SENSIBLE EFFECTS OF THE NITRATES. 173 



2. Sensible effects produced by the application of the nitrates 

 of potash and soda. 



These nitrates, when applied to growing crops, produce cer- 

 tain sensible effects, which I enumerate separately 



1. They give a beautiful dark green and luxuriant appear- 

 ance to the leaf. This they do in common with substances con- 

 taining ammonia, and hence it is usually ascribed to the influence 

 of the nitrogen which ammonia and nitric acid contain in common. 

 This opinion is supported by the fact that the sulphates and 

 other salts of potash and soda do not produce such a darken- 

 ing or freshening effect upon the green of the leaf. 



2. They increase the rapidity of growth, the succulence, and 

 the apparent bulk. In the case of grass they do not always add 

 to the weight of the crops when dried into hay, the greater bulk 

 sometimes deceiving the eye and disappointing the hopes of the 

 farmer. It is a question, however, whether this greater succu- 

 lence, supposing the weight of the crop to be the same, is not in 

 itself a positive money benefit in the feeding of cattle. Such 

 bulky, succulent food ought, when eaten green, to dissolve more 

 completely in the stomach, and thus to yield more nourishment 

 than such as is harder, denser, and of slower growth. It may 

 even be so also with the hay made from the two portions of 

 green grass. The more succulent may swell more in the digestive 

 canal, and, like the green grass, go farther. An inquiry into these 

 opinions offers a wide field of experiment to the practical feeder. 



3. They usually increase the quantity or produce of corn 

 crops, both grain and straw, but impair the quality or market 

 value per bushel. This is said to be especially the case in regard 

 to wheat. The increase in the actual weight of the crops to 

 which they are applied is not, however, invariable. 



4. Like common salt, they render the herbage to which they 

 are applied more agreeable to cattle ; so that those parts of a 

 field are eaten especially bare to which the nitrates have been 

 previously applied. 



It is truly wonderful to see all these effects produced by such 

 minute additions to the land. One hundredweight of nitrate 

 of soda per acre is only 20 grains to the square foot of land. 





