62 BULLETIN 1371, U. S. DEPARTMENT OF AGRICULTURE 
study of the soil-management methods practiced by successful and 
leading farmers, especially in the older farming sections, clearly 
shows that the maintenance of soil productivity is accomplished 
most efficiently, not by rigid or fixed systems of cropping, fertilizing, 
and liming, but by systems that are more or less flexible. In rational 
farming, soil, crop, topographic and economic conditions on prob- 
ably the majority of farms compel variations in rotations and in 
the use of soil-improvement materials. In fact, because of these 
conditions, there are only a comparatively few farms, taking the 
country at large, which can be successfully divided into a certain 
number of fields or cropping units to accommodate a single, fixed 
rotation. 3 This is quite evident, for uniformity of soil as regards 
kind or producing power is rather unusual. A rotation best suited for 
a field of low-producing sand is seldom suited to a field of productive 
silt loam; a hillside field subject to soil erosion calls for a different 
management as regards rotation than a field on a flat area; and so on. 
The primary question that confronts a practical farmer who farms 
more or less with livestock does not concern rotation so much a^ it 
does the acreage of crops necessary to best meet his feeding require- 
ments. On the other hand, the truck grower ,is concerned primarily 
with the question of the crops best suited to meet the market condi- 
tions. In either case the cropping problem resolves itself into two 
parts: (1) The growing of the desired crops in a manner, or in dif- 
ferent rotations, best suited to the soil and crop conditions, and, 
(2) the dove-tailing, so to speak, of the different rotations so as to 
enable the farmer to realize annually the required acreage of each 
crop he desires to grow. 
In the light of economic and rational fertilizer practice, the appli- 
cations of chemical fertilizers made on the experimental plots are to 
be regarded as heavy or excessive, and the fertilizers in themselves 
" unbalanced." Nevertheless, the applications selected for compa- 
rable yields have given, in the majority of cases, most favorable re- 
sults. Over against the effects of these heavy applications have 
been weighed the effects of fixed rotations, whose effects in any 
particular test can not be regarded as being determined by material 
quantity, as in case of the fertilizers. 
It is not possible to know with any degree of certainty what the 
results would have been if, in some of the experiments, the rotation 
had been altered or changed, or if in all the experiments the applica- 
tions of chemical fertilizer were modified to conform to the modern 
ideas of fertilizer practice, which are generally recognized as being 
the more scientific. That such modifications, or breaks in the rigid- 
ity of the experimental plans, would have resulted in higher average 
yields seems quite certain, for the higher average yields obtained by 
leading farmers carry considerable significance. 
The average yield of wheat on the fertilized plot 2-C, in rotation 
on the Agdell field at Rothamsted, for example, is 32.5 bushels, 
while the average yield for England and Wales is 31.7 bushels (16, 
p. 56). This means that the average }~ield of wheat on many farms 
in England and Wales must be much higher than that on the Agdell 
field; and the chances are that these high yields are not obtained as 
* A fixed rotation may be defined as a rotation in which the crops recur at regular intervals and which 
occupies a fixed number of years; for example, a four -year rotation of corn, oats, wheat, and clover. 
■ I 
