KEY: A: Dressed Corn, bushels. B: Straw and Chaff, cwts. C: Total Produce, lbs. D: Corn to 100 Straw. E: Weight per Bushel of Dressed Corn, lbs. F: Produce of second 10 yrs. over or under first 10 yrs, per cwt.
| Manures per Acre. | A | B | C | D | E | F |
| Unmanured. | 20 | 113⁄4 | 2454 | 86·6 | 52·3 | -23·6 |
| Mixed cinerials. | 271⁄2 | 143⁄8 | 3162 | 96·4 | 53·4 | -20·2 |
| Ammonium salts, 200 lbs. | 321⁄2 | 181⁄2 | 3919 | 89·2 | 52·1 | -9·7 |
| Ammonium salts, 200 lbs., and alkali salts. | 35 | 203⁄4 | 4317 | 86·3 | 52·8 | -5·3 |
| Ammonium salts, 200 lbs., and superphosphate. | 47 | 275⁄8 | 5760 | 86·8 | 53·5 | +2·7 |
| Ammonium salts, 200 lbs., and cinerials. | 461⁄4 | 281⁄2 | 5817 | 83·2 | 54·0 | -·3 |
| Rape cake (mean 1300 lbs.) | 451⁄4 | 267⁄8 | 5571 | 87·3 | 53·8 | |
| Farmyard manure, 14 tons. | 481⁄4 | 281⁄4 | 5933 | 88·5 | 54·3 | +14·8 |
The authors direct attention to the results obtained by using the cinerial manure alone, as illustrating the unsoundness of the old “mineral theory,” according to which plants were supposed to possess a sufficient source of nitrogen in the atmosphere. They found a greater crop yielded by barley than wheat, when no manures were employed, as well as when cinerials were employed, a fact which they attribute to barley being better able than wheat to supply itself with nitrogen, notwithstanding the deeper roots of the latter. They state that with both wheat and barley the produce is slowly falling off under these circumstances. With ammonium salts alone, and with nitrate of sodium alone, there is much less falling off than when no nitrogenous manure is used. The falling off was least with the nitrate. The nitrate gives a rather larger crop for the same amount of nitrogen supplied, and they found this to hold when both nitrate and ammonia are applied with cinerials. The addition of superphosphate to ammonium salts or sodium nitrate greatly increases the produce; the further addition of potassium, sodium, and magnesium salts they found almost without effect.
The inference was that the barley had obtained an ample supply of potash from the natural soil, but an insufficient supply of phosphoric acid.
When ammonium salts are used alone, and the quantity of ammonia does not exceed 50 lbs. per acre, 3·68 lbs. of ammonia will yield an average increase of 1 bushel of corn and 63 lbs. of straw—total, 115 lbs.; the extremes in 20 years were 2·25-18·05 lbs. When ammonium salts are applied with superphosphate, 2·21 lbs. of ammonia will produce the same result; the extremes were 1·47-5·36 lbs.
Silicate of sodium had been applied for eight years and a half to half the barley plots receiving ammonia; no increase has resulted where ammonia and superphosphate are employed; but on the other three plots an increase had taken place, which, in the case of the plot receiving only ammonia and alkali salts, is very considerable.
The authors think this irregular reaction seems to show that the silicate has not produced its effect by furnishing silica to the crop, but by some reaction upon the plant-food of the soil. The rape cake supplied much more nitrogen than the ammonium salts, and also some phosphates and potash. Rape cake alone gives a better return than either ammonium salts or sodium nitrate applied alone; but when the three manures are mixed with superphosphate, the results for equal amounts of nitrogen show the rape cake to be decidedly inferior. From the above experiments it is inferred that a supply of carbonaceous matter does not increase the crop of barley.
A farm-yard manure containing about 0·64 per cent. of nitrogen supplied far more plant food than any of the other manures. On an
average of twenty years it was found that about 8 lbs. of ammonia in the form of dung would produce a bushel of barley, with its equivalent of straw.
In all cases which were comparable it was found that barley appropriates more of the nitrogenous manure than wheat, save with farmyard manure. A large amount of nitrogen applied by manure is not taken up by the crop. Experiments in the barley field proved that large residues from ammonium salts and sodium nitrate show a small but distinct effect upon succeeding crops, the influence extending over many years. From an examination of the drainage waters from lands dressed with the nitrates of ammonium and sodium, the authors conclude that ammonium salts, as well as sodium nitrate, will be more economically applied in the spring than in the winter. Manures containing organic nitrogen are clearly not so liable to loss from drainage.