24 
BULLETIN" 114, 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 pious 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 
404. 62 
38.72 
1.24s 
.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 
.088 
1.753 
625.37 
25.01 
665.03 
26.60 
1.637 
1.926 
.077 
726. 68 
24.22 
736.03 
24.53 
2.175 
.073 
2.028 
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 1| 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. 
