ABSORPTIVE POWER OF CEREALS 295 



of nitrogen, and hence nitrogen is the fertilizer consti- 

 tuent that usually gives best results, and should be 

 added in a soluble form. Wheat, in particular, needs 

 a large amount of soluble nitrogen early in its spring 

 growth. Since it is a delicate feeder, it does best after a 

 cultivated crop or a fallow, by which the nitrogen has 

 been converted into a soluble form. Oats can make 

 better use of the soil fertility and does not require 

 so much manuring. Maize is a very coarse feeder, and, 

 while it removes a very large quantity of plant-food 

 from the soil, it does not require that these be added 

 in a soluble form. Farm manure and other slowly acting 

 manures may well be applied for the maize crop. The 

 long growing period required by the maize plant gives 

 it opportunity to utilize the nitrogen as it becomes 

 available during the summer, when ammonification and 

 nitrification are active. Phosphorus is the substance 

 usually most needed by maize. 



153. Grass crops. Grasses, when in meadow or in 

 pasture, are greatly benefited by manures. They are 

 less vigorous feeders than the cereals, have shorter 

 roots, and, when left down for more than one year, the 

 lack of aeration in the soil causes decomposition to 

 decrease. There is usually a more active fixation of 

 nitrogen in grass lands than in cultivated lands, but this 

 becomes available very slowly. 



Different soils and different climatic conditions 

 necessitate different methods of manuring for grass. 

 Farm manures may well be applied to meadows in all 

 situations, while the use of nitrogen is generally profi- 

 table. 



