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cont'd...Continuous Production Systems: Part I
by Erik Biksa
This is the first part in a series of articles that will enable growers to develop their indoor gardens and management practices so that they can harvest bigger yields per square foot, with the benefit of having harvests every 10 to 30 days.
A lot of gardeners may have raised their eyebrow when reading the above statement. Did the author make a type-o, has the author completely lost it or is there some new strain you don’t know about? Relax; the answer is none of the above. This is not a new growing method by any means, as ingenious growers have been facilitating perpetual harvests for years now. The technique appears to have been pioneered in greenhouse production, namely with leafy greens such as lettuce, herbs and cut flowers.
However, it’s time to take the foundation provided by perpetual harvesting methods pioneered in the greenhouse and build on it to create a high efficiency cropping system for the indoor gardener. Continuous Production Systems (CPS) should keep any gardener happy by creating routine management practices and ensuring that their next harvest is never more than a few days or weeks away from their last one.
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The six-inch intake is near crop level, and uses a special HEPA filter designed for use with inline fans to help prevent spores and insects from entering the sealed growing area. It further helps to diffuse cooler air as it enters the growing area, reducing the potential for shocking the plants with cold outside air.
As with many things in life, it all boils down to time management. The CPS grower needs to streamline their cropping schedule and practices for rooting cuttings, vegetative growth, flowering, ripening and harvesting. For CPS systems, the grower is required to maintain separate vegetative and flowering areas. These areas need only to be separate in the sense that they will require different photoperiods and environmental control. Light leaks from one area to another can be disastrous, so careful planning and construction is recommended. This series will outline modern grow room building techniques and practices that will help growers avoid making many common and costly mistakes.
However, before we get too far ahead, let’s talk a little more about what a CPS growing system is, and how you can begin to plan and construct yours.
Tommy Tomato (c'mon, SOMEONE sign up with TommyTomato!!) grows a variety of cut flowers that typically require 65 days of flowering before they reach maturity. The variety is a short-day flowering plant, so he can induce the flowering response anytime he wants by maintaining his plants in a 12/12 photoperiod. The variety can be grown as single stems by reducing the number of days spent in the vegetative photoperiod (18/6) or can grown as a larger, multiple branched specimen by allowing for more vegetative growth and manipulating the plant’s natural tendency to branch.
Either single stems or larger bushes are capable of producing bunches of high quality flowers; in fact, yields per square foot are similar. The advantage of single stems is less time in vegetation is required, which means they get into the flowering room quicker. Growing larger plants means having a lower numbers of plants to look after, and often with less labor and materials. Remember that when you grow single stems, you need to pack-in the plant numbers per square foot to get a sufficient amount of flowering sites per square foot versus larger, better-branched plants.
Tommy wants to keep the electrical bill low, and only wants to dedicate two 1000-watt lamps for the flowering area and 400 watts of lighting for vegetative growth with either high output fluorescents or with metal halide lighting. The size of the flowering area might range from three feet by two seven feet to 4.9 feet by 9.8 feet {Dunno WHAT he's talking about here, a 1k covers a 4 x 4 in flower. 4 x 8 - or something similar - is what Tommy should be playing with. Paddy} using the two HID lighting systems. For vegetative growth using 400 watts of lighting an area of 2.46 feet by three feet should be sufficient, especially if two levels are constructed by use of shelves and racking.
Alternatively, to reduce venting requirements and allow for efficient CO2 supplement in the vegetative chamber, high output T-5 fluorescents or LED lighting can be used to light the vegetative growing area. LED's emit virtually no heat, and the energy they use is converted into light energy very efficiently. LEDs also consume very little electricity; apparently 45 watts of good quality LED lighting can replace a conventional 250-watt HID system according to some manufacturers. The use of LEDs allows growers to create growth chambers that would not be possible due to size or venting constraints. This series will examine the use of LEDs, and their feasibility in all growth systems including CPS (Continuous Production Systems).
CPS is also well suited to larger, multiple lamp installations and can be adapted to larger applications by following the model outlined in this series of articles.
Tommy prefers to have bigger plants and fewer of them to simplify labor and ensure good yields. He usually grows four plants per 1000-watt lamp, and can continue to use this planting density in the CPS model. So, in total, there will be eight plants in the flowering area at all times, that’s four plants per light. The number of plants maintained in the flowering area can be streamlined over time in a CPS model, for example Tommy may find that he actually yields more by only maintaining six plants in the flowering area.
No matter how many plants he maintains, he will be harvesting a portion of them on a regular basis, and replacing them with new plants that are ready to flower, often on the same day.
Since the variety he prefers to grow requires 65 days of flowering, and he wants to maintain eight plants, Tommy will harvest two plants about every 16 days. So, in this CPS model he will have eight plants that are in four different stages of reproductive growth in the flowering room, dividing his crop into four distinct blocks, each containing two plants.
