- In 1960 tests were initiated on the Marion blackberry (Rubus
hybrid) to study the effect of (1) plant spacing, (2) time of training
canes to the trellis and (3) amount of cane to train to the trellis with
regard to fruit bud formation and total yield.
Plant spacing varied with 2.5, 5 and 10 feet between plants in
the row. Time of training the canes to the trellis was approximately
the middle of the months of August, September, October and February.
The amount of cane trained on the trellis was either the entire length
of all sound canes or only enough of each cane to reach the adjacent
Total yield of fruit, fruit spur determinations, time of fruit
bud formation, leaf size and number and carbohydrate:nitrogen ratio of
leaves were studied and/or measured.
Although yield differences were greatest in the early years of
the planting, 4-year averages indicate that closer spacing of plants
resulted in highly significant increases.
August-trained canes produced the highest yields, followed in
order by February, September and October.
Differences in yield between the length of canes trained were
very small and generally non-significant. When more cane grox<rth was
trained, a corresponding increase in training time was required,
particularly at the closer plant spacings.
August and September training of canes stimulated the axillary
buds to elongate and produce lateral growth. These laterals on August-trained
canes matured enough to allow the formation of fruit buds,
while laterals on September-trained canes were generally too succulent
to form fruit buds.
August-trained canes produced more fruit spurs per foot of row
than February-trained canes. No difference in number of flower buds
per fruit spur occurred between August and February training.
Leaf counts on November 1 indicated that trellis training done
in August produced more trifoliate leaves per foot of row than when
the canes remained on the ground. Trifoliate leaves from ground-level
training were larger.
Axillary buds were collected at 2-week intervals starting on
August 1 and continuing until November 15 for the purpose of determining
the time of fruit bud formation. The canes were divided into three
sections, (1) basal, (2) mid-and (3) terminal, and each sampled
separately. Buds from trellis-level training changed little during
August and September; however, on October 2, buds from the terminal area
only of canes and laterals were showing elongation. By mid-October,
buds from all areas of the cane were showing an elongation of the apex.
The first and only floral structure, expressed as a broadening and
flattening of the apex, was observed in terminal section buds sampled
on November 15. In contrast, basal and mid-section buds from canes
trained along the ground during the summer showed an elongation of the
apex by October 2, and by November 15 well defined floral structures
were observed. Buds from the terminal section of cane were beginning
to show some elongation by mid-November.
Carbohydrate and nitrogen determinations were made on trifoliate
leaves sampled from various loci on the canes on November 1. Older
leaves, regardless of plant spacing or time of training, had the lowest
nitrogen content. Carbohydrate content of leaves was quite variable.
The C:N ratio was lowest for the 5-foot spacing in both trellis-level
and ground-level training. Leaves from the terminal area of the.canes
had the lowest C:N ratio.