is certain in some of the experiments and strongly indicated in
others that the soil is having a one-sided wear--that only one or a
very few of the elements of fertility are lacking. The element most
frequently lacking is nitrogen. Exception will probably be found in
very light sands or gravels which are often deficient in potash and
the phosphates; or on soils so shallow or of such mechanical texture
that the root range of the vine is limited; or in soils so wet or so
dry as to limit the root range or prevent biological activities. These
exceptions mean, as a rule, that the soils possessing the unfavorable
qualities are unfitted for grape-growing. The grape-grower should try
to discover which of the fertilizing elements his soil lacks and not
waste by using elements not needed.

_Grape soils are often uneven._

The marked unevenness of the soil in the seven vineyards in which
these experiments were carried on, as indicated by the crops and the
effects of the fertilizers, furnishes food for thought to
grape-growers. Maximum profits cannot be approached in vineyards in
which the soil is as uneven as in these, which were in every case
selected because there was an appearance of uniformity. A problem
before grape-growers is to make uniform all conditions in their
vineyards, and the vines must be kept free from pests if fertilizers
are to be profitably used.

_How a grape-grower may know when his vines need fertilizers._

A grape-grower may assume that his vines do not need fertilizers if
they are vigorous and making a fair annual growth. When the vineyard
is found to be failing in vigor, the first step to be taken is to make
sure that the drainage is good; the second step, to control insect and
fungous pests; the third, to give tillage and good care; and the
fourth step is to apply fertilizers if they be found necessary. Few
vineyards will be found to require a complete fertilizer. What the
special requirements of a vineyard are can be ascertained only by
experiment and are probably not ascertainable by analyses of the soil.
This experiment furnishes suggestions as to how the grape-grower may
test the value of fertilizers in his own vineyard.

_Applying fertilizers._

When it is certain that vines need fertilization, and what is wanted
is known, the fertilizers should be put on in the spring and be worked
in by the spring cultivation. Stable manure should be plowed under.
Grape roots forage throughout the whole top