24 



BULLETIN" 174, U. S. DEPARTMENT OF AGRICULTURE. 



figures show a close relation to the cross section of the plows, as given 

 in the upper half of the same table. The irregularities already noted 

 in the case of the 20 and 25 horsepower tractors also occur. In five 

 out of the seven classes of tractors there is shown a slight decrease in 

 the amount of work done per hour by the tractors which have been 

 used two seasons. 



Table XIV. — Average area of the cross section of plows drawn and area plowed per hour 

 in North Dakota by different sizes of farm engines. 



Plows and plowing. 



Drawbar rating of engine (horsepower). 



30 



40 



Area of cross section of plows drawn: 

 First year — 



Per engine square inch. . 



Per drawbar horsepower do 



Second year — 



Per engine do 



Per drawbar horsepower do 



Area plowed per hour: 



For 1-year-old tractors — 



Per engine acres. . 



Per drawbar horsepower do 



For 2-year-old tractors— 



Per engine do 



Per drawbar horsepower do 



447.21 

 37.27 



464. 62 

 38.72 



1.248 

 .104 



1.386 

 .116 



474. 86 

 31.66 



459.43 

 30.60 



1.410 

 .094 



1.350 

 .090 



474. 69 

 23.73 



455. 81 

 22.79 



1.405 

 .070 



1.327 

 .066 



716. 86 

 32.58 



662. 72 

 30.12 



1.946 



1.753 

 .0S0 



625. 37 

 25.01 



665.03 

 26.60 



1.637 

 .065 



1.926 

 .077 



726. 68 

 24.22 



736. 03 

 24.53 



2.175 

 .073 



2.028 

 .068 



908.92 

 22.72 



748. 68 

 18.71 



2.374 

 .059 



2.165 

 .054 



While these averages are in harmony with the other figures regard- 

 ing the operating factors, attention is invited to the fact that an 

 average amount of work for a tractor in North Dakota may be either 

 a great deal more or a great deal less than for some other section where 

 conditions are different. There are so many factors which influence 

 the amount of work which can be accomplished with a tractor that 

 average figures are of use only in the section from which they were 

 obtained or under conditions almost identical. The figures for North 

 Dakota represent, for the most part, extremely favorable conditions 

 for tractor plowing. 



BREAKING. 



The conditions which obtain in breaking sod, are even more various 

 and produce wider variations in the amount of work done than those 

 which are found in plowing. 



The number of reports on breaking received from any one section 

 was too small to merit publication of the averages obtained from them. 

 In North Dakota, where the sod is broken with comparative ease and 

 where there is little brush to interfere, the average acreage broken per 

 hour varied from about eight-tenths of an acre for the 12-horsepower 

 tractors to \\ acres for the 30 and 40 horsepower tractors. 



Many men report the same acreage per day in breaking as for plow- 

 ing, as the breaking is not done so deep as plowing and the tractor 

 wheels find a better grip. In most cases, however, the acreage broken 

 per day is only about two-thirds of that plowed. 



