6 BULLETIN 757, U. S. DEPARTMENT OF AGRICULTURE. 
the State showing a difference of approximately 6 inches in annual 
precipitation. While the difference in average yield per acre between 
different parts of the State is not wide, the difference in rainfall 
causes a very marked increase in risk involved in crop production, 
which is reflected in the price of land. A less important cause is 
the quality of land, as that in the Red River Valley is somewhat 
more fertile and, being generally heavier in texture, retains moisture 
better than the soils of the western part of the State. 
Fic. 3.—Acreage of crops (North Dakota, 1891-1916). 
The value of farm buildings varies according to size of farm and 
decreases somewhat on farms of the same size from east to west. 
The latter fact is due to the earlier development of eastern North 
Dakota as well as to the greater certainty of production in this 
region. The average building investment of farms of 320 acres or - 
under over the State is approximately $3,000. The value of build- 
ings per farm of 321 to 640 acres averages approximately $5,000. 
Farms averaging 1,000 acres, and ranging from 641 to 2,560 acres, 
have buildings averaging $5,200 in value. 
Work stock in North Dakota consists chiefly of horses, and the 
average value is $155 each. Farms of 640 acres utilize approxi- 
mately 13 horses each. Each horse covers the equivalent of 38 acres _ 
of crops. (See page 15.) 
