12 BULLETIN 757, U. S. DEPARTMENT OF AGRICULTURE. 
USE OF MACHINERY. 
The use of machinery on North Dakota farms is costly in the ag- 
gregate, but when reduced to the acre basis the cost is comparatively 
small, owing to the fact that the large implements cover large acre- 
ages. The cost of operation of machinery may be classified under 
the three main headings: Depreciation, interest on investment, and 
repairs. A fourth group might be included which would cover stor- — 
age, Insurance, and taxes on machinery, but these amount to com- 
paratively little. 
The depreciation may be determined by estimating the life of the 
various implements; interest on investment in machinery is calcu- 
lated on the value at the beginning of the year and not on the first 
cost, except during the first year; repairs cover necessary outlay for 
replacing broken or worn parts, paint, oil, etc. The average depre- 
ciation of farm implements in North Dakota varies considerably, de- 
Fig. 6.—Thrashing in the field from the shock. 
pending upon the care and use of the various machines. The average 
life of implements is 12 years; in other words, the average annual 
cost for machinery depreciation is approximately 8 per cent of the 
new value. 
Repairs amount to approximately 6.5 per cent of the cost value 
of all farm implements on the average, although there is a wide 
variation in the amount of repairs required for different implements. 
For further details concerning the use of farm machinery, see page 17. 
THRASHING. 
Thrashing is a comparatively large factor in the production of 
grain, since large amounts of both man labor and horse labor are 
required in a very short time, the greater part of the thrashing in 
the State being done in less than 30 days, after about September 10. 
Most of the thrashing rigs are composed of a steam traction engine 
and separator with self-feeder and blower. 
The usual thrashing crew (fig. 6) consists of about 20 men and 
22 horses as follows: Eight to 10 men with teams hauling grain from 
