206 Fertilizers 



compounds and is perfectly soluble when in a form useful 

 to plants, is liable to loss from leaching. Furthermore, 

 the mineral elements are relatively cheap, while the nitro- 

 gen is relatively expensive, and thus the economical use 

 of this expensive element, nitrogen, is dependent to a 

 large degree upon the abundance of the mineral elements 

 in the soil. It is, therefore, advocated that for all crops 

 and for all soils that are in a good state of cultivation, a 

 reasonable excess of phosphoric acid and potash shall be 

 applied, sufficient to more than satisfy the maximum needs 

 of any crop, and that the nitrogen be applied in active 

 forms, as nitrate or ammonia, and in such quantities and at 

 such times as will insure the minimum loss of the element 

 and the maximum development of the plant. The supply 

 of the mineral elements may be drawn from the cheaper 

 materials, as ground bone, tankage, ground phosphates 

 and iron phosphates, as their tendency is to improve in 

 character ; potash may come from the crude salts. Nitro- 

 gen should be applied chiefly as nitrate of soda, because in 

 this form it is immediately useful, and thus may be applied 

 in fractional amounts, and at such times as to best meet 

 the needs of the plant at its different stages of growth, with 

 a reasonable certainty of a maximum use by the plants. 

 Thus no unknown conditions of availability are involved, 

 and when the nitrogen is so applied, the danger of loss by 

 leaching, which would exist if it were all applied at one 

 time, is obviated. 



This method also possesses many advantages, particu- 

 larly where the " intensive " system is practiced, though 

 it is also useful in quickly building up wornout soils, or 

 those naturally poor, because in any case these must be 

 provided with liberal supplies of the minerals, and when 

 these only are applied, the immediate outlay is far less 



