| Lbs. | |
|---|---|
| Surface, six inches … … … | 2,407,900 |
| Next six inches … … … | 2,444,200 |
| Third six inches … … … | 2,480,500 |
“Or in round numbers, every six inches of soil weighed per acre 2½ millions of pounds, which agrees tolerably well with the actual weight per acre of the preceding soil.
“The amount of phosphoric acid and nitrogen in each six-inch layer was determined separately, as before, when the following results were obtained:
| First six inches. | Second six inches. | Third six inches. | |
|---|---|---|---|
| Percentage of phosphoric acid | .159 | .166 | .140 |
| Nitrogen | .189 | .134 | .089 |
| Equal to ammonia | .229 | .162 | .108 |
“An acre, according to these determinations, contains in the three separate sections:
| First six inches. lbs. | Second six inches. lbs. | Third six inches. lbs. | |
|---|---|---|---|
| Phosphoric acid | 3,975 | 4,150 | 3,500 |
| Nitrogen | 4,725 | 3,350 | 2,225 |
| Equal to ammonia | 5,725 | 4,050 | 2,700 |
“Here, again, as might naturally be expected, the proportion of nitrogen is largest in the surface, where all the decaying leaves dropped during the growth of the clover for seed are found, and wherein root-fibres are more abundant than in the lower strata. The first six inches of soil, it will be seen, contained in round numbers, 2½ tons of nitrogen per acre, that is, considerably more than was found in the same section of the soil where the clover was mown twice for hay; showing plainly, that during the ripening of the clover seed, the surface is much enriched by the nitrogenous matter in the dropping leaves of the clover-plant.
“Clover-roots.—The roots from one square foot of this soil, freed as much as possible from adhering soil, were dried at 212°, and when weighed and reduced to a fine powder, gave, on analysis, the following results:
| Organic matter* | 64.76 |
| Mineral matter† | 35.24 |
| 100.00 | |
| * Containing nitrogen | 1.702 |
| Equal to ammonia | 2.066 |
| † Including clay and sand (insoluble silicious matter) | 26.04 |