16 
BULLETIN 3, IT. S. DEPARTMENT OF AGRICULTURE. 
in all respects to Table VI for spike-tooth, harrows. The duty of any 
team and width, can readily be found by inspection. In using these 
tables it should be borne in mind that the widths most commonly 
used have doubtless been found from experience to be the most 
efficient, so that the factors for other widths, if required in practice, 
would doubtless be underloads in the smaller sizes and overloads in 
the larger sizes. 
Table VII. — A normal day's ivorh with a spring -tooth harrow, giving the average acreages 
reported for the widths most frequently used and adjustments for other widths. 
[Net hours in the field, 9.65.] 
Width of harrow. On freshly plowed land. 
On well-packed land. 
Num- 
ber of 
horses. 
Range. 
width - day. 
Number 
averaged. 
Adjusted 
acreage. 
Allow- 
ance for 
each foot 
in width. 
Har- 
rowed 
per 
day. 
Number 
averaged. 
Adjusted 
acreage. 
Allow- 
ance for 
each foot 
in width. 
2 
3 
4 
Feet. 
4-8 
6-10 
6-12 
Feet. 1 Acres. 
6 i 7.4 
6 ! 8.2 
8 13. 1 
180 
120 
22 
6.5 
7.4 
11.8 
Acres. 
0.60 
.70 
. 75 
Acres. 
8.6 
10.2 
14.8 
169 
113 
23 
7. 5 
9.2 
13.3 
Acres. 
0.70 
.80 
.90 
Compilation of the data for disk harrows showed it to be an imple- 
ment of very heavy draft, since 52 per cent of farmers find it neces- 
sary to use four horses on an implement which is not frequently found 
in widths over 8 feet. This width is one-half that of the largest 
practicable size in the spring-tooth type and one-fourth that for the 
largest spike-tooth harrow. The relative draft per foot of these 
implements appears to be in the proportion of 4, 2, and 1. About the 
same proportion, 23 per cent, that report using two horses with the 
spring and spike tooth harrows use three horses in disking. The 
8-foot width is somewhat more generally used than the 6-foot width 
and 75 per cent of the disk harrows reported are from 6 to 8 feet wide. 
The 16-inch disk is most generally used; 17 per cent have the 18-inch 
type, and a somewhat smaller proportion use the 12, 14, and 20 
inch sizes. Well-packed land is about 20 per cent easier to disk 
than freshly plowed land from the standpoint of acreage covered in 
a day. When the power is increased, the average acreage per day 
increases, while the acres per horse tends slightly to decrease and 
the acres per foot of width increase, indicating an overload by this 
implement with the smaller numbers of horses. The area disked 
by 3-horse teams does not increase over that by 2-horse teams in 
the proportion that the acreage for four horses increases over that for 
two horses. The same variation appears as between the 4-horse and 
5-horse teams when compared with the difference between 4-horse 
and 6-horse teams. This is in part explained by the fact that the 
widths reported for the three and R\e horse units do not increase in 