To supply the CPS flowering room with sizable and healthy plants ready for flowering every 16 days requires maintaining a tight propagation and vegetative growth cycle. To do this, Tommy starts new cuttings every 16 days and allows them the full 16 days to develop a healthy and vigorous root system. At the end of the 16 days of rooting, the cuttings are transplanted, and grow in an intensive vegetative environment for another 16 days. However, as soon as the rooted cuttings were transplanted for vegetative growth, Tommy started new cuttings at the same time that would be ready again in another 16 days to repeat the cycle over again.
In the vegetative area, every 16 days the following occurs:
* New cuttings are started
* Rooted cuttings are transplanted for vigorous production
* Vegetated plants are ready and transplanted for the flowering area
You can fine-tune your own CPS model for more or less frequent harvests with any number of plants. You can run your CPS set-up as tightly as having daily harvests and replacements or space it out to as much as a month a part. You just need to know how long the variety you grow takes to mature, and you can plan from there. Plants that gain more size in flowering are preferred, this way you can grow larger and fewer plants without having to spend too much time in the vegetative growth phase. If your variety produces slow vegetative growth, and does not gain much size in flowering, you can grow greater numbers of smaller plants, or widen the CPS window to 32 days instead of our example of 16 days.
If you widen the CPS window to 32 days in our example you will harvest four of the eight plants every 30 days instead of two of the eight plants every 16 days. You will get similar yields per plant, but the time between harvests will be greater. In the vegetative area, the plants can still root for 16 days, but will then get 32 days of vegetative growth instead of 16. You would also be vegging four plants for 32 days rather than two plants for 16 days.
The vegetative cycle, and the number of plants you maintain in it can be fine tuned over time. The most important thing is that you have the correct number of plants that are the right size for the flowering room available on a scheduled basis (in our example every 16 days) to replace the plants that you harvest on a scheduled and routine basis.
Don’t get a headache thinking too much about this yet, as it will become more apparent and simplified through the CPS series of articles.
As with any indoor gardening project, your success will be the result of a combination of the following factors:
* Having a suitable variety
* Good crop management
* The construction of the growing area
* Level of environmental control (light, air, water)
* Using high quality nutrients, additives and beneficials
In this series, you will be walked in a more or less step-by-step basis into establishing a successful CPS model of your own. Again, this model is only using two 1000-watt lights for flowering and 400 watts of lighting for the vegetative area, although you can adapt the CPS model to larger or smaller endeavors. An alternative light source can be used in the vegetative chamber such as T-5s or LEDs to reduce electrical consumption and cooling requirements. While in the flowering area, use a dimmable 1000-watt lamps or one 600-watt for the early flowering phase and one 1000-watt for the later flowering phase can be used to further reduce electrical consumption and venting requirements. An adjustable light mover could allow for the use only one 100-watt lamp or one 600-watt lamp for the flowering area, although yields per square foot of growing area may be slightly reduced in a trade-off for electrical savings. In some installations, it may be possible to use LEDs as lighting for the flowering area, and this series, we will look at the possibilities.
Before we can start to build anything, we need to carefully source our equipment and think about how we want to manage the growing environment, which includes light, temperature, air movement, CO2 levels and relative humidity.
For lighting, digital/electronic ballasts are an excellent choice. While the initial outlay can be more expensive versus conventional ballasts, the benefits greatly outweigh the extra investment at start up. One of the ballasts pictured is the next generation in HID lighting technology. {It's about the light, not the ballast. Digi ballast are NOT UL listed, and DO emit a very distinct line noise to the cable/electrical guy if he is working near your house. Quality mag ballasts are bullet proof. And virtually fire proof}
The unit runs completely cool to the touch and will automatically cool itself or even shut-off if overheating, all with visual display indicators that tell the grower exactly what the ballast is doing. The unit runs near silent and can be mounted in any position easily, as it weighs less than a book. An additional benefit is that the lamp can operate at distances of up to 75 feet away from the ballast unit. This can be of great benefit to growers, helping to create gardens of any scale, while keeping all lighting equipment in a centralized area. This cutting edge lighting technology also allows the unit to be plugged into any voltage from 90 volts to 270 volts without any changes made to the unit. It detects the input voltage, and strikes the lamp perfectly, bringing it to brilliance within about five minutes.
While conventional core and coil ballasts are inexpensive and have been reliable, electronic and digital ballasts can offer many advantages past their electrical savings and high output. In cooler climates, some growers may actually take advantage of the heat generated by core and coil ballasts to help warm their growing areas in cold months.
High quality air-cooled reflectors will improve the efficiency of any grow room including continuous production systems. They remove heat generated by lamps before it enters the growing area, and reflect the light downward in an intense and equidescent spread.
It is recommended that you get the highest quality lighting system that you can afford. There is no sense wasting the lumens you generate, because you pay for each and every one of them and they directly translate into the output capability of your conventional or CPS indoor garden.
