Three Years of Barley after Ten Years of Turnips.
| PARTICULARS OF MANURES,ETC. | Produce of Barley per Acre. | |||
|---|---|---|---|---|
| 1853. | 1854. | 1855. | Average 3 years | |
| bush. | bush. | bush. | bush. | |
Hoos-Field— | 26 | 35⅛ | 34⅛ | 31⅜ |
Barn-Field— | ||||
1.—Mineral manures (last 8 years) | 20½ | 19½ | 20 | 20 |
2.—Mineral manures (8 yrs.); Ammonia-salts (6 yrs.). | 23⅛ | 21¼ | 21¾ | 22 |
3.—Mineral manures (8 yrs.); Rape-cake (6 yrs.) | 28¾ | 24⅝ | 23⅛ | 25¾ |
4.—Mineral manures (8 yrs.); Ammonia-salts and Rape-cake(6 yrs.) | 29⅛ | 23¾ | 23¾ | 25⅝ |
5.—Mineral manures (8 yrs.); Ammonia-salts, for Barley,1854 | (20½) | 52⅜ | 26⅝ | 39½ |
6.—Mineral manures (8 yrs.); Ammonia-salts, for Barley, ’54 and’55 | (20½) | 54⅞ | 49⅜ | 47⅝ |
The yield of barley after turnips is less than it is after grain crops, and it is evident that this is due to a lack of available nitrogen in the soil. In other words, the turnips leave less available nitrogen in the soil than grain crops.
After alluding to the facts given in the foregoing table, Messrs. Lawes and Gilbert say:
“There is evidence of another kind that may be cited as showing that it was of available nitrogen that the turnips had rendered the soil so deficient for the after-growth of barley. It may be assumed that, on the average, between 25 and 30 lbs. of nitrogen would be annually removed from the Rothamsted soil by wheat or barley grown year after year without nitrogenous manure. But it is estimated that from the mineral-manured turnip-plots there were, over the 10 years, more than 50 lbs. of nitrogen per acre per annum removed. As, however, on some of the plots, small quantities of ammonia-salts or rape-cake were applied in the first two years of the ten of turnips, it is, perhaps, more to the purpose to take the average over the last 8 years of turnips only; and this would show about 45 lbs. of nitrogen removed per acre per annum. An immaterial proportion of this might be due to the small amounts of nitrogenous manures applied in the first two years. Still, it may be assumed that about 1½ time as much nitrogen was removed from the land for 8, if not for 10 years, in succession, as would have been taken in an equal number of crops of wheat or barley grown without nitrogenous manure. No wonder, then, that considerably less barley has been grown in 3 years after a series of mineral-manured turnip-crops, than was obtained in another field after a less number of corn-crops.
“The results obtained in Barn-field afford a striking illustration of the dependence of the turnip-plant on a supply of available nitrogen within the soil, and of its comparatively great power of exhausting it. They are also perfectly consistent with those in Hoos-field, in showing that mineral manures will not yield fair crops of barley, unless there be, within the soil, a liberal supply of available nitrogen. The results obtained under such very different conditions in the two fields are, in fact, strikingly mutually confirmatory.”