e margins of the leaf
blade. Sometimes this chlorosis results in blotches, which may extend
for a considerable distance from the margin towards the mid-rib. This
stage is of short duration, as the tissues of marginal chlorotic areas
or those of the blotches soon die, roll up, and turn brown. Some leaves
show yellow blotchiness over most, if not all, of the surface and this
may develop into brown patches of dead tissue or the yellow leaves may
fall before the tissues die. The older leaves, those at the base of a
shoot, are generally the first to show chlorosis and scorch, and the
terminal leaves are the last to show such symptoms. On severely affected
trees all the leaves on a shoot may be scorched at the time scorching is
observed. Severely affected trees drop part or all of their leaves
prematurely. The leaves dropped are those that are scorched or that show
yellow blotches. Such trees do not make satisfactory growth, they set
few nuts, and the nuts are usually poorly filled at harvest. The
symptoms of scorch on filbert leaves are similar in many respects to
magnesium-deficiency symptoms on apple (1, 5, 6)[11] and tung leaves
(3).

Leaf Analyses[12]

No differences in appearance of the trees as regards leaf scorch were
noticed the first year after the differential fertilizer treatments were
applied. However, in late July and early August of the second season,
severe leaf scorch developed on the trees that had received potassium
alone or nitrogen plus potassium, and scorch developed to some extent on
the check trees. On August 15, 1950, leaf samples for chemical analyses
were taken from each tree in all replications and composited by
treatments into six samples. The data on the chemical composition of the
leaves as affected by the differential fertilizer treatments are given
in table 1.

These data show that the fertilizers applied to the trees were taken up
by them and that the composition of the leaves was significantly
affected. The trees in treatments 2, 3, and 6, which did not receive
nitrogen in the fertilizer, had lower percentages of nitrogen in the
leaves than those from the other plots. Their light green color
indicated that in the middle of August they were deficient in nitrogen
when its concentration was 2.3 percent or less.

=Table 1. Chemical composition (oven-dry basis) of filbert leaves
collected August 15, 1950, from fertilizer experiment, Beltsville, Md.=

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