EXPERIMENTS OX WHEAT. 211 



duces the largest yield of any plot in the field. And well it may, 

 for it lias now had, in twelve years, 168 tons of barn-yard manure 

 per acre ! 



Several of the plots with ammonia-salts and mixed minerals, 

 are nearly up to it in grain, and ahead of it in straw. 



The thirteenth season (1855-6), gives 14 bushels on the unmanur- 

 ed plot; over 3GJ bushels on the plot manured with barn-yard ma- 

 nure ; and over 40 bushels on S.'t, dressed with 600 Ibs. ammonia- 

 salts and mixed mineral manures. It will be noticed that 800 Ibs. 

 ammonia-salts does not give quite as large a yield this year as 600 

 Ibs. I suppose 40 bushels per acre was all that the season was capa- 

 ble of producing, and an extra quantity of ammonia did no good. 

 400 Ibs. of amjnonia-salts, on 7<z, produced 37| bushels per acre, 

 and 800 Ibs. on 166, only 37f bushels. That extra half bushel 

 of wheat was produced at considerable cost. 



The fourteenth season (1856-7), gives 20 bushels per acre on the 

 unmanured plot, and 41 bushels on the plot with barn-yard 

 manure. Mixed mineral manures alone on 5& gives nearly 23 

 bushels per acre. Mixed mineral manures and 200 Ibs. ammonia- 

 salts, on 6a, give 35 bushels. In other words the ammonia gives 

 us over 12 extra bushels of wheat, and 1,140 Ibs. of straw. 

 Mineral manures and 400 Ibs. ammonia-sails, on 75, give 46J 

 bushels per acre. Mineral manures and 600 Ibs. ammonia-salts, on 

 83, give nearly 49 bushels per acre. Mineral manures and 800 Ibs. 

 of ammonia-salts, on 165, give 50 bushels per acre, and 4,703 Ibs. 

 of straw. 



"This exceedingly heavy manuring," said the Deacon, "does 

 not pay. For instance, 



"200 Ibs. ammonia-salts give an increase of 12} bushels per acre. 

 400 " " " " 23* " " 



600 " " " " 26 " " 



800 " " " " 27 " u 



The Deacon is right, and Mr. Lawes and Dr. Gilbert call especial 

 a'tention to this point. The 200 Ibs. of ammonia-salts contain 

 about 50 Ibs. of ammonia, and the 400 IDS., 100 Ibs. of ammonia. 

 And as I have said, 100 Ibs. of ammonia per acre is an unusually 

 heavy dressing. It is as much ammonia as is contained in 1,000 

 Ibs. of average Peruvian guano. We will recur to this subject. 



The fifteenth season (1857-8,) gives a yield of 18 bushels of wheat 

 per acre on the continuously unmanured plot, and nearly 39 

 bushels on the plot continuously manured with 14 tons of barn- 

 yard manure. Mixed mineral manures on 5a and 55, give a mean, 

 yield of less than 19 bushels per acre. 



