| Soil dried at 212 deg. Fahr. | |||
| 1st six inches. | 2d six inches. | 3d six inches. | |
|---|---|---|---|
| Percentage of phosphoric acid | .249 | .134 | .172 |
| Nitrogen | 1.62 | .092 | .064 |
| Equal to ammonia | .198 | .112 | .078 |
“In the upper six inches, as will be seen, the percentage of both phosphoric acid and nitrogen, was larger than in the two following layers, while the proportion of nitrogen in the six inches of surface soil, was much larger than in the next six inches; and in the third section, containing no visible particles of root-fibres, only very little nitrogen occurred.
“In their natural state, the three layers of soil contained:
| 1st six inches. | 2d six inches. | 3d six inches. | |
|---|---|---|---|
| Moisture | 17.16 | 18.24 | 16.62 |
| Phosphoric acid | .198 | .109 | .143 |
| Nitrogen | .134 | .075 | .053 |
| Equal to ammonia | .162 | .091 | .064 |
| lbs. | lbs. | lbs. | |
| Weight of one foot square of soil | 60 | 61 | 63 |
“Calculated per acre, the absolute weight of one acre of this land, six inches deep, weighs:
| Lbs. | |
|---|---|
| 1st six inches | 2,613,600 |
| 2d six inches | 2,657,160 |
| 3d six inches | 2,746,280 |
“No great error, therefore, will be made, if we assume in the subsequent calculations, that six inches of this soil weighs two and one-half millions of pounds per acre.
“An acre of land, according to the preceding determinations, contains:
| 1st six inches, Lbs. | 2d six inches, Lbs. | 3d six inches, Lbs. | |
|---|---|---|---|
| Phosphoric acid | 4,950 | 2,725 | 3,575 |
| Nitrogen | 3,350 | 1,875 | 1,325 |
| Equal to ammonia | 4,050 | 2,275 | 1,600 |
“The proportion of phosphoric acid in six inches of surface soil, it will be seen, amounted to about two-tenths per cent; a proportion of the whole soil, so small that it may appear insufficient for the production of a good corn-crop. However, when calculated to the acre, we find that six inches of surface soil in an acre of land, actually contain over two tons of phosphoric acid. An average crop of wheat, assumed to be 25 bushels of grain, at 60 lbs. per bushel, and 3,000 lbs. of straw, removes from the land on which it is grown, 20 lbs. of phosphoric acid. The clover-soil analyzed by me, consequently contains an amount of phosphoric acid in a depth of only six inches, which is equal to that present in 247½ average crops of wheat; or supposing that, by good cultivation and in favorable seasons, the average yield of wheat could be doubled, and 50 bushels of grain, at 60 lbs. a bushel, and 6,000 lbs. of straw could be raised, 124 of such heavy wheat-crops would contain no more phosphoric acid than actually occurred in six inches of this clover-soil per acre.