What is Environmental Control?

The environment in the grow room is probably the single most important issue that you need to control. It is a simple fact that you need light, air, food and water to grow any plant, but the way you manage these systems will make a massive difference to what you ultimately yield, both in terms of quality and quantity. It is these systems that make up the environment in which your plant will be nourished and hopefully thrive, if you get them right at least!

Some of the remedies to environmental control issues are very simple and should always be the first things you consider before spending vast sums of money on introducing external control systems.  However, some of the things that Mother Nature throws at the grower can not be avoided or managed without investment in both the resources and the time required in order to resolve the problems you will face along the way.

Light

Light is required in order to stimulate the photosynthesis process that is required by most plants to produce a fruit or crop (rhubarb is a notable exception to this rule). The spectrum of light the plant requires changes over its life and this needs to be managed as part of the systems you put in place.

The amount of light changes thought out the life cycle as well (depending on what you are growing), if the plant comes from a  region away from the equator, it may require 18hrs of light in order to grow and prefer white light for this period of growth. During flower or bloom periods (and often in order to stimulate the change from growth to bloom) the plant may only require 12hrs of light. This cycle reflects the changing amount of light made available to the plant in nature through the natural change in day length.

If you are growing using the Sun you have everything you need as far as spectrum is concerned. However, you may not be able to get enough power of light consistently throughout the life cycle (lumens), or conversely, you may get too much (winter v's summer).

One of the contradictions that the grower must resolve is the need to get the lamp as close to the plant as possible in order to maximize the amount of Lumens (strength of light) made available, but if the lamp gets too close the heat it generates can scorch the plant and this, in turn, creates significant problems including shock and wilt.

Light Remedies

Use a heat shield to reflect the heat of the bulb back up to the reflector and therefore increase the distribution and diffusion of the light created. This has the benefit of preventing hot-spots directly beneath the bulb.

Extract the air from immediately around the light bulb so as to minimize the effects of the convected heat it creates. This will allow you to lower the light closer to the plants and therefore increase Lumen availability. Use either a extractor shade or place your extraction hose close to the plant.

Use a Growlux light bulb to ensure a full spectrum of light at all stages of growth and bloom, alternatively use Metal Halide for grow (white spectrum) and Sodium (Son-T or Son-T-Super) for bloom (yellow spectrum).

Mirror the seasonal changes in light the plant gets in nature, use 18hrs of light for grow and 12hrs for bloom.

Less is more! Use the strongest light you can without compromising the heat you generate. Use 250w or less for the grow room and 1000w to 400w for the bloom period. Remember that you may cause significant heat problems if you a strong light in a small room without the control systems in place to cope with the heat.

Air

Room Temperature

Ideally this should not be above 25˚C or below 15˚C, but the most important thing is not to allow large fluctuation. Target to keep your room around 20˚C with a +/- of no more than 2.5˚C

You need to consider different issues at different times of the year.

Summer – Too Hot!

The temperature of the air coming in to your room may well already be above the optimum temperature for your plants to thrive, ideally this should not go above a nominal 25˚C either above the ground level or below it.

If the temperature coming in is already high, you are going to make this problem worse when you start to add the heat of the light, the ballast, the fan and any control gear, all of which make a contribution to raising the temperature.

If the ambient air temperature outside does rise above 25˚C you have the start of a problem. Above 30˚C the oxygen absorbed within the water at the root level will be released and can not naturally be re-absorbed. Oxygen is required by the roots to ensure a healthy plant above ground.

Summer Air Remedies

Locate all ballasts and control gear outside of the grow room area if at all possible. This will reduce the contribution your energy sources have on the ambient temperature of the room.

Extract the air from around the light bulb area using an extracting light shade if possible or have the extraction hose suspended so as to pull air from this area. A 600w light bulb will increase the temperature of the room significantly.

Use a good quality fan speed controller and make sure the fan temperature probe is located near the mid-point of the plant, so you are allowing your extraction and inlet fans to measure the heat of the plants growing environment. You may be able to extent the probe by using 2-pair phone wire available from an electrical retailer.

Use an "in" and an "out" fan, as a rule, the out should be slightly bigger then the in and both should be controlled by a good quality thermostatically activated fan speed controller

Make sure you take clean pre-filtered air from a north facing source to minimize the risk of solar gain on the air temperature.

Ensure any outlet is well away from the inlet point to avoid circular air movement within the room, as this will slowly heat the air above the ambient temperature outside.

