54 SOUTHERN FIELD CROPS 



of November may be regarded as a generally satisfactory 

 date for sowing wheat. 



55. Drilling versus broadcast sowing. Experiments in 

 the principal wheat-growing states show a larger yield from 



FIG. 20. DOUBLE-DISK GKAIN DRILL. 



drilling wheat by the use of a grain drill (Fig. 20), sowing 

 the seed in rows, 6, 7, or 8 inches apart, than from sowing 

 broadcast. The advantages of drilling are the following : 



(1) Usually a somewhat larger yield. 



(2) Planting at a more uniform depth and hence greater 

 uniformity in the ripening of the plants. 



(3) Slightly increased protection from winter-killing 

 through heaving, that is, the lifting of the young plants 

 above the surface by the expansion of the moisture in the 

 soil when it freezes ; the plants growing in the slight de- 

 pression left by the drill are in the position where there is 



