| Percentage of | ||
| 1857. | Nitrate of Potash. | = lb. per acre. |
| August 5 | .01 | 34 |
| August 17 | .06 | 222 |
| September 2 | .18 | 634 |
| September 17 | .22 | 760 |
| October 2 | .21 | 728 |
NOTE VII. (p. 188).
Nitrogen as Nitrates in Rothamsted Soils after bare fallow in Lb. per Acre.
| Alternate | Four-course rotation. | |||||
| Wheat | Super- | |||||
| Depth of | and | phosphate | Claycroft | Foster's | ||
| Soil. | Fallow. | only. | Mixed Manure. | Field. | Field. | |
| 1878. | 1878. | 1878. | 1882. | 1881. | 1881. | |
| lb. | lb. | lb. | lb. | lb. | lb. | |
| 1st 9 ins. | 28.5 | 22.3 | 30.0 | 40.1 | 16.4 | 14.6 |
| 2d 9 ins. | 5.2 | 14.0 | 18.8 | 14.3 | 26.5 | 24.6 |
| 3d 9 ins. | — | — | — | 5.5 | 15.9 | 17.3 |
| Total | 33.7 | 36.3 | 48.8 | 59.9 | 58.8 | 56.5 |
CHAPTER V.
THE POSITION OF PHOSPHORIC ACID.
We now come to consider the position of phosphoric acid in agriculture. The question is, however, very much simpler in its nature than that of nitrogen, and may be consequently discussed in a much shorter space.
Most soils, as we have already had occasion to point out, are better supplied with available ash-plant ingredients than available nitrogen compounds. The quantity of phosphoric acid absorbed by the plant is also less than that of nitrogen; and lastly, the different chemical compounds of phosphoric acid occurring in the soil are not nearly so numerous as those of nitrogen. Phosphoric acid, however, must be regarded as ranking next to nitrogen in its importance as a soil-constituent.