ks where the
water holding capacity of the soil was low, the cover died over the tree
root feeding spaces. Some may have said that the trees were having a
toxic effect upon the soil. This was not the case for, in 1932 and 1933,
both years of plenty of moisture supply, the covers have grown well
around the trees in these blocks.

I shall now ask you to refer to the conclusions on page 3 of our
Bulletin No. 294, issued by The Pennsylvania State College, which has
just been distributed to you. These conclusions are, of course, based
upon our work in an apple orchard but I believe they will apply closely
to the management of nut orchards.

Lessons from Fertility Studies in the Experiment Orchard

Most of the experiments in this orchard have now completed 25 years;
there have been few changes and these minor ones. Certain lessons may be
drawn from this quarter century of research:

1. The fertility of an orchard soil is more than its plant food content.
It involves the nature of the soil, its depth and topography, its
previous treatment, the use of fertilizers and manures, the amount and
nature of the cultivation and the covers or sods grown. Fertilizers are
only part of the problem of soil fertility.

2. In this orchard any treatment that has influenced the trees at all
has done so in the following order: first, the cover crops; perhaps
several years later, leaf color; shortly after, branch growth and
circumference increase; and last of all, yield.

3. The reason for this sequence of results is that the treatments,
whether chemical fertilizers, manure, or cover crops, have influenced
yields chiefly by changing the organic matter content of the soil; that
is, those treatments which have resulted in the production of larger
cover crops have ultimately resulted in the production of more fruit.

4. The organic content of the soil has been a considerable factor in
determining the amount of water in this soil. Those treatments which
have built up the organic content have kept the soil in condition to
soak up rainfall rather than to lose it by surface run-off. A larger
water supply, in turn, has produced more cover crops.

5. The site of this orchard seems nearly level to the casual eye; yet
slope, with its accompanying erosion, together with differences in depth
of soil, have created nearly as large differences in growth and yield as
any treatment. Good treatments have nearly offset the initial
disadvantage of poor soi