6 BULLETIN 627, U. S. DEPARTMENT OF AGRICULTURE. 
machine drawn by three horses and the eight-foot outfit with four 
horses is 5 cents per acre, or about 18 per cent. Where the seven- 
foot binder with three horses is used the cost per acre for horse-labor 
is only 1 cent greater than where the eight-foot binder and four 
horses are used. In other words, horse-labor is utilized almost as 
economically on a seven-foot binder drawn by three horses as on an 
eight-foot outfit drawn by four horses, but the cost of man-labor is 
greater on the smaller machine. The charge per acre with the seven- 
foot binder is exactly the same with either three or four horses when 
the values of man- and horse-labor bear the relation which they do 
in this table, as the cost for horse-labor is less where only three 
horses are used, while that for man-labor is correspondingly lower 
where four horses are used. This point is well worth considering 
where hired help is scarce and extra horses are available. 
TasLE II.—Labor cost of cutting one acre of wheat with binders of different 
sizes and with varying numbers of horses, man-labor at $2 per day, and horse- 
labor at $1.20 per day of 10 hours (based on figures in Table J). 
Cost per acre. 
Width of cut and number of horses. He 
Total labor.| Man-labor. | Horse-labor. 
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57 -17 
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In actual practice it often is possible to hire horses from neighbors 
as low as 75 cents each per day and board, many farmers being will- 
ing to hire their horses out at a very low figure in addition to their 
board, when they have no work for them. The cost of horse-labor per 
hour therefore is frequently less with a hired horse under these condi- 
tions than where the horse is owned and maintained during the 
entire year. 
INTERES? AND DEPRECIATION. 
In this bulletin the interest charges on the various machines have 
been computed in all cases at 6 per cent on one-half the cost of such 
equipment, which figure represents the average investment. Many 
men fail to consider interest charges at all, whereas others allow in- 
terest on the first cost of their equipment for each year of its life. 
This is incorrect, as the value of the equipment decreases each year of 
its life, and if charges are made against it for depreciation it is 
obvious that interest should not be charged against these amounts 
during subsequent seasons. Assuming that the equipment is worth- 
Jess at the end of its life (that is, ignoring its junk value), the aver- 
age amount invested will be 50 per cent of its first cost, and the 
