 
cultural production has probably been consistently underestimated. 
The changes in the combined acreage and total production, during 
the last four decades, for corn, wheat, oats, and potatoes, are indi- 
TREND IN COMBINED ACREAGE AND TOTAL PRODUCTION 
OF CORN, WHEAT, OATS, AND POTATOES 
United States, 1885-89 — 1920-24 
Acreage = 
Total Production iN 
1885-89 
1890-94 
1895-99 
1900-04 
1905-09 
1910-14 
1915-19 
Fic. 3.—The curves show that the total volume of production of these crops increased 
much more than the total acreage in these crops as a result of the rising acre-yields. 
The spread between the curves measures the increasing productivity of the area in 
these crops during the period 
cated in Figure 3. During that period the combined acreage of 
these crops was expanded about 52 per cent and the total production 
of these crops increased 77 per cent. The gradual spread between 
the two curves is a reflection of the increasing productivity of the 
area in these crops during the period of 40 years. 
