COMMERCIAL FERTILIZERS 



99 



and potash. There are several grades of this meal, those 

 that contain the largest proportion of hulls being the least 

 valuable. This meal cannot be used by plants until it has 

 decayed. It is more suitable, therefore, for crops that 

 occupy the land in the warm weather than for very early 

 crops which make their growth in cool weather. 



Nitrate of soda. Nitrate of soda is a fertilizer with 

 more than twice as much nitrogen as cotton-seed meal. 

 It costs more than twice as 

 much per ton, but does not 

 need to be used in such large 

 amounts. It is brought by 

 ships from South America, 

 for in that hot country the 

 nitrogen has already been 

 changed into the form of 

 a nitrate, ready to be used 

 by plants at once. 



When nitrate of soda is 

 sown broadcast on the sur- 

 face of the ground where 

 young wheat or oat plants 

 are growing, the moisture of 

 the soil dissolves the ferti- 

 lizer and carries it down- 

 ward to the roots of plants. 

 Within a week after this fertilizer is sown, wheat and oat 

 plants become much greener and more luxuriant. It is 

 especially suitable for plants that make their growth 

 during the cool months (wheat, oats, etc.) and for vege- 



FIG. 64. CORN FROM EQUAL AREAS 

 On right, no nitrogen in fertilizer; on 

 left, fertilized with 240 pounds of 

 nitrate of soda per acre. Yield per 

 acre without nitrogen, 3.2 tons; with 

 nitrate of soda, 6. 7 tons. 



