DRAFT OF PLOWS 213 



The angle of the share with the landside is an important 

 factor, and must be adapted to different soils. For instance, 

 in Colorado, in dry alfalfa fields, a plow with an acute angle 

 will dodge the roots, while one having a share at nearly a right 

 angle to the landside will chip up the baked ground and break 

 or cut the roots cleanly. In mellow loam the slanting cut must 

 be used. In this case the soil is not firm enough to hold the 

 roots taut, hence they double over and clog a share which is 

 set at a wide angle. 



Soils differ greatly in their cohesive properties. The average 

 draft of nine plows in an old English test, for a furrow 5x9 

 inches in each of five different soils, was as follows: Loamy 

 sand, 227 Ibs.; sandy loam, 250 Ibs.; moory soil, 280 Ibs.; 

 strong loam, 440 Ibs.; blue clay, 661 Ibs.; a difference between 

 extremes of 194 per cent. An average of fifty-seven of Pro- 

 fessor Sanborn's tests on varying soils in Missouri in 1888 

 gave a draft of 5.26 Ibs. per square inch in area of the cross 

 section of the furrow slice turned. In Utah, several years 

 later, the same number of similar tests averaged 5.94 Ibs. per 

 inch. Four hundred and fifty tests in an Illinois cornfield aver- 

 aged 4.76 Ibs. In Missouri 500 Ibs. turned a 7 x 16 inch furrow 

 on timothy. Over 600 Ibs. was needed for the same furrow in 

 red clover in Utah, and still more for alfalfa. Seven trials on 

 clover gave an average of 6.47 Ibs. per inch, and six on oat 

 stubble gave 4.68 Ibs. At the Winnipeg motor contests of 

 1909 and 1910 the average draft per 14-inch bottom, going three 

 one half to four inches deep in virgin gumbo sod, was 770 Ibs. 

 and 795 Ibs., respectively, or 13.75 to 16.3 Ibs. per inch. These 

 and other figures might be cited to illustrate the difference 

 in draft due to soil conditions, but even relative figures are 

 very few. 



It may be said that for ordinary depths and widths of plowing 

 the draft per square inch of cross-section ranges from about 

 three pounds in sandy soil to seven or eight in clay, six or 

 seven in tame clover sod, and ten to fifteen pounds in virgin 



