16 BULLETIN 218, U. S. DEPARTMENT OF AGRICULTURE. 
than when it followed oats. In every year except 1914 the yield has 
been higher following either wheat or oats when the land was spring 
plowed than when it was fall plowed. 
The yields on disked corn ground have averaged higher than those 
on the stubble of any small grain plowed in the fall and approximately 
the' same as on the stubble of wheat and corn plowed in the spring. 
The highest average yields have been produced by summer tillage. 
When cost of production is taken into consideration, it is seen in the 
last part of Table VII that the higher yields from summer tillage and 
green manure have been obtained at a cost proportionately greater 
than the increase in yields. 
The only method showing production at a loss is that of green 
manuring. The smallest profit, SI. 92 per acre, has been by summer 
tillage, which has giv*en the highest yield. Disked corn ground, 
owing both to high yield and low cost, shows the greatest average 
profit, $6.87 per acre. The average profit from spring plowing has 
been $5.02 and from fall plowing $3.74. 
DICKINSON FIELD STATION. 
The soil at the field station at Dickinson, N. Dak., is somewhat 
lacking in uniformity. It is characterized as a sandy clay loam to a 
depth of approximately 5 feet. Below this depth is a lighter soil 
which in some cases becomes very sandy or pure sand. The soil has 
the capacity to retain a large supply of water and to give up a large 
proportion of it to the crop. This, together with the depth to which 
a crop may feed, makes it possible to store in this soil an exception- 
ally large quantity of water that can be recovered by the crop. 
The results of six years are available for study from Dickinson 
Station. The crop in 1912 was destroyed by hail shortly before 
maturity and is not included in computing averages. The crop of 
1914 was damaged at least 50 per cent by hail. 
The average annual yields have ranged from 8.9 bushels in 1911 
to 67.8 bushels in 1909. The averages for the six years by different 
methods of cultivation and cropping range from 29.6 bushels on 
fall-plowed oat ground to 49.9 bushels by summer tillage. While 
this is a comparatively wide range in results from different methods, 
it is apparent that the ability of a method to increase yields is de- 
pendent upon the season. It will be noted that in 1909, a season of 
heavy production, there were comparatively small differences in 
yield from different methods. In 1911, when the seasonal rainfall 
was very deficient, summer tillage and rye as green manure gave 
fair yields, while other methods were nearly or quite failures. During 
the years of average climatic conditions the differences in yields 
have not been so extreme, but with few exceptions summer tillage, 
green manuring, and disking corn ground have consistently given 
the best yields. The highest average, 49.9 bushels, for the five years 
