The next experiments we shall describe are those on the influence of farmyard manure on the wheat crop when grown continuously.
TABLE IV.—Wheat grown continuously with Farmyard Manure (14 tons per annum).
| Weight per | Straw | ||
| Bushels. | bushel (lb.) | (cwts.) | |
| 8 years (1844-1852) | 28 | — | — |
| 20 years (1852-1871) | 35-7/8 | 60 | 33-7/8 |
| 20 years (1872-1891) | 33-1/2 | 60-3/8 | 31-3/8 |
| 40 years (1852-1891) | 34-7/8 | 60-1/4 | 32-5/8 |
It will be seen from the above results, which contain merely a selection from a very much greater number of experiments, that farmyard manure gives as good an average over the forty years as most of the artificial mixtures do. That this is due to the nitrogen it contains, is strikingly illustrated by the fact that mixed mineral manures alone give less than half the return, and also by the fact that ammonia salts alone give a return twice as great as mineral mixtures; while, lastly, the mixture of mineral manures and ammonia salts gives but a slight increase over that obtained with ammonia salts alone.
The remaining results, selected from a much larger number, need no comment, and we shall give them in tabular form.
Table V.—Wheat grown continuously with Artificial Manures, Farmyard Manure, and Unmanured.
Average of Forty Years (1852-91).
| Produce per Acre—Average per Annum. | |||
| Dressed grain. | |||
| Manures per Acre per Annum. | Quantity. | ||
| 20 years, | 20 years, | 40 years, | |
| 1852-71. | 1872-91. | 1852-91. | |
| bush. | bush. | bush. | |
| Farmyard manure, 14 tons per annum since 1843 | 35-7/8 | 33-1/2 | 34-7/8 |
| Unmanured continuously | 14-1/2 | 11-1/2 | 13 |
| Mixed mineral manures1 and 3-1/2 cwt. superphosphate | 17 | 12-7/8 | 15 |
| Mixed mineral manures, 3-1/2 cwt. superphosphate, 200 lb. ammonium salts | 26-1/2 | 21-3/4 | 24-1/8 |
| Mixed mineral manures and 3-1/2 cwt. superphosphate, 600 lb. ammonium salts | 38-1/4 | 34-3/4 | 36-1/2 |
| Mixed mineral manures, 3-1/2 cwt. superphosphate, 275 lb. nitrate of soda | 36-7/8 | 34 | 35-3/8 |
| 275 lb. nitrate of soda | 26 | 19-3/8 | 22-3/4 |
| 400 lb. ammonium salts every year since 1845 | 22-1/2 | 19 | 22-1/2 |
| 400 lb. ammonium salts, 3-1/2 cwt. superphosphate | 28 | 22-1/4 | 25-1/8 |
| Mineral manure, 3-1/2 cwt. superphosphate, 400 lb. ammonium salts in autumn. | 31-5/8 | 29-1/2 | 30-1/2 |
| 1By the term mixed mineral manures is meant a mixture of mineral fertilisers, not including phosphates. | |||
TABLE V.—continued
| Produce per Acre—Average per Annum. | |||
| Dressed grain. | |||
| Manures per Acre per Annum. | Weight per bushel. | ||
| 20 years, | 20 years, | 40 years, | |
| 1852-71. | 1872-91. | 1852-91. | |
| lb. | lb. | lb. | |
| Farmyard manure, 14 tons per annum since 1843 | 60 | 60-3/8 | 60-1/4 |
| Unmanured continuously | 57-5/8 | 58-3/4 | 58-1/4 |
| Mixed mineral manures and 3-1/2 cwt. superphosphate | 58-7/8 | 59 | 58-7/8 |
| Mixed mineral manures, 3-1/2 cwt. superphosphate, 200 lb. ammonium salts | 59-3/8 | 60 | 59-5/8 |
| Mixed mineral manures and 3-1/2 cwt. superphosphate, 600 lb. ammonium salts | 59 | 60 | 59-1/2 |
| Mixed mineral manures, 3-1/2 cwt. superphosphate, 275 lb. nitrate of soda | 58-3/8 | 59-5/8 | 59 |
| 275 lb. nitrate of soda | 56-5/8 | 56-5/8 | 56-5/8 |
| 400 lb. ammonium salts every year since 1845 | 58 | 57-3/8 | 57-5/8 |
| 400 lb. ammonium salts, 3-1/2 cwt. superphosphate | 57-3/8 | 58 | 57-5/8 |
| Mineral manure, 3-1/2 cwt. superphosphate, 400 lb. ammonium salts in autumn | 59-1/2 | 60 | 59-3/4 |