188 SOILS AND PLANT LIFE 



of strong, vigorous germination may be safely planted 

 earlier than that whose vitality is low, because if bad 

 weather follows such seed will not decay so readily. 



(e) Insects. These are commonly most destructive 

 early in the season ; hence late planted corn is less liable 

 to be injured by them. In sod ground, believed to be 

 badly infested by them, this is to be kept constantly in 

 mind. 



The general rule is to plant corn as early as the tempera- 

 ture and other soil conditions will permit. It has been 

 quite conclusively shown that the highest yields are se- 

 cured by early planting, owing, doubtless, to the greater 

 length of the growing season. 



126. The Depth of Planting. — The general rule as to 

 depth of planting is to plant as shallow as the conditions 

 which govern germination will permit; that is, the seed 

 should be put into the ground only so deep as is necessary 

 in order to secure all three of the conditions upon which 

 germination depends, viz. : moisture, oxygen and suitable 

 temperature. (Section 46.) 



The average depth of planting is perhaps about two and 

 one half inches. As previously stated (Exercise 27), 

 we do not try to control the depth of the root systems by 

 the depth of planting, since this is impossible. In any 

 given case, the depth of planting is determined chiefly 

 by the following conditions : 



(1) Soil Texture and Structure. — In loose sandy soil, 

 it is necessary to plant deep in order to reach moisture. 

 On the other hand, this would not do ordinarily in a heavy 

 clay soil as the seed would be deprived of oxygen, and 

 moreover, after a heavy rain such soil has a tendency 

 to puddle and bake, which prevents the sprouts from 

 pushing through. 



