Tilth and Tillage of the Soil 



1767 



larger the food supply with which they are in touch. On light sandy 

 soil, deep plowing must be accompanied by the generous use of organic 

 manures. 



In the humid section of the country, where rainfall is over twenty 

 inches, the undisturbed subsoil, especially on heavy or poorly drained 

 soils, is likely to be infertile for a time after being brought to the surface, 

 owing to its poor sanitary condition. In that section it is therefore unwise 

 to turn too much fresh soil directly on top in any one season. Usually, 

 it is advisable to increase the depth of plowing gradually at the rate of 

 cne half to one inch per year. This is best done in the fall. 



The deeper the soil is plowed, the more thoroughly it is pulverized. 



Fig. 96. — An example of good plowing. The soil is a sandy loam. As good plowing 

 may be accomplished by the use of a team and a walking plow as with this tractor- 

 drawn gang 



Other things being equal, better results are obtained from the same draft 

 in deep than in shallow plowing. 



Draft of plow. — Tests by Professor C. A. O'Cock, of the University of 

 Wisconsin, warrant the following conclusions concerning the operation of 

 the ordinary moldboard plow : 



First, the draft per inch cross section of furrow cut increases with the 

 increased width. 



Second, the draft per inch cross section of furrow cut decreases as the 

 depth is increased. 



Third, the sharper the curve of the moldboard, the greater is the draft 

 of the plow. Thus, a fallow-ground moldboard pulls harder than the sod 

 type of the same size. 



