26 BULLETIN 1447, U. S. DEPARTMENT OF AGRICULTURE 
The purchase of a tractor should imply the need for additional 
power or the substitution of tractors for horses and consequently 
a reduction in the number of horses kept. 
It should be kept in mind that the cost of operating tractors and 
using horses varies as changes occur in the prices of work stock, 
feed, tractors, fuel, oil, etc., and that, notwithstanding the higher 
cost of tractor motive power during the years of the study, many 
farmers preferred the tractor to horses. This is particularly true 
on the larger farms where large acreages needed to be tended in a 
comparatively short time. 
Some of the advantages and disadvantages of tractors are not 
easy of measurement, but, in general, the opinions of these tractor 
owners as given on page 13 indicate that the tractor has a number 
of real advantages on many of these farms. 
SEASONAL DISTRIBUTION OF HORSE AND TRACTOR WORK 
On these farms where wheat production is the principal enterprise 
ihe greatest demand for horse work occurs in March and April, 
when the land is being plowed and disked, and again in July and 
August during the harvest season. The number of horses that must 
be kept is governed largely by the demand for horse work at these 
two periods of the year. The farms in this area are, for the most 
part, well adapted to the use of tractors which, after their purchase, 
should displace a considerable number of horses. 
The distribution of horse work on a certain Sherman County 
wheat farm in 1922 before the purchase of a tractor is shown in 
Figure 7. The owner of this farm exchanged the use of his combine 
for the use of a neighbor’s tractor in harvest so that his combine 
was drawn by a tractor. The amount of horse work that would have 
been required had the power for harvesting been supplied by horses 
has been estimated, as well as the number of horses required to 
operate the farm had all of the work been done with horses. On 
this basis it is assumed that 24 horses would have been sufficient 
to operate this farm and the total horse hours would have amounted 
to 17,272, or 720 hours per horse per year. 
It will be seen that the “ peak ” of horse work occurred during the 
latter part of March and the harvest period of July. The horse 
work performed in March consisted of disking unplowed land and 
plowing in the preparation of summer fallow land. During the last 
10-day period of March a total of 1,472 horse hours was devoted to 
plowing. Plowing was started March 16. The work in April was 
a continuation of disking unplowed land and plowing. Plowing 
continued until May 12, from which time until harvest started on 
July 10, the horse work consisted principally of weeding. 
Harvesting was at its height during the middle 10-day period of 
July, and, with wheat hauling for that period, amounted to a total of 
1,592 hours of horse work. The harvest work (hauling) ended 
August 26. The horse work in September and October consisted 
principally of drilling, together with a limited amount of weeding 
and harrowing in the preparation of a suitable seed bed. 
In April of 1923 a 40-drawbar horsepower tractor was purchased. 
The distribution of the horse and tractor hours after the purchase 
