Rotation of Crops. 
597 
The accompanying figures represent selected typical Swedish 
turnip-plants, grown in 1892 — without manure, with the mixed 
mineral manure alone, and with the mixed mineral and nitro- 
genous manure* Each plant was fixed upon a scaled back- 
ground and so photographed, and the figures as given are about 
one-twentieth natural size, and strictly comparable. The quan- 
tities of produce recorded show that without manure it was less, 
but that by each of the two descriptions of manure it was con- 
siderably more, than the average of the preceding courses ; and 
both the reversion to the uncultivated condition without manure, 
and the increased growth under the influence of each of the 
manures, are strikingly illustrated, both by the figures and by 
the amounts of produce given. Indeed, the results conclusively 
show how artificial a product is the cultivated root-crop, and how 
dependent it is for its successful growth on an abundant supply of 
available food — nitrogenous as well as mineral— within the soil. 
The Barley Crops. 
Table II. gives the produce of barley, the second crop of 
the course, and therefore always succeeding the roots, in each of 
the eleven years in which it was grown, in precisely the same form 
as that of the Swedish turnips recorded in Table I. : the upper 
division giving the grain per acre, the middle division the straw, 
and the lower one the total produce, grain and straw together. 
As in the case of the root-crops, so in that of the barley, the 
produce in the first course is excluded from the calculation of 
the averages to which reference will chiefly be made. Indeed, the 
results of the first year of barley confirm the conclusion that the 
land was in somewhat high condition due to recent accumula- 
tions. The produce of the tenth and eleventh courses is also ex- 
cluded from the averages, on account of the change of manure on 
the superphosphate plot for the tenth and succeeding courses. 
Referring, however, first to the results of each of the eleven 
years, it is seen that, under each condition of manuring, or other 
treatment, there is very great variation in the amount of produce 
from year to year, due to variations in the characters of the 
seasons. Thus, without manure, the average produce over the 
eight courses was about 30 bushels per acre, whilst in 1857 it 
was in each case more than 40 bushels, and in some considerably 
more ; but in 1869 and in 1873 it was not much over 20 bushels, 
and in the last two courses considerably less than 20. A glance 
down the columns recording the produce on the manured plots 
will show that in their case also there was a wide range in 
amount above and below the averages, according to season. 
Referring now to the average produce of the eight courses 
(second to ninth), the first point to notice is, that whilst the 
