52 



BULLETIN 907, U. S. DEPARTMENT OF AGRICULTURE. 



Effect of amount of work done per year on cost oj using tractors. — 

 Table 39 shows the cost per day and per acre of plowing with the 

 2-plow machines, classified according to number of days of work 

 during the year. Table 40 gives similar information for the 3-plow 

 tractors. Annual depreciation, repairs, and interest charges did not 

 increase in proportion to the amount of work done for either size of 

 machine, and consequently the daily costs of these items were least 

 for the machines which did the greatest amount of work. 



For each size the average daily charge for depreciation, interest, 

 and repairs on the tractors which were used 50 days or more during 

 the year was less than a third of that for machines which were used 

 less than 20 days, and the cost per acre of power for plowing done by 

 the machines which did over 50 days' work was less than a half the 

 cost for those which did less than 20 days' work during the year. 

 Such differences are reflected directly in the cost per acre or per 

 bushel of producing crops and show how the man whose farm is large 

 and so organized that he obtains large use from his equipment can 

 produce at low cost. 



These figures do not indicate, however, that the farmer should 

 endeavor to use his tractor as many days during the year as possible 

 simply for the sake of reducing the cost per day of operating it. 

 Even though the cost per day decreases rapidly with increased use, 

 the total cost per year must increase. For instance, the cost per 

 day of power for plowing with the 2-plow tractors which were used 

 20 to 30 days during the year was $13.45. On the average these 

 machines did approximately 25 days of work during the year and 

 the total cost per year of use was $325 to $350. The cost per day of 

 use of the 2-plow machines which did from 40 to 50 days of work 

 during the year was only $10.81, but the total cost per year was 

 $475 to $500. 



These figures further indicate that, since the number of days of 

 work has only a slight effect upon the total annual charges for depre- 

 ciation, interest, and repairs, the tractor owner need consider only 

 the cost of fuel and oil when deciding whether or not to use his 

 machine for operations where its use is of doubtful value. 



Table 39. — Effect of number oj days of work per year on cost of using 2-plow tractors for 



plowing. 





Number 



of 

 tractors. 



Annual cost. 



Daily cost 

 (depre- 



Cost for plowing. 



Days of work per 

 year. 



Depre- 

 ciation. 



Interest. 



Repair 



and 

 upkeep. 



Total. 



ciation, 

 interest, 



and 

 repairs). 



Per day. 



Per acre. 





37 

 41 

 54 

 25 

 17 



$150 

 158 

 168 



167 

 195 



$34 

 35 

 34 

 33 

 35 



$30 

 37 

 39 

 61 

 32 



$214 

 230 

 241 

 261 

 262 



$14. 50 

 8.90 

 6.97 

 6.08 

 4.60 



$19. 14 

 13.45 

 11.49 

 10.81 

 8.55 



$3.00 



20 to 29.9 



2.24 



30 to 39.9 



1.76 



40 to 49.9 



1.76 



50 and over 



1.26 







