222 IS NITRIC ACID FOOD FOR PLANTS ? 



exactly opposed to ammonia ; but we see, that in the organism 

 of plants, carbonic acid and water suffer decomposition, although 

 their constituents are united by a much greater power. We 

 have considered sulphuric acid as a source of sulphur. Why, 

 then, should not nitric acid suffer a similar decomposition by the 

 same causes ; why should not its nitrogen, like the carbon or 

 sulphur, become a component part of a plant ? 



By strewing nitrate of soda over fields, a greater crop has been 

 obtained, particularly on grass land. Upon corn-fields and on 

 roots, it has had less influence. 



It is not yet decided to what constituent of the salt its favorable 

 influence is due. 



When the crops of hay and straw obtained with this manure 

 by Mr. Gray, of Dilston, and Mr. Hyett (Journal of the Royal 

 Agricultural Society), are expressed with regard to their quantity 

 of nitrogen, the singular result is obtained, that the amount of 

 nitrogen in these crops amounts to double the quantity of that 

 contained in the nitrate used as manure ! 



Now, when it is remembered that the crop of many meadows 

 is rendered a half, twice, or even three times greater, by ma- 

 nuring with burnt bones or with wood ashes — with matters, 

 therefore, containing no nitrogen, it still remains doubtful 

 whether the action of nitrate of soda should be ascribed to its 

 nitric acid. 



A number of plants, such as Borago officinalis, Mesembryan- 

 themum crystallinum, Ajpium graveolens, the sun-flower, and to- 

 bacco, contain dissolved in their juices considerable quantities of 

 nitre, which does not exist in other plants growing on the same 

 soil. The presence of a nitrate in plants permits only one con- 

 clusion — that the nitrogen of nitric acid is not employed in their 

 organism for the formation of compounds containing that element, 

 because, if it were, at a certain period of the life of the plant, it 

 would disappear on account of this conversion. 



Whatever be the case in this respect, nitrates are manures, 

 which do not replace those constituents of the soil which are re- 

 moved in the crops. Hence, although cither by means of their 

 fccid, or of their alkalies, the rowth of plants may be increased 

 for one or two years, this very increase must cause an earlier 



