SOURCES OF AMMONIA. 97 



any farm-lot, whatever be the crop, which a good dressing of 

 bones or mineral phosphates will not benefit. The task, then, 

 to demonstrate that these manures (phosphates and alkalies) 

 are not highly beneficial to the land will hardly be undertaken. 



Ammonia, the source of nitrogen to the plant, occupies, how- 

 ever, a different position with reference to the farmer. There 

 is an abundance in the air for all natural vegetation. It exists 

 in the humus which forms in, and, we may say, is essential to, 

 all tillable soils, and by the air and the humus is easily given 

 up to the plant. So far as vegetation is concerned, it is as uni- 

 versally diffused as water. 



There is some ground, then, for philosophers to argue against 

 placing a very high value upon this widely disseminated sub- 

 stance. 



When, however, we come to the direct testimony of the soil 

 and the farmers, we find its application productive, upon tolera- 

 bly good soils, of fairly startling results. 



If all the essential ash constituents abound in the soil, in 

 connection with good tillage and proper mechanical conditions, 

 with no lack of water, even though no ammonia be present, 

 save that which is in the air, there will be good crops of grain, 

 but the addition of ammonia produces those wonderful crops 

 which otherwise only virgin soils of great richness ever yield. 



Without, then, entering upon the consideration of what 

 classes of crops are most benefited by ammonia, and which 

 respond most noticeably to applications of the phosphates, it is 

 enough for our present purpose to recognize this distinction, 

 viz. : that the highest effects of phosphate of lime, in any form, 

 and of wood-ashes, the source of potash, are seen on rather 

 hard, worn, but naturally good soils ; while the best effects of 

 ammoniacal manures are observed in connection with these 

 inorganic constituents, existing in the soil in sufficient abun- 

 dance, or applied with the ammoniacal manure. We use the 

 terms ammoniacal and nitrogenous as nearly synonymous. The 

 distinction should always be recognized between manures which 

 yield quickly to the influences of decomposition, and those in 

 which the nitrogen is so locked up that it remains long in the 

 soil. Thus, leather clippings yield much ammonia, but they are 

 a very long time in undergoing decomposition. Fresh ground 

 bones yield to the plant both phosphoric acid and ammonia, but 

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