NITRIFICATION 1 27 



148. Deep and Shallow Plowing and Nitrification. 



— In a rich prairie soil nitrification goes on very 

 rapidly. This is one reason why shallow plowing on 

 new breaking gives better results than deep plowing. 

 Deep plowing at first causes nitrification to take place 

 to such an extent that the crop is overstimulated in 

 growth. Deep plowing and thorough cultivation aid 

 nitrification. The longer a soil has been cultivated, 

 the deeper and more thorough must be the cultivation. 



149. Spring and Fall Plowing, and Nitrification. 



— Early fall plowing leaves more available nitrogen 

 at the disposal of the crop than late fall plowing. 

 Nitrification takes place only near the surface. Hence 

 when late spring plowing is practiced there is brought 

 to the surface raw nitrogen, while the available 

 nitrogen has been plowed under, and is beyond the 

 reach of the young plants when they require the most 

 help in obtaining food. The various methods of 

 cultivation as deep and shallow plowing, spring 

 and fall plowing, and surface cultivation have as much 

 influence upon the available nitrogen supply of crops 

 as upon the water supply. The saying that cultiva- 

 tion makes plant food available is parti cularly true of 

 the element nitrogen, the supply of which is capable 

 of being increased or decreased to a greater extent 

 than that of anv other element. 



