﻿16 



BULLETIN 3, U. 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. — J. normal day's toork tvith a spring-tooth harrow, giving the average acreages 

 reported for the widths most frequently used and adjustments for other vjidths. 



[Net hours in the field, 9.65.] 





Width of harrow. 



On freshly plowed land. 



On well-packed land. 



Num- 























ber of 





Most 



Har- 







Allow- 



Har- 







Allow- 



horses. 



Range. 



rowed 



Number 



Adjusted 



ance for 



rowed 



Number 



Adjusted 



ance for 





width. 



per 



averaged. 



acreage. 



each foot 



per 



averaged. 



acreage. 



each foot 







day. 







in width. 



day. 







in width. 





Feet. 



Feet. 



Acres. 







Acres. 



Acres. 







Acres. 



2 



4-8 



6 



7.4 



180 



6.5 



0.60 



8.6 



169 



7.5 



0.70 



3 



6-10 



6 



8.2 



120 



7.4 



.70 



10.2 



113 



9.2 



.80 



4 



6-12 



8 



13.1 



22 



11.8 



.75 



14.8 



23 



13.3 



.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 five horse units do not increase in 



