t of Nitrogen recovered in Increase of Crop._

With regard to the amount of nitrogen recovered in the increased crop of
mangel and roots when manured with different nitrogenous manures, it was
found at Rothamsted, as an average of six years, that the following
percentages of nitrogen were recovered: When nitrate of soda was
applied, 60 per cent of the nitrogen it contained was recovered in the
increased crop; when ammonia salts were applied, 52 per cent; when
rape-cake was used, 50 per cent; and when a mixture of rape-cake and
ammonia salts was used, 46 per cent.

It may be pointed out that the influence of season and climate on the
composition of root crops is very great--greater, indeed, than on any
other crop. Like oats, turnips grow better in Scotland than in England,
the moister climate of the former country being more suitable for their
maximum development, and hence the economy of maximum dressings in
Scotland.

_Norfolk Experiments._

In conclusion, a few words may be said on the Norfolk experiments,
carried out under the direction of Mr Cooke for the purpose of
ascertaining the best and most economical manure for mangels and swedes
on different Norfolk soils. In most of these experiments it was found
that superphosphate had not much effect in producing increase of crop in
the case of mangels; that the best nitrogenous manure was nitrate of
soda; and that on the whole it was not economical to apply farmyard
manure at the rate of more than 10 tons per acre. It was further found
that, although either potash or common salt gave a decided increase in
weight of roots, it was not necessary to give both these manures at
once, either of them being about as effective as the other.

Mr Cooke recommends the following manures as best suited for
mangels--viz., 2 cwt. nitrate, 3 cwt. common salt, and 2 cwt.
superphosphate. Upon certain soils peculiarly adapted to mangels, and in
warm localities where larger crops than 25 to 30 tons per acre are
habitually grown, it would probably pay to increase or to double the
above quantity of nitrate of soda. Ten tons of farmyard manure may, if
preferred, be substituted for all or a part of the nitrate of soda, or
may even be used in addition to it, according to the resources of the
farmer in respect of it, and the return he desires to get from the dung
in the first year of application or in future ones. It is best to apply
the nitrate of soda in two instalments--half at the time o