EXPERIMENTS WITH DIFFERENT TOP- 

 DRESSINGS UPON WHEAT. 



THERE is no lack of experiments made with guano, nitrate of 

 soda, soot, shoddy, gas-water, and other nitrogenized substances, 

 which are occasionally used as top-dressings upon wheat. Ex- 

 perience has shown that all these manures may be used, with 

 more or less advantage, for the wheat-crop ; and that, generally 

 speaking, they are the more effective the more nitrogen they 

 contain. Thus Peruvian guano or nitrate of soda, which are both 

 very rich in nitrogen, are justly considered more powerful wheat- 

 manures than soot or shoddy two materials much poorer in this 

 element. Whilst I consider the relative proportions of nitrogen 

 in different fertilizers, intended to be used for wheat or other 

 cereal crops, to be an important element in estimating the com- 

 parative commercial and agricultural value of artificial manures, 

 such as Peruvian guano, nitrate of soda, or sulphate of ammonia, 

 I am of opinion that the form or state of combination in which 

 the nitrogen is contained in the manure materially affects its 

 efficacy. Any one who has tried side by side nitrate of soda, 

 Peruvian guano, and shoddy, must have felt surprised at the 

 different degree of rapidity with which the effects of these three 

 fertilizers are rendered perceptible in the field. I have noticed 

 more than once that, under favourable circumstances, the effects 

 of nitrate of soda became visible in the course of three or four 

 days in the darker green colour and more luxuriant appearance 

 of the young wheat, whilst it took eight or ten days in the case 

 of guano to produce a similar effect. On wheat dressed with 

 shoddy no apparent effect was produced even after the lapse 01 

 four or six weeks. So slow is the action of the latter that a 

 superficial observer might well doubt the efficacy of shoddy as a 

 wheat-manure, for it often produces no visible improvement in 

 the wheat-crop, and it is only after threshing out the corn that it 

 can be ascertained that shoddy has had some effect upon the 

 yield of corn. These examples appear to indicate that nitrogen 

 in the shape of nitric acid has a different practical value from 

 that which it possesses in the shape of ammonia, and that it has 

 again another value in the form of nitrogenized organic matter. 

 It must be confessed that our knowledge of the comparative 

 efficacy of nitrogen, in its various states of combination, is 

 extremely limited, inasmuch as we scarcely possess any suffi- 

 ciently accurate and trustworthy comparative field experiments 

 which are calculated to throw light on this subject. As yet the 

 sure foundation on which an explicit opinion as to the relative 

 merits of nitrogen in the shape of nitric acid, ammonia, or or- 



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