126 



WHEAT CULTURE 



most, and many farmers in New York and Ohio use only acid phos- 

 phate, at the rate of from 100 to 300 pounds per acre. It is generally 

 considered better practice, however, to use a complete fertilizer, 

 which means all three elements. A common fertilizer for wheat con- 

 tains 3 per cent nitrogen, 8 per cent phosphoric acid, and 5 per cent 

 potash; such a formula is commonly known as a 3-8-5 fertilizer 

 (seep. 37). 



Minerals Used in Early Growth. One reason which helps to 

 explain why wheat responds so well to fertilizer is that it requires 

 elements in the early part of the season when the available supply in 

 the soil is limited. As the summer advances and the soil becomes 

 warm, plant-food becomes more available, but studies at the Minne- 

 sota Station show that the wheat plant takes up about 85 per cent of 

 its food supply from the soil by the time it is half-grown, while dur- 

 ing the latter half of its growth wheat is building up its starch and 

 cellulose material which is taken largely from the air. The follow- 

 ing data on the wheat plant are reported in Minnesota Bulletin 29 : 



Composition of Wheat at Different Dates 



Time of Sowing Winter Wheat. It is generally agreed that 

 the sowing should be early enough to give a good root growth before 

 the soil freezes. This means six to eight weeks before freezing. If 

 sown too early, however, the stems are apt to grow too large and to be 

 killed back to the crown by freezing. This causes a second set of 

 tillers to come out in the spring and these are never as strong as the 

 first stems. Also, when the Hessian fly is present, sowing must be a 

 little late to avoid the fly (p. 139). 



Time of Sowing Spring Wheat. The very earliest sowing pos- 

 sible is considered best for spring wheat. (1) The long period of 



