In general, plants respond best when grow-room air temperatures are maintained in a range of 75 – 82F during the light cycle, followed by about a 15 degree drop in temperature during the dark cycle. Additionally, to ensure replenishment of carbon dioxide being consumed by the garden, and to moderate humidity levels, a fresh air ventilation system should be rapidly replacing total air volume. A healthy humidity level ranges from about 45 – 55%. Levels higher than these create an atmosphere conducive to the growth of harmful fungus/powdery mildew.
To accelerate the process of photosynthesis, and hence achieve accelerated growth rates and exceptional yields, some growers opt to create an artificially enriched CO2 environment by introducing compressed CO2. But in order to realize the full benefits, the grow-room should be sealed to consistently maintain in excess of 1,000 PPM of CO2 in the atmosphere, and equipped with air-conditioning and dehumidifier systems
to sufficiently compensate for the lack of fresh air ventilation. In the absence of this costly equipment, CO2 enrichment can still be effective with a fresh air ventilation system. However, grow-room ventilation must be suspended at regular intervals while CO2 is being introduced into the atmosphere to allow for maximum plant absorption via leaf respiration.
So in simple terms, the message is that your high-value garden will flourish in an environment of moderate temperature with gentle/breezy air movement that’s rich in carbon dioxide content. In summary, keep in mind that each grow-room has its own set of environmental variables, making definitive instructions problematic. But for the most part, grow-room conditions within these “Gardening Guidance” parameters will allow plants to efficiently utilize nutrients and optimally conduct photosynthesis.
Light & Dark Cycles
Regular replacement of lamps (at least once every 6- 8 months, or after every third crop cycle) will ensure that your plants are receiving full light intensity and photosynthetic spectrum. HID lamps mimic sunlight by means of an internal chemical reaction and thus slowly deteriorate during use. Therefore, periodic bulb replacement is a must for a garden to thrive.
In vegetative/growth stages plants ideally want to receive 18 hours of light and 6 hours of darkness. In blooming/flowering stages plants should receive 12 hours of darkness and 12 hours of light. Adhering to these cycles is very important as it allows plants to photosynthesize (produce chemical energy) and respire (expel oxygen and water vapor) during the light cycle, and to curtail the rate of respiration and grow during a cooler dark cycle. Put another way, in order for optimum growth to occur, the products of photosynthesis must be greater than the by-products expelled during respiration; thus the importance of scheduling the proper duration for each cycle.
With the onset of darkness, photosynthesis ceases, respiration slows and plants are stimulated into converting the glucose (chemical energy) created by photosynthesis during the light cycle into more complex sugars and carbohydrates which then become the fuel for plant growth.
A complete plant nutrition program must comprise the correct amounts of the macro nutrients: nitrogen, phosphorus, potassium, calcium, magnesium and sulfur; in combination with micro nutrients (trace elements), which usually consist of: boron, chlorine, copper, iron, manganese, molybdenum, and zinc. Significantly, even though micro nutrients are required in much smaller quantities than macro nutrients, they are no less important to plant function and development.
The synthetic/chemical forms of these nutrients promote rapid plant growth and flowering; whereas organic/natural fertilizers enhance growth over time, but also produce a superior aroma and flavor in fruits and flowers.
Synthetic fertilizers are inherently potent; so there’s a need for caution to avoid over-fertilizing and nutrient burn. Thus, many professional gardeners employ nutrient additives which contain combinations of both chemical and organic ingredients in order to utilize the advantages of each and safely boost reservoir nutrient levels. Additives containing humic acids, sea weed, exotic plant extracts, bat guano and earthworm castings are among the most beneficial.
Water & pH
Pure water displays a neutral pH of 7.0. However, for optimum nutrient uptake to be achieved, the pH must be lowered to a range of about 5.6 – 6.2 It is only within this range that hydroponic root systems can properly absorb and process available nutrients efficiently. It is also vitally important for reservoir temperatures to be maintained in a range of 65 – 70 F, and be well aerated by employing multiple air-stones. These conditions allow the water to retain healthy levels of oxygen, while also ensuring nutrient uptake by the roots. These temperature and pH parameters should also be observed when foliar spraying.
