The amides are also at their highest on the plots which
show immaturity because of the use of large quantities of
nitrogen, and especially of nitrate of soda; on the contrary,
the use of potash at once diminishes the proportion of
amides. The proportion of nitrates present is less affected
by the manuring, but it is highest when an excessive amount
of nitrogenous manure is used, or when nitrate of soda supplies
the nitrogen in the manure, and is usually diminished by the
use of a free supply of potash.
Speaking generally, then, it will be seen that though the
composition of mangels is not greatly influenced by manuring,
yet certain factors go together. Highly nitrogenous manure,
especially when the nitrogen is in the form of nitrate of soda,
produce large and watery roots, whose immaturity is reflected
in the low quotient of purity, the high glucose coefficient, the
high content of nitrogenous matters, of which again a large
proportion is in the form of amides and nitrates. If the
nitrogen is in excess and the mineral manures are deficient
these differences are intensified, whereas an abundant supply
of potash tends to produce a more normal root.
PRACTICAL CONCLUSIONS 119

Practical Conclusions

Looking at the results of the experiments at Rothamsted
on the continuous growth of mangels with various manures
for twenty-seven years, from the point of view of the practical
farmer the following general conclusions can be drawn : —

1. Mangels can be grown continuously on the same land
without injuring the tilth of the land or the health of the crop.
2. A liberal dressing of farmyard manure forms the best
basis of the manure for mangels.
