If the quantity applied is too small to meet the demands of the crop,
unless all seasonal conditions are favorable, the chances are that the
results will not be completely satisfactory, as weather conditions
are not likely to be perfect; it may be too wet or too dry, too cold
or too hot, and hence, during certain periods, the plants would not
be able to obtain their food--that is, it would be impossible for the
plant to absorb always its food uniformly, or in such amounts and at
such times as would result in the best development of the plant. In
all cases an amount should be applied that would exceed the needed
requirement under perfect conditions.
[Illustration: LIQUID MANURE IS ONE OF THE BEST ACTING FERTILISERS]
In the second place, if the quantity found to be necessary for a
definite increase of crop, under average conditions, were all applied
at once, say in the early spring, a greater opportunity would be
offered for losses from leaching than would be the case if the material
were given in successive dressings, so that the losses due to the
escape of the nitrogen would be minimized; on the other hand, if no
losses occurred, the plant might take up more than could be utilized in
a normal development, thus defeating the purpose, because resulting in
a product of less commercial value. This would apply, of course, only
in the case of those crops that are injured by abnormal development in
certain directions, as, for example, too large a proportion of straw
in cereal grains, too large a root in sugar beets, etc. All these
difficulties may be obviated by a fractional application, or, in other
words, by supplying the nitrogen at the time and in the quantity best
adapted for the plant and for the purpose in view in its growth. The
results from the use of nitrogen may be also unsatisfactory if nitrogen
only of the elements essential is used. The best results from the use
of nitrate can come only when there exist in the soil, or are applied
with it, sufficient amounts of the mineral elements to enable the plant
to obtain a food suited to its needs--nitrogen is but one element of
plant food.--(N. J. A. E. Sta., 157.)