172 FOOD FOR PLANTS 



its roots may reach out for the water of the soil 

 which holds in solution mineral plant-food. 



Since nitrogen is supplied in many different forms, 

 it at once becomes a question as to which of these is 

 most efficient in crop production. Far too little 

 attention has been given to this important question. 

 Too often a certain material has been chosen because 

 there was among farmers a general impression that 

 this particular material was better than some other, 

 when, as a matter of fact, there was no scientific basis 

 for such conclusion. As an example, nitrogen from 

 organic sources has been preferred by many because 

 it was believed that organic matter thus supplied 

 would be of great value in improving the physical 

 condition of the soil, but in making this choice farm- 

 ers overlooked the possibility of using a more 

 readily-available material which would increase the 

 crop residues sufficiently to more than make up for 

 the small amount of organic matter contained in the 

 few hundred pounds of dried blood, fish or tankage. 

 Also, there is a widespread impression that the loss 

 of nitrogen is greater when Nitrate is used, than 

 when organic nitrogen is used. But experiments 

 both in this country and abroad show beyond a doubt 

 that the crop yields and the percentage of nitrogen 

 recovered in the crop were greater (and hence the 

 loss must have been less) when Nitrate was used 

 than when organic sources of nitrogen were used. 



The question of availability of nitrogenous ferti- 

 lizers began to receive serious consideration at sev- 

 eral of the leading European experiment stations 

 some 30 years ago and much valuable information 

 has been accumulated by these stations. 