Use an air pump on a timer (15mins every 2 hours of light is sufficient) connected to air stones or porous air-hose to get oxygen to the roots, this will ensure that the water around the roots is getting a constant supply of clean fresh air and will re-oxygenate the water if it does get above 30˚C

Use an air pump to constantly aerate your water tank to prevent stagnation.

Use an air-conditioning unit to bring the ambient temperature down, this is not cheap to buy or to run, but it I the only sure way of keeping the temperature down in the growing room.

Insulate the grow room so as to minimize the effect of the external temperature fluctuations, but also to reduce the amount of area you are trying to control.

Winter Too Cold!

As the seasons change the problems you need to consider in the grow room change too. As the air temperature drops, you need to ensure the air is not creating thermal shock for the plant. This can be as big an issue to control as the summer high's, but the equipment used can often be considerably cheaper to purchase if not to run. Avoid letting the temperature drop below 15˚C as this can cause the plants to pause and consider their options, if it happens too often, you may shock the plants in to all sorts of unwanted behavior. Depending on what you are growing you may even find the plant turns hermaphrodite as a result starts to produce male pollinating flowers.

Winter Air Remedies

Draw the air in from the south of any buildings to maximize the benefits of thermal gain.

Use an area between the inlet and the grow room to pre-heat the air to the required temperature.

Reduce the background speed of the fans to their minimum setting to reduce the effect of the ambient temperature.

You may wish to consider placing the outlet fan in to the inlet area, so as to maximize the benefits of the pre-heated air. This can be a difficult technique to control, so should only be used by growers who are comfortable with the dangers and are able to react to the changes our natural environment creates.

 Use a good quality temperature activated fan speed controller.

Use a good quality oil heater rather than a fan heater if possible.

Air Movement

Air movement is required by the plants in order to refresh the air around the leaf and prevent rot and other problems from occurring, however, to much air movement can cause problems with fluid uptake and root v's plant development. Imagine a tree grown on the windward side of a hill compared against one grown on a south facing valley, the one exposed to the wind will have a smaller top and a larger root system than the one grown with plenty of protection and plants are no different.

Keep the air around the leaf moving gently never allow them to move violently or bend in the force of the air movement.

Air Movement Remedies

Net the plants of to ensure they do not collapse as the fruit/crop grows. This should take place as soon as practical so as to minimize damage, but not too low down the plant or the benefits will not be felt later on as the problem will have grown beyond the solution.

Use an oscillating fan to direct air to the lower part of the stems, Correx can be placed around the plants above this area to prevent the air strength becoming a problem to the rest of the plant.

Prevent the air speed causing significant leaf movement as this increases the plants need to uptake water at a greater rate than the nutrient available in the mixture. The effect of this is to gradually increase nutrient strength in the tank. Keep an eye on the CF or EC of the nutrient solution both in the feed tank and in the plant tray as large variation can give clues to oncoming problems.    

Use a good quality fan speed controller and point any inlet away from the plants themselves. It is good practice to point any inlet over the lights to stir up the air there.

Use an "Air-Sock" to distribute the intake air evenly and cleanly (no bugs etc).

Food

 

Most plants require 16 basic nutrients including Iron, Magnesium, Phosphorous, Potassium, Nitrogen, Calcium etc. In addition they also require a vast range of trace elements such as zinc in order to really thrive. How these nutrients are balanced in percentage terms against each other depends on the stage of growth or bloom the plant is in. The plant requires more Nitrogen to grow and more Phosphorous to flower, so your choice of nutrient has a significant impact on the end result.

 

Also, the strength of the nutrient will change over time, getting stronger as the plant develops before reaching a plateau and finally dropping off to nothing at the end of the life cycle. The ability of the plant to uptake nutrients is affected by osmosis, the process of a weak solution drawing a stronger solution through a membrane in the plants root system. If this balance in osmosis is not correct to the stage of the plant, you can actually draw any food out of the plant back in to the nutrient solution and potentially damage or even kill it.

 

Hydroponic systems often replace the growing medium of soil,(which may or may not contain the nutrients you require) with an inert product that can then be added to in a controlled method. As a rule of thumb, the following nutrient solutions are required as a minimum:

         

          Propagation Nutrient – A weak formulation specially designed so as not to damage young plants with delicate root systems

 

          Foliar Feed – To feed young plants and cuttings with no or small root systems. This may be the same product as the Propagation Nutrient above.

