“A field of 11 acres was sown to winter-wheat, and seeded down in the spring, with 13 lbs. per acre of clover. The wheat yielded 40 bushels per acre. The next year, on the 25th of June, the clover was mown for hay. We are told that ‘the best part of the field yielded three tons (6,720 lbs.) of clover-hay per acre; the whole field averaging 2½ tons (5,600 lbs.) per acre.’
“We are not informed how much land there was of the ‘best part,’ but assuming that it was half the field, the poorer part must have yielded only 4,480 lbs. of hay per acre, or only two-thirds as much as the other. This shows that there was considerable difference in the quality or condition of the land.
“After the field was mown for hay, it was divided into two parts: one part was mown again for hay, August 21st, and yielded about 30 cwt. (3,360 lbs.) of hay per acre; the other half was allowed to grow six or seven weeks longer, and was then (October 8th), cut for seed. The yield was a little over 5½ bushels of seed per acre. Whether the clover allowed to grow for seed, was on the richer or poorer half of the field, we are not informed.
“Dr. Vœlcker then analyzed the soil. That from the part of the field mown twice for hay, contained per acre:
| First six inches. | Second six inches. | Third six inches. | Total, 18 inches deep. | |
|---|---|---|---|---|
| Phosphoric acid | 4,950 | 2,725 | 3,575 | 11,250 |
| Nitrogen | 3,350 | 1,875 | 1,325 | 6,550 |
“The soil from the part mown once for hay, and then for seed, contained per acre:
| First six inches. | Second six inches. | Third six inches. | Total, 18 inches deep. | |
|---|---|---|---|---|
| Phosphoric acid | 3,975 | 4,150 | 3,500 | 11,625 |
| Nitrogen | 4,725 | 3,350 | 2,225 | 10,300 |
“Dr. Vœlcker also ascertained the amount and composition of the clover-roots growing in the soil on the two parts of the field. On the part mown twice for hay, the roots contained per acre 24½ lbs. of nitrogen. On the part mown once for hay, and then for seed, the roots contained 51½ lbs. of nitrogen per acre.”
“Now,” said the Doctor, “these facts are very interesting, but there is no sort of evidence tending to show that the clover has anything to do with increasing or decreasing the quantity of nitrogen or phosphoric acid found in the soil.”
“There was more clover-roots per acre, where the clover was allowed to go to seed. But that may be because the soil happened to be richer on this part of the field. There was, in the first six inches of the soil, 3,350 lbs. of nitrogen per acre, on one-half of the field, and 4,725 lbs. on the other half; and it is not at all surprising that on the latter half there should be a greater growth of clover and clover-roots. To suppose that during the six or seven weeks while the clover was maturing its seed, the clover-plants could accumulate 1,375 lbs. of nitrogen, is absurd.”