Pliuspltdtic JMaterials nscfl for Af/riviiUnral Purposes. ool 
and not been found to realize the expectations raised, superplios- 
pliatc and similar pliospliatic manures have maintained a firm 
hold in the good opinion of the agriculturist. Far be it from 
mo 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 all)u- 
