On Guano. 



319 



of well -devised and carefully executed experiments in practical 

 agriculture* — not only to the general economy of the art of cul- 

 ture, but also to the establishment of a true theory of its various 

 processes — I shall take the liberty of introducing a few sugges- 

 tions in regard to the kind of experiments which appear to me 

 most likely to yield results at once economically and theoretically 

 useful. 



Among those substances which owe one main part of their 

 beneficial agency on vegetable life to the ammonia they contain or 

 evolve, may be reckoned farm-yard manure, crushed bones, and 

 rape- dust. As the nitrates also act upon plants in a way so far 

 similar to ammonia as to yield nitrogen to them, the nitrates of 

 potash and soda may be included in the list of substances with 

 which it would be desirable to compare the action of the guano. 

 The cost of all these substances is known, — they are all to a certain 

 extent in general use, — and w^hile comparative experiments accu- 

 rately made by weight and measure would throw light on many 

 obscure points in regard to the action of each of these manures, — 

 the results obtained from every separate plot of ground would serve 

 as so many points of comparison by means of which the absolute 

 and relative value of the guano might be determined. 



In the present state of our practical knowledge respecting this 

 substance, it will be pronounced by every one to be desirable that 

 its effect should be tried upon every kind of crop ; but the pro- 

 priety of this course is increased by our knowledge of its chemical 

 constitution. It contains the greater part of the ingredients which 

 are necessary to the growth of almost every variety of crop. It 

 will doubtless prove as efficacious therefore to old pasture-land as 

 to the rye-grass in Mr. Skirving's nursery, and to crops of corn as 

 to Mr. Pusey's turnips ; but experience alone can tell us to which 

 it may be applied with profit to the farmer, and from what crops it 

 will afford him the greatest return on a given soil. 



I would propose therefore that it should be tried during an 

 entire rotation to replace farm-yard manure and the other sub- 

 stances named, as well as against the mixture above described, 

 which I shall distinguish by the name of artificial guano. The 

 mode of making the experiments may be varied at the wish of 

 the practical farmer, but they might be made in a way similar to 

 that represented beneath, each square being a half or quarter acre 

 or other accurately m.easured plot of land. 



* See a small tract published by Blackwood, under the title of " Sug- 

 gestions FOR Experiments in Practical Agriculture." 



