344 SOUTHERN FIELD CROPS 



as well as extreme shallowness, is to be avoided. Plowing 

 too deep may bring to the surface much of the subsoil, 

 where, for a year or two, it remains infertile and subject 

 to baking or clod-forming. Moreover, the cost of very 

 deep plowing is excessive. A depth of 6 to 8 inches may 

 be regarded as unusually good preparation; this depth 

 should be attained only gradually, that is, by plowing 

 each year only about an inch deeper than the year before. 

 By a gradual and judicious increase in depth, a few farmers 

 have advantageously stirred their soil to even a greater 

 depth than 6 to 8 inches. For very deep plowing the disk 

 plow is a favorite implement (Fig. 80). 



When plowing is early, or several months before the 

 time of planting the seed, the depth may well be greater 

 than in late plowing. This is because the earlier plowing 

 permits the upturned subsoil to be improved by the ac- 

 tion of freezes and of the air, and because the deeper layer 

 of stirred soil requires a longer time to settle to that degree 

 of compactness most favorable to the germination of seeds 

 and the growth of plant roots. 



Even when deep preparation fails to increase the yield 

 the first year, an increase is apt to result in succeeding 

 years. The aim of the cotton grower should be gradually 

 to deepen the layer of plowed soil. 



316. Subsoiling. — This term means the loosening of 

 the subsoil without bringing it to the surface. It is usually 

 accomphshed by first employing an ordinary turn-plow, 

 and then in its furrow running a special subsoil plow (Fig. 

 78). This latter plow has no moldboard, and merely 

 loosens the subsoil, without displacing it. 



Subsoiling is a means of suddenly increasing the depth 



