for Tioenty Years in succession on the same Land. 357 
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 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 atford a striking illustration 
of the dependence of the turnip-plant on a supply of avail- 
able 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. 
2. Barley in Four-Course Rotation of — Turnips, Barley, Clover 
or Beans, and Wlieat — Agdell-Field. 
These experiments, which are still in progress, were com- 
menced in 1848, so that the crop of 1871 was the twenty-fourth, 
and completed the sixth course. The produce of barley obtained 
in the first three courses was given in the paper above referred to, 
but it is now given, though in less detail for each course, for the 
six completed courses. 
The area of about 2 J acres was divided into three equal portions. 
One-third has been left entirely unmanured from the commence- 
ment ; one-thiid has been manured with superphosphate of 
lime * alone, once every 4 years, that is for the turnip-crop 
* Quantities per acre, as under — 
Bone-ash. 
Sulphuric Acid. 
(Sp, gr. 1-7). 
lbs. 
lbs. 
100 
100 
160 
120 
3rd, 4th, 5th, & 6th Courses . . 
200 
150 
2 B 2 
