“A square foot of this soil produced 582 grains of dried clover-roots, consequently an acre yielded 3,622 lbs. of roots, or more than twice the weight of roots obtained from the soil of the same field where the clover was twice mown for hay.
“In round numbers, the 3,622 lbs. of clover-roots from the land mown once, and afterwards left for seed, contained 51½ lbs. of nitrogen.
“The roots from the soil after clover-seed, it will be noticed, were not so clean as the preceding sample, nevertheless, they yielded more nitrogen. In 64.76 of organic matter, we have here 1.702 of nitrogen, whereas, in the case of the roots from the part of the field where the clover was twice mown for hay, we have in 81.33 parts, that is, much more organic matter, and 1.635, or rather less of nitrogen. It is evident, therefore, that the organic matter in the soil after clover-seed, occurs in a more advanced stage of decomposition, than found in the clover-roots from the part of the field twice mown. In the manure, in which the decay of such and similar organic remains proceeds, much of the non-nitrogenous, or carbonaceous matters, of which these remains chiefly, though not entirely, consist, is transformed into gaseous carbonic acid, and what remains behind, becomes richer in nitrogen and mineral matters. A parallel case, showing the dissipation of carbonaceous matter, and the increase in the percentage of nitrogen and mineral matter in what is left behind, is presented to us in fresh and rotten dung; in long or fresh dung, the percentage of organic matter, consisting chiefly of very imperfectly decomposed straw, being larger, and that of nitrogen and mineral matter smaller, than in well-rotted dung.
“The roots from the field after clover-seed, it will be borne in mind, were dug up in November, whilst those obtained from the land twice mown, were dug up in September; the former, therefore, may be expected to be in a more advanced state of decay than the latter, and richer in nitrogen.
“In an acre of soil, after clover-seed, we have:
| Lbs. | |
|---|---|
| Nitrogen in first six inches of soil | 4,725 |
| Nitrogen in roots | 51½ |
| Nitrogen in second six inches of soil | 3,350 |
| Total amount of nitrogen, per acre, in twelve inches of soil | 8,126½ |
“Equal to ammonia, 9,867 lbs.: or, in round numbers, 3 tons and 12½ cwts. of nitrogen per acre; equal to 4 tons 8 cwts. of ammonia.
“This is a very much larger amount of nitrogen than occurred in the other soil, and shows plainly that the total amount of nitrogen accumulates especially in the surface-soil, when clover is grown for seed; thus explaining intelligibly, as it appears to me, why wheat, as stated by many practical men, succeeds better on land where clover is grown for seed, than where it is mown for hay.
“All the three layers of the soil, after clover-seed, are richer in nitrogen than the same sections of the soil where the clover was twice mown, as will be seen by the following comparative statement of results:
| I. Clover-Soil twice mown. | II. Clover-Soil once mown and then left for seed. | |||||
| Upper 6 inches | Second 6 inches | Third 6 inches | Upper 6 inches | Next 6 inches | Lowest 6 inches | |
|---|---|---|---|---|---|---|
Percentage of nitrogen in dried soil | .168 | .092 | .064 | .189 | .134 | .089 |
| Equal to ammonia | .198 | .112 | .078 | .229 | .162 | .108 |