AMERICAN WHEAT AND CORN. 91 



variation is especially marked in the case of the potash and phosphoric 

 acid, and it is obviously much dependent on their supply. It is also 

 very marked in the case of the silica. 



11. Calculated per acre, there is very great variation in the amounts of 

 produce, and of its various constituents, according to manure. Without 

 manure and with purely mineral manure, the produce was very small; 

 it was much more with ammonium-salts alone, and much more still with 

 ammonium-salts and mineral manure together. With ammonium-salts 

 and the most complete mineral manure, there was more than one and a 

 half times as much produce as with ammoninin-salts alone, and nearly 

 two and and a half times as much as with mineral manure alone. There 

 were in the main corresponding differences in the amounts of nitrogen, 

 total mineral matter, and the chief individual ash constituent, stored 

 up in the crops. 



12. Of potash, the ashes show three times as much in the total pro- 

 duce per acre with farm-yard manure and more than three times as much 

 in that with ammonium-salts and mineral manure containing potash, as 

 without manure. On the other plots (excepting with mineral manure 

 alone), the quantities of potash in the crops are obviously dependent on 

 the supply. Of the total potash of the crops, there is generally only from 

 one-fourth to one-third accumulated in the grain. 



13. Of phosphoric acid there was little more than twice as much per 

 acre in the highly manured as in the unmanured produce; but three- 

 fourths or more of the total phosphoric acid of the crops may be accu- 

 mulated in the grain. 



14. Of the total lime and sulphuric acid of the crop a very small pro- 

 portion ; of the magnesia, generally more than half; of the chlorine, 

 scarcely a trace, and of the silica, the smallest proportion of all, is 

 found in the grain-ashes. 



15. With very great variation in the amounts of nitrogen and ash 

 constituents in the total crop per acre on the different plots, there is re- 

 markable uniformity in the amounts of each per 1,000 dry substance of 

 grain; but wide variation in the amounts per 1,000 dry substance of 

 straw. The greatest exceptions to uniformity in the amount of potash 

 per 1,000 dry substance of the grain are that it is low with ammonium- 

 salts alone, or with superphosphate only in addition (10 and lla), and 

 high without manure, and with purely mineral manure, (3 and 5a). 

 The most marked deviations from general uniformity in the amount of 

 phosphoric acid in the dry substance of the grain are, that it is low 

 with ammonium salts alone (10a), and high with farm-yard manure, 

 without manure, and with purely mineral manure (2, 3, and 5a). 



16. With every condition of manuring there is, in the grain ashes, a 

 liigher percentage of potash, and a lower of phosphoric acid, and some- 

 what lower of magnesia also, in the two favorable seasons, indicating 

 higher proportion of flour to bran. There is lower percentage of phos- 

 phoric acid in the better seasons, even where there is liberal supply of 



