Results on nut yield and nut quality for the 132 sample trees have been
condensed to the presentation in Table 1. For the six-year period the
average tree in this study had a diameter of 13.3 inches and yielded 33
pounds of hulled, dry nuts a year. The yield of common black walnut
trees in the Tennessee Valley is characterized by extreme variation.
Tree size, of course, influences nut yield. One-half of the yields from
a 6-inch diameter tree ranged from no crop to 4 pounds of hulled, dry
nuts; whereas half the yields from a 22-inch tree ranged from 40 to 100
pounds. A yield of less than one-half pound of hulled, dry walnuts was
considered "no crop". Some individual trees had unusually high or low
yields. The outstanding bearer was tree 117. It had the highest average
yield for the six-year period, and the heaviest crop of hulled, dry nuts
for any single year. During the six years this tree yielded 953 pounds
of dry, hulled nuts and 194 pounds of kernels--truly outstanding
production for a common black walnut tree. Another notable bearer, tree
100, yielded 916 pounds of nuts and 189 pounds of kernels. However, this
tree was almost 11 inches larger in diameter than tree 117. The
exceptional bearers in each diameter class also had the highest single
nut crops. The other extreme is characterized by low yields. Crops were
lacking or insignificant for trees 60, 63, 211, and 221. Tree 37, with
a 19.7-inch diameter, bore only one crop of 31 pounds during the entire
six-year period. This tree has no value for nut production but would
yield a good sawlog.
Variation of yield by seasons and locality was examined by grouping the
132 sample trees into six localities of 22 trees each. Greater variation
in averages by crop years existed than averages by tree location groups.
However, some variation was found between the eastern and western
portions of the Tennessee Valley.
Indications on bearing habits were obtained for a six-year period on 96
trees, Nos. 1 through 140 (Table 1). Crop records for each of these
trees were examined for relatively high and low yield by seasons.
Convincing evidence on the alternation of bearing has accumulated during
this six-year period with 46 percent of the trees having lighter crops
every other year. Of these, 28 trees bore lighter crops in the odd years
and 16 trees bore lighter crops in the even years. Tree 117, previously
mentioned as outstanding in regard to yield, produced lighter crops in
1940, 1942, and 1944. This tree is located in west Tennessee.
Walnut trees bearing lighter crops in 1941, 1943, and 1945 are more
abundant in the eastern than in the western portion of the Tennessee
Valley. This occurrence undoubtedly accounts for much of the variation
found between the eastern and western portions.
Four other yield patterns were recognized in 30 per cent of the trees.
These indicate the existence of uniform annual crops and three-year
cyclic bearing of black walnut. The bearing habits of the remaining 24
per cent of the trees is considered merely irregular, since definite
patterns cannot be recognized until bearing records cover a longer
period of years.