ENRICHING SOIL COMMERCIAL RESOURCES 101 



160. Again, no results can be obtained from 

 the addition of one element unless the other 

 two are present in sufficient quantity. In gen- 

 eral, therefore, it is safer to apply complete 

 fertilizers. 



161. Yet, in some cases, it is unwise to 

 apply complete fertilizers. This is particularly 

 true of the application of nitrogen. The growth 

 may already be so heavy that the addition of 

 nitrogen would cause an overgrowth, and yet 

 the plants may need fertilizing. This danger 

 of too much growth is greatest with fruit 

 plants (114). 



162. If nitrogen conduces especially to leaf 

 growth (134), then it must be the element 

 which is most important in the fertilizing of 

 the vegetables which are grown for their leaves 

 or succulent stalks, as rhubarb, cabbage, let- 

 tuce, spinach, asparagus ; and it is also very 

 important in the growing of hay and succulent 

 fodder. 



163. Nitrogen leaches rapidly, especially if 

 applied in the form of nitrate of soda or sulfate 

 of ammonia. It is, therefore, advisable to ap- 

 ply it in the spring ; and when used in liberal 

 amounts, it should be applied at intervals, and 

 not all at one time. 



164. Phosphoric acid and potash, even if 

 soluble, do not leach badly, as a rule, because 