In addition, it is highly advisable to treat tap water by means of a reverse osmosis filtration system. This removes undesirable mineral salts leaving behind pure, salt free water. The use of RO water is advisable for achieving consistently robust yields in hydroponic gardens. The major advantage of removing the existing salts from your hydroponic water supply is that it ensures your plants are getting only beneficial salts. That is, healthful nutrient salts which are specifically blended for plant nutrition.
PPM / EC (electrical conductivity)
Put simply, PPM/EC gauges how an electrical current moves in the nutrient solution. Synthetic fertilizer salts ionize when added to a hydroponic reservoir and thus raise the level of electrical conductivity. This is why a rising PPM value indicates an increase in nutrient concentration. When a nutrient solution becomes excessively concentrated, plant roots can suffer from chemical salt burn. Further, once the uptake of the overly-concentrated solution enters a plants vascular system it often results in salt-stress and nutrient burn in the leaves. Ironically, the end result is a plant that appears to be suffering from nutrient deficiency!
Alternatively, organic fertilizers contain a relatively low salt content with correspondingly low EC values, which makes them safe for use as additives to an already potent synthetic base-nutrient mix.
Root Zone Health
It should be emphasized that good plant health begins at the roots. And good root heath depends in large part upon generous concentrations of oxygen at the root zone. Among the easiest and most efficient methods to ensure a healthy root-zone are to equip the reservoir with multiple air- stones for delivering thorough aeration, and the introduction of friendly bacteria into the nutrient mix. The application of mycorrhizae powder and
enzymes are an effective way to accomplish this. And not to be overlooked is that for healthy oxygen levels to exist, moisture must always be present in the grow media/root zone, but never saturated for extended periods. The beneficial results of these simple procedures should be manifest in healthy white root coloration and an abundance of fine root hairs. And in addition to optimizing nutrient uptake and thus increasing the overall vigor of plants and their root systems, these measures greatly reduce the occurrence of waterborne fungal diseases like pythium.
Of high importance to hydroponic gardeners is to understand that excessive water temperatures will reduce available oxygen to the root zone. The lack of oxygen in turn can damage the root system, which in turn affects the plant’s ability to uptake nutrition.
Other causes for lack of root-zone oxygen can be the decomposition of dead organic material in the Rhizosphere. Another common issue is too many plants competing for a limited oxygen supply. However, oxygen starvation as a result of excessively warm water is the foremost cause of root-rot in hydroponic systems. This is because nutrient uptake is an active process that relies on several factors to function properly; one of which is that adequate levels of oxygen must be available to facilitate root function. One aspect of this function enables roots to draw dissolved nutrients through their permeable exterior to their interior where these nutrients then make their way into the plants vascular system and are transported to the leaves.
This water/nutrient pumping process requires energy. To provide this energy, a percentage of the glucose produced by leaf chlorophyll through photosynthesis is transported to the roots and becomes fuel for the nutrient pumps. However, unlike the manufactured glucose, oxygen is not transported from the leaves to the roots. Therefore roots must obtain oxygen from moisture in the root zone. If the roots cannot obtain sufficient amounts of oxygen because of excessively warm nutrient solution, or because there isn’t enough air space in the growing medium, their pumping capacity is significantly reduced. The inevitable result is that the plant becomes dehydrated and nutrient starved.
Coco, rockwool and clay pebbles are popular examples of inert media used in hydroponics. Inert means that these media contain no usable bio-materials or nutrients for your plants. The only role these media play is in providing a strong substrate in which roots can thrive and expand. These media work well for hydroponic gardens because they effectively retain water and have excellent oxygen to water ratios. However, all the nutrient needs of the plant must be supplied by a closely monitored and complete nutrient mix contained in a reservoir.
