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Wisconsin State Horticultural Society / Annual report of the Wisconsin State Horticultural Society for the year ending July 1, 1921
Vol. LI (1921)

Roberts, R. H.
Off-year apple bearing,   pp. 72-78 PDF (1.8 MB)

Page 72

By PROF. R. H. RoBERTs, College of Agriculture.
Ladies and Gentlemen: We will begin with the proposition
that off-year bearing is due to nutritional conditions of the trees.
Now, many of you, as I know your orchards, doubtless think that
we are overstating the matter, for certainly the regularity with
which your trees have an off-year, might give you cause to think
that an off-year is not due to the lack of feeding, but is due
more to hereditary characters. I ask, however, that you bear
with me while I present some of the evidence which we have
collected that has caused us to arrive at the above conclusion.
We want to consider the question of blossom bud formation
and not very much about fruiting, although the latter is the thing
that you are certainly interested in from the economic stand-
point. As bud formation or fruitfulness has been shown pretty
clearly to be dependent upon the composition of the wood of
the trees, I want to consider this in considerable detail, in order
to make our position in the matter clear. If you are familiar
with the work of Kraus and Kraybill, which is given in Oregon
Experiment Station Bulletin 149, you will already have in mind
much of what we want to say of the relation between growth
and fruiting. If you are not familiar with it, and you grow any
trees whatsoever, you had better get that bulletin. The idea that
these workers present in explanation of fruitfulness in plants,
working with the tomato, is a most important matter in helping
the grower to understand how his trees are growing, and to help
him in deciding upon needed cultural practices.
Stated briefly, the proposition which they put forth is some-
thing like this. A plant has two kinds of food. One of these it
manufactures by its leaves from materials obtained from the air,
and soil moisture. An example of this type of food is the sugar
such as we get out of the sugar maple. We call this class of
materials carbohydrates. The other type of material obtained by
the plant is from the soil, as salts of nitrogen and phosphorus.
Kraus and Kraybill found that with tomatoes there are two kinds
of unfruitful plants, either the one which is over-vegetative, or
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