These are some of the young plants i will be growing, sweet peppers on the right, tomatoes in the middle and chillies to the right. There are also some plants called Pepino at the far right which are nicknamed melon pears because of their sweet soft fleshed fruits.
The plants have recently been inserted into the larger 4" rockwool blocks and have been kept under a gentle fluorescent light to let them develop their root system before intensifying the light, i'm using a T5 high output 8-way flourescent light because it produces lots of lightat a low temperature with low power comsumption and has a good spectrum of light for vegatative growth and i can choose between 4 and 8 lights. I'm keeping humidity high into the 70%'s to slow the transpiration rate. I use 2 HR50's for the whole greenhouse which is 75m2, they're linked up to a humidistat to control humidity.
As you can see the plants are sat on mesh grid this allows air to the underneath of the blocks. When roots reach the bottom and come into contact with the air the tip dies back.
Using the analogy of 'topping' a plant where you nip the growing tip off a plant to encourage side branch growth by changing the position of growth hormones in the plant. The same principles can be applied to the roots.
This technique is called air pruning and is something i will always do to get my plants established well enough to cope with environmental changes. Changes from the propagation stage to final planting position include greater light intensity, heat, air movement and amount of water recieved by the plant. Moving a plant too early will put too great a demand on it before it has developed and will stress it to the point of stunted growth, poor root development and risk of becoming disease infected. A well established plant will grow quicker and healthier and have potential to yield greater than one that isn't.
Note: All plant species and varieties among species have widely different root systems some thin some thick, some are abundant others are not.
A technique in commercial grows is to use a root-stock plant and to graft a favoured top part of a plant onto it. This means you use a variety of plant that has been bred to produce alot of roots and is disease resistant. That plant hasn't been bred for flavour or yield so to get the best of both worlds, they simply cut the top off and replace it with a plant that has been bred for flavour and yield. It's a technique i've not tried but am very interested in the benefits as you can choose the best phenotypic characteristic from two plants.
Here's an overview of the greenhouse with most of the plants just gone into the different systems. The humidifiers are going to play an important role in the early establishment stages as there will be less demand for water to be uptaken by the roots and will allow the plant to spend energy in root growth. A young plant with a healthy mass of roots will be more hardy and have a much higher yield potential.
Another way to maintain high humidity levels in the establishment stages is to use something like these propagation domes. I've used them on the IWS flood and drain and the IWS dripper systems because they are a perfect fit. They create a micro-climate where moisture generated from the pot and the plants leaves can't escape and so elevates the humidity levels inside. The vent on the top can be opened gradually to control the humidity levels, gently easing the plant into the surrounding environment. This ensures that the plant can withstand the humidity levels of the main room with minimum of stress.
On the left hand-side of this picture you can see the tomato plants in the autopot system. I've got coco fibre mixed with perlite as the growing medium but you can use rockwool cubes, mapito, serramis, fytocell or soil (anything with a good capillary action but has a good air content). At the minute the pots aren't connected to the water butt. Even though it is a self-watering system i choose to hand water for the first couple of weeks. This is because i do not want the plants to be overwatered at such an early stage. By hand watering i can allow the pot to dry out slightly before the next watering. This will increase the air content within the pot and lower the water saturation level creating a perfect environment for a young root system to grow in.
Everyone has their own ideas and methods for rooting plants in NFT systems. Working at a Aquaculture i get to hear them all and i'd say there's no set practice that will work the best everytime. What will work best everytime for one person doesn't mean it will definately work best for another. There are many irrigation patterns that people go through like 15mins on every hour and will increase the frequency as they get bigger. There are generally two types of people, people who overwater plants by either putting a plant on the system before its had chance to root properly and/or having their pump on too high a setting where it floods the tray and drowns the young roots. On the other hand you get people that try that hard to get as much air as possible to the roots by having a massive ammount of time between irrigations for a prolonged period despite having a good ammount of root mass in the block to begin with. Even though the block may feel wet still the pioneer roots that are on the tray will dry up and the demand on the plant may outweigh what is supplied to it thus stressing it and not allowing its roots to develop properly.
I've said it before that every plant has a different root system and every growroom environment is different therefore each time needs its own tweaking. I will only start with a plant that has an abundant ammount of roots in the block, that way it will cope better the environment change and ammount of water you throw at it. I've personnaly not had any problems with putting a well rooted plant on the system with a constant flow on a slight trickle. This is the way commercial greenhouses have done it for years to great success.
Aubergines in the amazon were a doddle because i didn't need to alter irrigation settings as the aeroponic method delivers an ideal ammount of water and air to the roots so i just left it sprinkling 24hrs.
Both the tomatoes on the high and low pressure drip feed systems were left to sit in pre-soaked rockwool and coco slabs. They didn't need an irrigation for a number of days. The slabs remained damp enough for up to 5 days before needing a watering, and that was only to prevent a ph or ec change. They weren't regularly irrigated till up to 2 weeks after hand or manually irrigating them. This let the root system develop so it can cope with the frequency of timed irrigations daily.
