8 BULLETIN 320, U. S. DEPARTMENT OF AGRICULTURE. 
YIELD FACTORS OTHER THAN TILLAGE. 
In such a study as this it is impossible to measure the effect of 
tillage in terms of yield. This is true, for the reason that tillage is 
only one of the many factors which have to do with yield, and while 
yields are, for the most part, given in connection with these studies, 
it is firmly believed that the yields are far more closely related to 
the inherent fertility of the soil and to the general farm practices 
than to tillage. 
The variations in yields, both regional and on individual farms 
in a given region, show but scant correlation to variations in tillage 
practice. There is, however, a striking correlation between yields 
and type of farming. Yields in the main in the different regions are 
in inverse ratio to the area of improved land which is in intertilled 
crops. In some of the regions surveyed other factors enter which 
affect crop yields, and in those regions this relation between the yield 
of corn and the area of intertilled crops does not exist. Such con- 
ditions are found in Scotland County, X. C, and Hartford County, 
Conn., where large quantities of commercial fertilizer are used, and 
in Augusta County, Va., and Bradford County, Pa., where the land 
is rolling or rough and corn is grown mostly on the bottom lands 
with hay and pasture on the hillsides. However, notwithstanding 
these factors, when the regions included in this study are arranged 
in order of rank in yield, the first 10 show but 29.5 per cent of 
improved land in intertilled crops, with a yield of 45.4 bushels of 
corn per acre, while the remainder show an average of 52 per cent 
of the improved land intertilled, with a yield of only 27.4 bushels of 
corn per acre* Again, it is well known that in a large measure hay 
and pasture enter into the rotation to supplement intertilled crops. 
In other words, far more than for tillage, yields of corn tend to vary 
directly with the extent to which crops adding organic matter to the 
soil — hay and pasture crops — enter into the rotation. 
ECONOMIC FACTORS INFLUENCING TILLAGE. 
In Table I, as in all the general tables, the areas surveyed are 
placed in the order of bushel yield of corn per acre, starting with 
the area having the highest yield. The only direct bearing of Tables 
II and III on tillage is in showing the acreage of cultivated land and 
of intertilled crops per horse for the regions studied. The other mat- 
ter presented, however, does have an important indirect bearing on 
the subject of tillage, in that it gives the reader a general knowledge 
of existing farm conditions. This information is necessary to a 
proper interpretation of the purely tillage data presented in subse- 
quent tables. 
