594 
Rotation of Crops. 
the first, and of the tenth and eleventh courses are excluded 
from the averages to which attention will chiefly be confined. 
In this Table, however, as well as in those relating, respectively, 
to the barley and the wheat, averages are given at the foot of 
each division of the Tables, not only for the eight intermediate 
courses — second to ninth, but also for the two succeeding courses 
— tenth and eleventh, for which potash, soda, and magnesia were 
used as well as superphosphate. But, for the leguminous crops 
the averages are, for reasons that will be explained, taken dif- 
ferently. 
The first point to notice in the results is that, under each 
condition as to manuring, there is very great variation in the 
amount of produce from year to year according to the seasons. 
Thus, in 1868, the crop entirely failed on all the plots, although 
seed was sown twice. Again, whilst the complex manure con- 
taining nitrogen yielded more than 22 tons of roots in 1880, the 
same manure gave little more than 4 tons in 1860 ; the average 
yield over the eight courses being about 13£ tons. Against 
this, the average by superphosphate alone ranged from about 
6^ to about tons; whilst without manure there was an 
average of only about 1 ton. 
Referring to this last result, it is particularly to be observed 
that this assumed restorative crop yields practically no produce 
at all when grown without manure. 
The plot with superphosphate alone gives very much more 
than that without manure, but still very much less than an 
average agricultural crop. The increase, such as it was, was 
largely due to the greatly increased development of feeding-root 
within the surface-soil under the influence of the phosphatic 
manure ; and the necessary nitrogen, beyond the small amount 
of combined nitrogen annually coming down in rain and the 
minor aqueous deposits from the atmosphere, has doubtless been 
gathered under the influence of the increased root-development 
from the previous accumulations within the soil itself. There 
is, in fact, perhaps no agricultural practice by which what is 
termed the condition of land, that is the readily available fer- 
tility due to recent accumulations, can be so rapidly exhausted 
as by growing turnips on it by superphosphate alone — provided 
of course that the seasons are favourable. 
Compared with the produce with superphosphate alone, the 
mixed manure, supplying, besides superphosphate, not only 
salts of potash, soda, and magnesia, but a liberal amount 
of nitrogen, yielded, on the average of the eight courses, nearly 
twice as much, or between 13 and 14 tons of roots; though, as 
already pointed out, it yielded in some seasons over 20 tons per 
acre. There can be no doubt that, the necessary mineral con- 
