TOMATOES

SEEDLING PROPAGATION

GrowNurs propagates tomatoes via seedling propagation.

At GrowNurs we propagate our tomato seedlings via Hydroponics.Hydroponics is the process of growing a plant in a liquid with added nutrients but without the presence of soil.

Tomatoes grown via hydroponics

We use Hydroponics because there  are many advantages using this technique,the biggest of which is a greatly increased rate of growth within our plants.Our plant mature faster and produce up to 30 percent more than the same plant grown in soil.

The reason for this is because the plants will not have to work hard to obtain nutrients since there is a continual supply of nutrients available via the solution being pumped through the system.This allows the plant to focus more on growing upstairs instead of expanding the root system downstairs.

A hydroponic system uses less water than soil based plants because the system is enclosed,which results in less evaporation.Hydroponics is better for the environment because it reduces waste and pollution from soil runoff and since GRowNurs strives to be Eco-friendly,this is the perfect propagation technique to use.

pH CONTROL

All of this is possible through careful control of the nutrient solution and pH levels.The pH strongly influences plant growth therefore it is important to keep the pH in the proper range in order to produce the best yields of high quality. The optimum pH range for tomato production is 6.2 to 6.8.

PROCESS

At GrowNurs we have two greenhouses when it comes to propagating tomatoes,one is the seedling greenhouse and the other the propagation greenhouse.

We ensure that our seedling greenhouse is clean and disinfested prior to use.We make sure that the seeds we use to propagate the tomatoes are fresh seeds to avoid having reduced germination rates and vigour.

We seed our crop approximately around early November and the seeds is placed directly into rockwool(rooting medium)that has been soaked with a seedling feed solution with an electrical conductivity (E.C.) of 0.5 mmho , a pH of 5.8 and a temperature of 25 to 26 degrees Celsius. The rockwool plugs is not allowed to dry out. The seedling feed solution is used to wet the plugs as required (The goal is to maintain levels in the plugs without water logging).

Many things are maintained will seedlings are growing like:

• The temperature to the root zone is maintained at constant temperature of 25 to 26 degrees Celsius for the first two weeks while the seeds are germinating and young seedlings begin to establish.
• Air temperature also maintained at 25 degrees Celsius.
• Relative humidity of the nursery is maintained at 75 to 80% until the seedlings have emerged.
• Supplemental light is applied to the emerging seedling at 160 Watts/m2 for 16 to 18 hours per day 
• Once the seedlings have emerged the rootzone temperature is reduced to 23 degrees Celsius and the air temperature is maintained at 25 degrees Celsius. 
• The relative humidity is reduced to 70 to 75%
• Supplemental CO2 is delivered to ensure a target of 800 to 1000 ppm
• Seedlings are misted once a day for the first 4 days after emergence and this is controlled by the computer operated facilities( for more information about our computer operated facilities check out our infrastructure page).
• Root zone temperature are maintained using our bottom heating systems,which are in close contact to rockwool plugs.

TRANSPLANTING INTO THE PRODUCTION GREENHOUSE

Our tomato seedlings are usually ready to be transplanted into the greenhouse at 5-6 weeks of age.At this time the plants will have 7 to 8 true leaves.When transplanting our tomato plants into the production greenhouse,we put place the plants in direct contact with our growing medium(sawdust) when a number of roots are developing through the bottom of the rockwool blocks the seed was initially planted in.The goal is to ensure that the roots go directly into the sawdust to ensure firm rooting. But before we place the plants in direct contact with the sawdust,we first saturate the sawdust with feed solution for one week prior to the transplant so that the E.C. in the solution is the same as the rockwool block of the seedling and allows for complete wetting of the sawdust. This ensures that there is a constant environment between the block and the media that they are growing into. The sawdust  bags are slit for drainage immediately after the young tomato plants are placed onto the sawdust medium.We also ensure that the media is at the right temperature before transplanting the plants to it( at 20 degree Celsius).

MAINTENANCE OF THE ENVIRONMENTAL CONDITIONS
Once the plants are placed on the sawdust:

• We ensure that the air temperatures are maintained at 20 degrees Celsius day and night.
• A relative humidity of 75 percent 
• A liquid CO2 supplementation to 800 to 1000 ppm 
• Root-zone temperature is a stable 20 degrees Celsius

One week of transplanting we drop the night temperature to reach a minimum 18 degrees Celsius and maintain the 24 hour average temperature at 19.5 degrees Celsius.

All of the above mentioned points are computer controlled by our computer operated facilities.
(for more information about our computer operated facilities, check out our infrastructure page).


IRRIGATION
We have a precise schedule followed when it comes to irrigating the young tomato plants.A precise irrigation schedule ensures plant establishment and development of the root system.

Young tomato plants being irrigated

• 
  We schedule 7 irrigation events per day of about 30 ml per event starting at 9:00 am and ending at 3:00 pm.

• This strategy allows for the application of adequate amount of water throughout the day,but also times the delivery of water so that the roots grow to actively search for water between the watering events. 

At GrowNurs we try and to maintain a balance between vegetative and generative growth. This allows us to maintain a maximum sustainable yield of high value tomatoes for profit.

To vegetative:

• If the plants become to vegetative, we increase the stress on the plant by raising the 24 hour average temperature by 1 degree Celsius for a period of time,or modify the watering schedule to increase the duration between watering events( strategy is to adjust the timing of the watering events,not the amount of water delivered to the plants)

• Once the plants have been brought back into balance the temperature settings and watering schedules return back to normal.

To generative:

• This approach is the reverse to the one mentioned above. The 24 hour average temperature id reduced by 1 or 1.5 degree Celsius and the watering schedule is adjusted to deliver more frequent waterings. The idea is to reduce the stress on the plant.

PLANT TRAINING

Image of the setup of our plant training mechanism

• Tomato plants are trained to one stem that is physically supported by twine woven around wooden stakes to support unpruned plants as they grow.
• The twines are attached to the young plants by plastic "tomato clips" at about one week after transplanting.
• Once the plants are clipped, the next procedure is to lean the tomato plants into the direction that they will eventually be trained along the row.

PRUNING

• GrowNurs is a large propagation nursery therefore we have many workers at our nursery and each worker is assigned to an area in the greenhouse where they are responsible for pruning.

• The primary pruning tasks are the removal of lateral shoots,twisting the twine around the lengthening stem and Truss pruning.

• Pruning out the laterals and twisting the supporting twine is usually done twice a week.The lateral stems are pruned as soon as they can be distinguished from the primary stem.

• At GrowNurs we use a technique called Truss Pruning when pruning our tomato plants.It is required during the twisting and pruning events.

• Truss pruning involves the removal of young fruit from the truss as a technique to maintain optimum plant balance.It ensures that the plant does not try to fill too many fruit and also that the fruit left on the plant can reach their maximum size potential.