PURCHASE AND USE OF FERTILIZERS 339 



Apply 100 pounds per acre on poor soils, 150 pounds on good 

 soils, as a top dressing in the spring after the grass or crop is well 

 started. For ordinary field crops, since nitrogen is so expensive, 

 the increase in yield may not pay for nitrogen used in fertilizer. 



Crops grown in the early spring, such as early spring forage, 

 or spring wheat, oats, etc., may be unable to secure sufficient nitro- 

 gen from the soil to permit of rapid and maximum development. 



The agencies which change organic into active nitrogen may 

 not be sufficiently active to produce a sufficient supply of active 

 nitrogen. Hence an application of active nitrogen in the form of 

 nitrate of soda may cause great gains to take place. Some crops, 

 as tomatoes, cabbage, potatoes, etc., must be grown and harvested 

 early, in order to be highly profitable. Hence their growth must 

 be forced at a time when the natural agencies are not very active. 



According to bulletins of the New Jersey Experiment Station, 

 the use of 150 pounds per acre of nitrate of soda has increased the 

 wheat crop 9 bushels per acre. Early tomatoes were increased in 

 value 50 per cent, by 150 to 250 pounds, early cabbage 40 to 80 

 per cent, by 400 pounds, musk melons doubled in value by 200 

 pounds. 



Quantity of Fertilizer. The applications of different quanti- 

 ties of the same fertilizer follows the law of diminishing returns. 

 That is, the increase produced by each successive increment of fer- 

 tilizer diminishes as the quantity of fertilizer increases. Thus the 

 cost of the increment increases with the quantity of fertilizer. 

 The fertilizer is profitable up to a certain point, after which the 

 value of the increase is not equal to the cost of the additional 

 amount of fertilizer. The most profitable quantity depends upon 

 the character of the soil, the kind of crop and its value, and 

 climatic conditions. The more valuable the crop, the larger the 

 quantity of fertilizer which may be profitable. 



As an illustration, we will cite the experiments conducted for 



four years by the New York (Geneva) Experiment Station 1 to 



ascertain the most profitable quantity of fertilizer for potatoes. 



The fertilizer used contained 8 per cent, available phosphoric acid, 



1 Bulletin 187. 



