The twelfth season (1854-5), gives us 17 bushels of wheat per acre on the continuously unmanured plot. Over 34½ bushels on the plot manured with barn-yard manure. And I think, for the first time since the commencement of the experiments, this plot produces the largest yield of any plot in the field. And well it may, for it has 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 14½ bushels on the unmanured plot; over 36¼ bushels on the plot manured with barn-yard manure; and over 40 bushels on 8a, dressed with 600 lbs. ammonia-salts and mixed mineral manures. It will be noticed that 800 lbs. ammonia-salts does not give quite as large a yield this year as 600 lbs. I suppose 40 bushels per acre was all that the season was capable of producing, and an extra quantity of ammonia did no good. 400 lbs. of ammonia-salts, on 7a, produced 37¼ bushels per acre, and 800 lbs. on 16b, only 37¾ 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 5a gives nearly 23 bushels per acre. Mixed mineral manures and 200 lbs. ammonia-salts, on 6a, give 35¼ bushels. In other words the ammonia gives us over 12 extra bushels of wheat, and 1,140 lbs. of straw. Mineral manures and 400 lbs. ammonia-salts, on 7b, give 46¼ bushels per acre. Mineral manures and 600 lbs. ammonia-salts, on 8b, give nearly 49 bushels per acre. Mineral manures and 800 lbs. of ammonia-salts, on 16b, give 50 bushels per acre, and 4,703 lbs. of straw.
“This exceedingly heavy manuring,” said the Deacon, “does not pay. For instance,
| “200 lbs. ammonia-salts give an increase of | 12¼ bushels per acre. |
| 400 ”””” | 23¼ ”” |
| 600 ”””” | 26 ”” |
| 800 ”””” | 27 ”” |
The Deacon is right, and Mr. Lawes and Dr. Gilbert call especial attention to this point. The 200 lbs. of ammonia-salts contain about 50 lbs. of ammonia, and the 400 lbs., 100 lbs. of ammonia. And as I have said, 100 lbs. of ammonia per acre is an unusually heavy dressing. It is as much ammonia as is contained in 1,000 lbs. 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 barnyard manure. Mixed mineral manures on 5a and 5b, give a mean yield of less than 19 bushels per acre.
Mixed mineral manures and 100 lbs. ammonia-salts, on plots 21 and 22, give 23¼ bushels per acre. In other words:
| 25 lbs. ammonia (100 lbs. ammonia-salts), | gives an increase of 4¼ bush. |
| 50 lbs. ammonia (200 lbs. ammonia-salts), | gives an increase of 10 bush. |
| 100 lbs. ammonia (400 lbs. ammonia-salts), | gives an increase of 20 bush. |
| 150 lbs. ammonia (600 lbs. ammonia-salts), | gives an increase of 23 bush. |
| 200 lbs. ammonia (800 lbs. ammonia-salts), | gives an increase of 23 bush. |