4 Chemical Composition and Commercial Value of 



and not been found to realize the expectations raised, superphos- 

 phate and similar phosphatic manures have maintained a firm 

 hold in the good opinion of the agriculturist. Far be it from 

 me to undervalue the great utility of Peruvian guano, nitrate of 

 soda, and nitrogenous manures. These are excellent fertilizers 

 for wheat and corn-crops in general ; but considering the cir- 

 cumstance that a good root-crop lies at the very foundation of an 

 improved system of agriculture, and that this crop is more 

 signally benefited by phosphates than by any other fertilizing 

 constituent, I believe the farmer is right in attaching the highest 

 importance to phosphatic manures. At all events, he has 

 found by experience that in most cases in which it is deemed 

 desirable to make up a deficiency of yard-manure, it pays better 

 to purchase superphosphate and similar manures for the root- 

 crop than to buy nitrogenous manures for the white crops. 



It is certainly remarkable that whilst the direct application to 

 the land of nitrogenous constituents has been by some considered 

 useful only in special cases, and by others superfluous or even 

 undesirable, nobody has ever expressed any doubt as regards the 

 economical benefits that generally attend the use of phosphoric 

 acid ; whilst nitrogenous manures in the case of some crops, 

 such as peas and beans and clover, have been found even to be 

 injurious, every kind of produce has been more or less benefited 

 by the direct application of phosphates in an available condition. 

 Whereas ammoniacal salts and other purely nitrogenous fertilizers, 

 when applied alone to swedes, turnips, and probably other root- 

 crops, have, generally speaking, failed to increase the produce, 

 the exclusive use of soluble phosphates has, in almost every in- 

 stance, largely benefited these crops. 



Again, we can increase the proportion of nitrogenous consti- 

 tuents in the soil by other means than by their direct application 

 in the shape of manure. Thus, after a good crop of clover, I 

 have found that the amount of nitrogenous matters in the soil is 

 very much larger than it was before the clover. If, therefore, 

 we can succeed in growing a good crop of clover, we at the 

 same time enrich the land with nitrogenous matters, and provide 

 for the succeeding white crop that kind of food for which it 

 appears to be specially grateful. The fact that a good crop of 

 wheat may be confidently anticipated after a good clover-crop is 

 generally admitted ; the power of the clover to accumulate nitro- 

 genous matter in the soil, which explains this result, may not be 

 as fully recognised. Moreover, whilst few soils contain more 

 than traces of phosphoric acid, nearly every kind of agricultural 

 produce contains this acid in very large and often preponderating 

 proportions ; its presence being further required to furnish the 

 phosphorus which largely enters into the composition of albu- 