Where short runs of lights are used, for example two lamps in a row, the air-cooling can be orientated directly in-line. Larger installations will require ducting “trees.” The reflectors pictured use a highly reflective aluminum insert that helps even light distribution from the ends as well as the sides of the lamp reflector. Although almost invisible to the human eye, the material is very finely textured to help diffuse light. High quality models feature tempered glass lens for safety and durability, and are hinged to allow for easy access and cleaning. Gaskets ensure that there is a tight seal between the reflector and the lens to prevent grow room air from escaping the area un-filtered.
In-line centrifugal fans are recommended for cooling, as they allow for variable speed control, which is one of the core benefits of this CPS model due to a special control that regulates the fan speed with cooling requirements. Two six inch or eight inch models (exhausts) and one four inch or six inch model (intake) are required for the number and wattage of lights outlined in this model. However, centrifugal fans are available in a range of outputs to suit any sized installation. Note the mounting of the in-line fans in this CPS model. Rubber straps are used to suspend the fans from the ceiling with sturdy hooks. This greatly reduces the noise and vibration associated with fans. This can be especially important when you or other must cohabitate with or near the growing area.
A high quality activated carbon filter is suspended at one corner of the CPS chamber for evacuation of warm and moist grow room air. At the opposite corner a HEPA filter designed for use with in-line fans prevents spores and insects from entering the growing area that might cause problems with crops. Both of these pieces of equipment are essential to ensuring that air coming in and out of the growing area is free from contaminants. To help prolong the life of the carbon filter, the model chosen has a removable and cleanable pre-filter. By cleaning the pre-filter periodically, fewer particulates will enter into the activated carbon matrix, extending the period that the unit can be used before requiring replacement.
For any sized installation, and especially for small to mid scale, but intensive CPS installations, a high degree of environmental control is recommended. At the heart of this model is a fan-speed controller that regulates the output of centrifugal fans based on grower day and night temperature set points. This device is rather ingenious, and should be a welcome addition to any grow room. Instead of having your fans come on full-bore thermostatically, then shutting off, the unit increases or decreases the fan speed as cooling requirements dictate. For example, if the day temperature exceeds the set point, the fans area is activated, but at a low and quiet speed. If this does not cool sufficiently, the unit will increase the fan speed slowly, until the area is cooled back down to the set point. It operates both a tight and soft mode, depending on the level of control you want to maintain.
The intake, exhaust fan (with carbon filter) and air-cooled lighting fan can all be coordinated by the device. Temperature control is very accurate using the remote probe supplied, with little or no significant temperature fluctuations from the grower day and nigh set points.
For safety and ease of use, high quality lighting timers/relays can be purchased pre-wired and are very user friendly. The grower simply needs to connect the two hot wires, ground and neutral (if applicable) to the easy to access lugs inside the unit following the diagram supplied. Now, simply connect this to your 240-volt power source (ensuring that it is safely off first), set the timer, and plug in your lights. These are proven devices that are backed by reputable manufacturers and make installing HID lighting much safer and easier. A lot of these units can be purchased for the same cost as building your own, but without all the guesswork and with added piece of mind.
For an increased degree of safety and reliability in your CPS installation, your timed lighting power relays trigger cord/plug can be connected to an additional controller that prevents hot lamp starts and shuts off the lighting system if the temperature exceeds the grower set-point. With this device, if the power is interrupted by either a power shortage, or by the device (to prevent overheating of the grow room due to equipment failure), the device will wait for 15 minutes after the room is cooled or power is restored before allowing the high power lighting relay to become activated. Conventional ballasts will not start and can be damaged as well as the lamps, if they do not have time to cool between being shut-off and being re-started.
Technologies where plastic films are concerned grow leaps and bounds. There are some excellent choices to be had in selecting a reflective material that reflects the maximum amount of light, while retaining all of the light energy to help the CPS installation operate more efficiently by helping to prevent radiant loss of light and heat energy. Typically, white films have been preferred to apply diffused reflective light, but the reflective film featured has both a silver reflective and a white reflective side, offering a choice. According to the manufacturer, the silver reflective side of this special film helps to convert reflected light into wavelengths that help crops perform better. To ensure light-tight installations, overlap the seams of the film six inches and seal with aluminum tape, as pictured. The reflective material for the walls and ceiling, and the thick heavy gauge reflective white poly for the flooring were carefully sourced from a European manufacturer to ensure that they were food grade materials and would not give off any gases that could be harmful to the crop.
So far, we have talked about some high tech cropping methods and cutting edge growing equipment. In the next few installments in this series of articles, we will see how it all comes together to help create the perfect controllable environment that is at the heart of continuous production systems. There will be plenty more to come on the actual construction of the vegetative and flowering chambers, the installation and management of the controls, ventilation and lighting. Plus, we will talk at some length about CPS management to ensure frequent and abundant harvests including important aspects such as the management of crop nutrients, additives and beneficials.
In the meantime, start to source your gear (lighting, fans, controls, filters) building materials or grow-hut and get ready to start planning your harvests as close together as you can manage. Continuous Production Systems are capable of providing you with as much harvest as you desire, as often as you want it; with a little bit of planning, expense and some work.
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