| dc.description.abstract | The production of black spruce ( Picea mariana (Mill.)
B.S.P.) bare root stock in Ontario nurseries presents two
main problems. First, seedlings at the end of the first
growing season are small, and thus susceptible to frost
heaving. Second, it takes a long time, 3 years, to produce
shippable seedlings. Trying to solve these problems the
Ministry of Natural Resources Thunder Bay Nursery is
testing an accelerated transplant system. Seedlings are
sown in a greenhouse in a mini-container and after 10 weeks
are transplanted outdoors for two growing seasons. There is
a winter and a summer crop from the greenhouse each year.
The objective of this paper was to evaluate the effect of 3
factors on summer crop seedlings. The 3 factors were SOWING
DATE (levels: July 5, 15, 25, and August 4), the duration
of an initial 18-h LONG DAY treatment (levels: 7, 10, or 13
weeks), and the duration of a subsequent 8-h SHORT DAY
treatment (levels 0, 6, or 12 days). Finally, all
seedlings were held under natural photoperiod until the
total length of the SHORT DAY and natural photoperiod
treatments was 11 weeks. Bud initiation was monitored
during this 11 week period. Bud diameter, number of
primordia, basal caliper, and root dry weight were measured
immediately prior to placing the seedlings in cold storage
for the winter. LONG DAY was the most important factor.
Seedlings that received the ten-week LONG DAY treatment gave the
best response. Even though 13-week LONG DAY seedlings
were significantly taller, 10-week specimens showed a
similar bud diameter and basal caliper, as well as
a significantly heavier root dry weight, and more
primordia. Eventually, the containers were too small for
13-week LONG DAY seedlings that showed a potbound
situation. Although there were some significant
differences, the various levels of the factors SOWING DATE
and SHORT DAY did not produce any considerable effect on
the growing regime. At the end of the first growing season
in nursery beds, seedlings from the best treatment
combinations of the summer crop reached almost a shippable
size. This confirms the feasibility of the studied system
to produce bare root stock in two years or less. | |
