The Function of Manures and Fertilizers 25 



the case with nitrogen and phosphoric acid. All of these 

 forms are soluble, and can be readily absorbed. 



DANGER OF LOSS FROM THE USE OF SOLUBLE PLANT-FOOD 



The fact that the artificial fertilizer-products con- 

 tain the constituents in such forms and combinations 

 as to enable them to feed the plant immediately, also 

 presents some disadvantages from the standpoint of 

 economical use. This is particularly true in the case 

 of nitrogen, for nitrogen, when applied in the form of 

 nitrate, in which form it is taken up by the plant, does 

 not combine to make insoluble compounds, but remains 

 freely soluble. A great waste, therefore, may ensue from 

 leaching into the lower layers of the soil and beyond the 

 roots of plants, or into the drains, and the plant-food be 

 carried away, unless care is exercised both as to the amount 

 and the method of application. With soluble phosphates, 

 the danger of loss is much less than with nitrogen. If 

 these are applied in too large quantities to meet the needs 

 of the plants, or under improper conditions, their tend- 

 ency is not to remain soluble, but to revert to their 

 original and insoluble form. The main fact, however, 

 is that in artificial fertilizers we may have the constit- 

 uents in distinct and separate forms, which permits the 

 feeding of the plant, rather than the feeding of the soil ; 

 and this is usually, and must necessarily be, the case when 

 natural manure products serve as the entire, source of the 

 added fertility. For example, nitrogen may be supplied 

 in artificial fertilizers in three forms, each form being dis- 

 tinct and separate from the other, and each giving up its ni- 

 trogen to the plant at a different time, supplying its needs as 

 required by growth, in which case the danger of loss is small. 



