148 TILTH AND TILLAGE 



ment follows the common plow, and cuts a thin, deep gash in the 

 bottom of the furrow; thus loosening the subsoil without mixing 

 it with the surface soil. Subsoiling is not a general practice in 

 humid farming, since results do not seem to warrant the extra 

 expense, except under unusual conditions. The subsoiler should 

 never be used in light, sandy loams, sand or gravelly soils. 



Deep tilling through the use of other plows designed for this 

 purpose generally do not give the returns above the extra cost to 

 encourage this practice. 



Fro. 85. " Striking out a land " with a two-bottom gang plow. 



Dynamiting Soils. Dynamite has been used in some places 

 to break up and loosen impervious subsoils to facilitate the entrance 

 of air, water and roots. Though it proves a good practice, when 

 necessary in tree planting, its general use is still an open question. 2 



More About Plows and Plowing. Special plows are designed 

 for hillside plowing (Fig. 84). The bottoms of the walking types 

 swivel for right- and left-hand furrows, and the sulky types consist 



2 Subsoiling, deep tilling, and soil dynamiting are all operations that 

 increase the expense of production over that of ordinary plowing. Experi- 

 ments conducted in both dry-land and humid farming all lead to the conclusion 

 that yields cannot be increased nor the effect of drought overcome by tillage 

 below the depth of ordinary plowing. Jour. Agril. Research, Sept. 9, 1918. 