 

          Root Enzymes – To eat any dead roots and turn the residual organic matter in to usable nutrient for the pants.

 

          Grow Nutrient – Either A&B or Single Pack, this is high in Nitrogen and therefore promotes strong healthy plants

 

          Growth Stimulant – Normally foliar fed and high in Nitrogen, these products are great at creating many young shoots ready for conversion in to cuttings.

 

          Bloom Nutrient – Either as A&B or Single Pack, this is high in Potassium and Phosphorous and promotes healthy flowering

 

          PK Supplements – Additional Phosphorous (P) and Potassium (K) will benefit the weight and quality of the final yield

 

          Bloom Stimulant/Bloom Boost – required in order open the door in the roots for the PK supplement to walk through, do not use one without the other as you are not likely to get the full benefits of either.

 

          pH up/down – pH stands for Potential Hydrogen and is measured on a scale of 1 to 14, 1 being very acid and 14 very alkaline. The scale is exponential as the magnitude of change up or down the scale changes by a factor of 10 for each increment of 1 along the scale. Therefore, 7 is 10x more acid than 8 and 10 time less acid than 6 on the scale. Plants should be maintained (generally) around the 5 to 7 mark with the ideal being 5.7. However, do not spend too much time worrying about small changes as these will occur naturally as the water reacts with the nutrient which in turn reacts with the root system. Try and maintain an average of 5.7 +/- 0.3 and you should be fine. Use a pH meter to test this or use a simple test solution and litmus paper. If a meter is used, make sure you calibrate it regularly.

 

          Mite control – It is good practice to keep some spider and other mite control substances to hand, many of which are organic in their nature. However, take care what you use on food crops and try and avoid any use at all once flowers have began to develop on food crops as their taste can be tarnished by what you apply. Natural predators are a good alternative to liquid and vapor applications in the later stages of flowering.

 

 

 

NB

CF/EC control – Always follow the nutrient manufacturers guidelines and use a CF (Conductivity Factor) or EC (Electrical Conductivity) meter to confirm you have not made up the solution too strongly. These devices measure the salts that are dissolved within the solution only and will not distinguish between the balance or ratio of one salt over another.

 

Water

 

Water is the basis of two of the raw materials required by the plant, from the water the plant gets it Hydrogen (H) and its Oxygen (O) (see above about the oxygen content and the effect of temperature). If you use tap water, it will have a higher concentration of calcium than  if you use rain water. The type and source of water will also effect the pH reaction you get when you add the nutrient to it.

 

Rain water is more acidic than tap water because tap water ahs normally been filtered through calcified rock such as lime stone, where as the rain water has not undergone this process and will therefore be more acidic. When you add the nutrient (which is naturally acidic) to the tap water you can expect to see the pH rise as the acidic nutrient reacts with the alkaline tap water. Conversely, if rain water is used, the already acid water will be made more acid by the addition of the acidic nutrient.

 

Water from different rivers and reservoirs can be significantly different to each other even within the same geographical regions, so there is no way of giving any useful guide to this problem, use a test meter or litmus paper to test your local water to be sure of your pH requirements and calibrate regularly.

 

The temperature of the water has a significant effect on the plant as if it is too hot the oxygen will be released (stagnated water) and if it is too cold you will shock the roots.

 

Hard or Soft Water

 

Some nutrients come as HW (Hard Water) and SW (Soft Water) variations, this is measured using a CF/EC (one is 10x the other) meter and your fresh water source. Dip the meter in to the fresh water and look at the background CF (dissolved salts) of the fluid.

 

0-3.5 = soft water

3.6+ = hard water

 

Water Remedies

 

Always follow the guidelines of the manufacturer and make sure you pH balance after you have added all nutrients, stimulants and other additives, not before.

 

Use a nutrient heater to maintain the temperature of the main tank in the winter.

 

Use a heated propagator to do the help maintain a steady 20˚C for any cuttings.

 

Prevent over heating the water and if required use a nutrient cooler in the summer months.

 

Use a regionally specific nutrient solution to avoid the need to pH balance the solution, this requires a water sample to be taken, please ask for sample bottle.

 

Use a good quality pH and CF tester at all times and always regularly calibrate.

 

Use a small water pump in the main tank to keep the solution agitated at all times, this will prevent the solution forming in to strings as chemical reactions take place, this is true for all nutrients even if they are organic in their formulation.

 

            Maintain the pH around 5.7, but do not worry about small variations