|
| |
Information Courtesy of :
PLANT BALANCE
Maintaining plant balance between generative (=fruit development and bearing
stage) and vegetative stages are very important in the beginning of the season
for DRK 452. Each of the different types of tomatoes has its own
characteristics. Beef tomatoes like DRK 452 tend to be generative and put a lot
of energy into the fruits. Round tomatoes (60 to 90 grams fruit size) have this
to a lesser extent. Intermediate varieties (120 to 160 grams) have a tendency to
become very vegetative and not work very hard on the fruits until the 5th truss
or so. But regardless of the plant type, the plant habit we want in the first
months is the same: a generative plant with a good color, which is making small
cells with a high dry matter content, and with a good balance in dry matter
distribution between growing shoots and fruits. The plants must have adequate
leaf area and the stem must have the same thickness for the first months. How do
we create such a plant?
WATERING
A block/slab that is too wet can result in a strongly vegetative plant. Such a
plant will have large weak cells and be more susceptible to Botrytis. Remember -
reducing water intake will give a generative plant and stimulate root
development; increasing water uptake will produce a more vegetative plant and
help the roots take up water and nutrients.
The young transplant:
-in the vegetative stage (i.e. prior to flowering), make sure to give enough
water
-when flowering starts, give less water (more generative)
-after flowers have opened fully, give more water again.
When the plant is placed on the slab:
-give frequent watering of small quantities until the plant is fixed onto the
slab (only a few days).
-Keep the mat on the dry side until the 4th truss is flowering. (be careful and
don't let the slab dry out).
-When the bottom fruits have reached a size of 3 cm, then you irrigate fully.
-As a general rule water uptake is determined by: global radiation heating and
plant length, until week 5. In Eastern Canada growers will usually irrigate at
the rate of 2 ml/joules/cm2 per square meter of greenhouse space.
EC
-with the transplant give a EC of 3-3.5 mS/cm
-raise the EC gradually to 4-5
-when plant is flowering, the EC should be 3-3.5
-when plants have been planted, the pot EC should be higher than the mat EC
-after the 2nd and 3rd trusses have flowered, irrigate with EC 2.8
TEMPERATURES
Four week old plants that have just arrived at the nursery are given day:night
temperatures of 20:20 C for the first few days (the later the planting and the
higher the light level, the higher the average temperature for the first days
(21:21 or 22:22 C are not uncommon). These temperatures will steer the young
plant towards more rapid development.
At 6 weeks the recommended temperatures are 19:19 C
At 8 weeks grow at 18:17C. This temperature will cause the plant to become more
generative.
Temperatures up until the flowering of the first truss are variable and
dependent on the light level. When the first truss starts to flower, the
temperature must be lowered to a 24 hour average of 18 C. If necessary a
difference in day:night temperature should be created to keep the plant
generative (e.g. 19:17C). If the truss is pointing upwards, then the average
temperature is too high.
The rate of development of the plant depends on the temperature. The higher the
temperature, faster the rate of development is. Under low light conditions a
high temperature can give a weaker and thinner plant because the energy made by
photosynthesis is inadequate for the rate of development. A young plant will use
the available photosynthetic product in the first place for the maintenance and
growth of the plant, secondly for the roots and thirdly to form the fruits. A
temperature too high in relation to the light level will cause the young plant
to spend all its energy on plant maintenance and leave too little for roots
and/or trusses.
In general for a December 25 to January 15 sowing the advised temperatures to
grow the crop are:
More than 100 Joules/cm/day =18C 24 hr average
More than 200 joules/cm/day =19C 24 hr ave.
For long dark periods at less than 100 joules = 17C 24 ave.
For earlier sowing (Nov 5 to Nov 20) average 24 temperatures should be raised by
0.5C.
EXTRA SIDE SHOOT
Extra side shoots are left on the plant to obtain enough foliage to maintain
good fruit quality during the summer. Growers who grow short spring and fall
crops usually do not consider extra stems.
Assuming a start of 55 cm planting distance, the most common method is leave a
side shoot (around March 10) every 4th plant. Stem density will then be 45 to 48
cm in the row.
TRUSS SUPPORTS IMPROVES QUALITY
The occurrence of bent truss stems is common in the beginning of the spring
crop. Most growers will support the first 4 to 5 trusses with plastic supports.
The prevention of cluster stem bending will improve fruit quality and size and
result in better plant control. An alternative method is scraping the underside
of the truss stem from its connection to the main stem to half-way up the truss
stem. This is usually done when the first flower starts to show. This procedure
will cost 17 hours per hectare per week.
??
|