In contrast, soil based media are alive and biologically active. Micro- organisms can flourish in soil, continually breaking down organic material into smaller particles which can be absorbed as food by plants. High porosity soil-less mixes are made using coco and peat as a base. These mixes of vermiculite, perlite, coco and peat share qualities of inert media, such as air flow and structure, with the added benefits of colonizing beneficial micro-organisms.
In a healthy garden, a symbiotic relationship develops between living,active microbes and fungi in the Rhizosphere; and roots themselves. Beneficial microbes (bacteria and fungi) are essential for decomposing organic material and transforming dead organic matter into readily available and usable plant food.
Beneficial bacteria and fungi form relationships with plant roots to conduct an important exchange which nourishes both the roots and the microbes. A healthy microbial community is essential to plants because they make nutrients in the soil more available for roots to absorb and utilize. Microbes live off sugars obtained from roots, and in turn break soil nutrients into smaller more usable constituents. This symbiotic exchange greatly increases the percentage of nutrient availability to plants. An unimpeded flow of nutrients in turn supports all of a plant’s biological processes and produces healthier plants and more fruit. Abundant nutrient availability causes the plant’s vascular system to produce a higher sugar content, which is directly reflected in the quality of fruits and flowers.
Additionally, microbes will defend plant root systems from invading pathogens and prevent or defeat pests and disease using a variety of natural mechanisms.
As it applies to indoor gardening, hydroponic gardeners using rockwool or other inert media are less reliant on microbial activity and more dependent on soluble fertilizers in the reservoir. Nevertheless, using refined liquid organic additives in conjunction with biological inoculants as part of a nutrient feeding program is the preferred method among many expert hydroponic growers.
Because coco is fibrous and specialty soil-less media are highly porous, these substrate types possess characteristics of both inert and biologically active media, and can therefore effectively colonize beneficial bacteria and fungi. In contrast, purely inert media like rockwool do not readily support this biological activity without the regular addition of mycorrhizae powder to the media / reservoir.
Pests & Fungi
Being proactive by closely monitoring for pests is the best way to prevent crop damage. And while you can’t always keep pests out of your grow room, you can keep your plants protected from major damage. The first step is to agitate your plants regularly to see if any flying pests (white fly, scarid fly, etc.) are present. Look under leaves for tell-tale signs of pests such as spider mites which leave behind tiny black dots. Many different sprays and pest-predators are available on the market to eliminate or control pest numbers.
Using a silica product during grow and bloom also offers pest protection by increasing plant resistance. Additionally, nutrient residue left behind by foliar spraying can act as a deterrent to pests. As for disease, good air circulation and reasonable humidity levels are the best way to avoid molds and fungal disease in the leaf material. Spraying with a preventative anti-fungicide periodically is also a sound practice. Waterborne fungal diseases (pythium, etc.) can usually be prevented with either sterilization or the introduction of friendly bacteria into your nutrient system.
Monitoring Plant Health
Since plants are living and breathing life forms, close attention should be given to their well-being. Regular visual inspection of your plants is extremely important. Monitoring for signs of yellowing, drooping and curling leaves can enable you to be proactive in correcting certain deficiencies in the plant’s nutrition, or in the growing environment itself. Be watchful for mold and pests such as gnats and spider mites as they must be addressed immediately to prevent devastating proliferation.
Too little water and plants will suffer from dehydration; too much water can result in root-rot. Therefore, moisture should be maintained in the root zone, but never saturated for extended periods.
Make sure that your plant is not being over or under fertilized. Over fertilization can cause “nutrient burn”, resulting in dried leaf tips and leaf curling, while under fertilization will appear as general stunted growth and small flowering sites, and may also share some symptoms of over-fertilizing.
Always keep in mind that a garden is a complicated environment where problematic imbalances can occur at any time. So when problems do arise, seek the advice of experienced growers at your local horticulture store and consult the free online education resources on the internet.