46 
BULLETIX 1348, U. S. DEPAETMEXT OF AGEICrLTTEE 
made when preparing to work, availability when wanted, comfort 
of the operator, range of speeds available for specific kinds of work, 
reserve power available for emergencies, etc. For the small job, 
requiring httle power ^vith a resulting small cost, convenience or 
ease of operation probably is of greatest importance, but for the 
larger operations economy in getting the work done should be the 
principal deciding factor in the choice of power. 
Fig. 50.— Crop acres per farm worker based on 1920 census 
The following outhne compares some of the principal advantages 
and disadvantages of the dinerent kinds of power as they are now 
used on farms : 
ADVANTAGES AND DISADVANTAGES OF DIFFERENT KINDS OF POWER USED ON 
FARMS 
ADVANTAGES 
Animals : 
Great reserve power for emer- 
gencies and temporary over- 
loads. 
Use feed produced largeh' on the 
farm. 
Great flexibility of size of power 
unit. 
Adapted to practically all draft 
work. 
Fairly good traction in wet or 
loose ground. 
Lay up of one animal does not 
lay up entire power plant. 
Can be reproduced on farm. 
Do not require constant attention 
in guiding. 
Relatively cheap type of power 
in areas where a surplus of 
both grain and roughage is pro- 
duced. 
DISADVANTAGES 
Animals : 
Require feed and care vrhen not 
working. 
Work at heavy loads limited to 
short periods. 
Require frequent resting periods. 
Can not work efficiently in hot or 
sultry weather. 
Working speed limited. 
Not efficient for stationary work. 
Relatively large amount of time 
required to feed, harness, and 
care for. 
Require a relatively large space 
for shelter and feed storage. 
Un^^ieldy when used in large 
units. 
Require the products from one- 
fourth of all crop land to feed 
them. 
