“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.” “But Dr. Vœlcker,” said the Deacon, “states, and states truly, that ‘more leaves fall on the ground when clover is grown for seed, than when it is mown for hay; and, consequently, more nitrogen is left after clover-seed than after hay, which accounts for wheat yielding a better crop after clover-seed than after hay.’” “This is all true,” said the Doctor, “but we can not accept Dr. Vœlcker’s analyses as proving it. To account in this way for the 1,375 lbs. of nitrogen, we should have to suppose that the clover-plants, in going to seed, shed _one hundred tons_ of dry clover-leaves per acre! The truth of the matter seems to be, that the part of the field on which the clover was allowed to go to seed, was naturally much richer than the other part, and consequently produced a greater growth of clover and clover-roots.” We can not find anything in these experiments tending to show that we can make land rich by growing clover and selling the crop. The analyses of the soil show that in the first eighteen inches of the surface-soil, there was 6,550 lbs. of nitrogen per acre, on one part of the field, and 10,300 lbs. on the other part. The clover did not create this nitrogen, or bring it from the atmosphere. The wheat with which the clover was seeded down, yielded 40 bushels per acre. If the field had been sown to wheat again, it probably would not have yielded over 25 bushels per acre--and that for want of available nitrogen. And yet the clover got nitrogen enough for over four tons of clover-hay; or as much nitrogen as a crop of wheat of 125 bushels per acre, and 7½ tons of straw would remove from the land. Now what does this prove? There was, in 18 inches of the soil on the poorest part of the field, 6,550 lbs. of nitrogen per acre. A crop of wheat of 50 bushels per acre, and twice that weight of straw, would require about 92 lbs. of nitrogen. But the wheat can not get this amount from the soil, while the clover can get _double the quantity_. And the only explanation I can give, is, that the clover-roots can take up nitrogen from a weaker solution in the soil than wheat-roots can.