In 1870 the above experiments were repeated on the same land, with the same general results.
In 1871 some experiments were made on a sharp, gravelly soil, which had been over-cropped, and was in poor condition. The following are the results:—
| Bushels per acre. | ||
|---|---|---|
| 1. | 9 cwt. superphosphate | 186 |
| 3 cwt. sulphate of ammonia | ||
| 2. | 9 cwt. superphosphate | 204 |
| 3½ cwt. muriate of potash | ||
| 3 cwt. sulphate of ammonia | ||
| 3. | No manure | 70 |
| 4. | 9 cwt. superphosphate | 205 |
| 3½ cwt. muriate of potash | ||
| 3 cwt. sulphate of ammonia | ||
| 5. | 20 tons farm-yard manure | 197 |
“On this poor soil,” said the Doctor, “the ammonia and superphosphate gave an increase of 116 bushels per acre; and 3½ hundred weight of muriate of potash an increase, on one plot, of eighteen bushels, and on the other nineteen bushels per acre.”
In the same year, 1871, another set of experiments was made on a better and more loamy soil, which had been in grass for several years. In 1869 it was sown for hay, and in 1870 was broken up and sown to oats, and the next spring planted with potatoes. The following are some of the results:
| Bushels per acre. | ||
|---|---|---|
| 1. | 6¼ cwt. superphosphate | 321 |
| 2½ cwt. muriate of potash | ||
| 2½ cwt. sulphate of ammonia | ||
| 2. | 6¼ cwt. superphosphate | 296 |
| 2½ cwt. sulphate of ammonia | ||
| 3. | No manure | 252 |
| 4. | 6¼ cwt. superphosphate | 311 |
| 2½ cwt. muriate of potash | ||
| 5. | 2½ cwt. sulphate of ammonia | 238 |
| 6. | 15 tons farm-yard manure | 365 |
“It is curious,” said the Doctor, “that the plot with sulphate of ammonia alone should produce less than the no-manure plot.”
“The sulphate of ammonia,” said I, “may have injured the seed, or it may have produced too luxuriant a growth of vine.”
Another series of experiments was made on another portion of the same field in 1871. The “no-manure” plot produced 337 bushels per acre. Manures of various kinds were used, but the largest yield, 351 bushels per acre, was from superphosphate and sulphate of ammonia; fourteen tons barn-yard manure produce 340 bushels per acre; and Mr. Hunter remarks: “It is evident that, when the produce of the unmanured soil reaches nine tons [336 bushels] per acre, there is but little scope for manure of any kind.”