- Benefits to CO2 enrichment:
- nitrogen fixation
- increased stem thickness
- increased leaf area
- increased shoot weight
- increased leaf weight
- increased plant height
- accelerated root growth
- early flowering and fruiting
- increased flower weight
- shorter cropping cycle
- increased water use efficiency
- increased resilience to the stress of pollutants, temperature fluctuation and drought
- The atmosphere has 340 ppm (parts per million) of CO2. That is 0.0036%
- Plants breathe in carbon dioxide and breathe out oxygen
- Plants benefit from CO2 increases up to 2000ppm
- The optimum level of CO2 for most plants is between 800 and 1350 ppm
- 90% of growth increase is obtained with the first 1000 ppm of CO2 in the atmosphere
- One cubic metre at 1000 ppm contains one litre of CO2
- Every cubic metre must have between half and one litre of CO2 added to optimise CO2 level
- If you add one litre of gas to a cubic metre of air, the CO2 level will be (1000 + 340) = 1340 ppm
- Optimal temperature is 21 to 27 degrees
- Growth rate slows markedly if the ambient temperature rises above 35 degrees or falls below 21 degrees
- When the temperature reaches 35 degrees, the benefits of CO2 enrichment become zero
- Excessive heat reduces the ability of the plants to absorb CO2
- The only air conditioner suitable is a refrigerant one. Set to recycle, not draw in from outside. An evaporative air conditioner will absorb CO2 from the air, wasting it
- Levels above 2000 ppm are detrimental and become toxic to plants
- Work-safe recommends humans are not exposed to 5000 ppm (averaged) over an eight hour period. Plants begin to die at this level
- Properly seal room (especially around the extraction fan) so CO2 won’t escape through leakage
- Set your CO2 unit to come on before the light switches on and to turn off just as the light switches on. When the light comes on, the room will contain optimum CO2 in the air that the plants can use immediately
- Place your CO2 unit on a shelf, desk, cupboard etc. Never sit your unit on the floor
in hydroponics, plants uptake nutrients that are dissolved in water rather than nutrients available in soil. Most of the time, these nutrients are provided to the plant in an ionic or inorganic form. In order to grow healthy hydroponic crops, it is essential that growers maintain proper electrical conductivity (EC) and pH levels.
For most hydroponic crops, the ideal range of EC for most crops is between 1.5 and 2.5 dS/m. A higher EC could prevent the plant from absorbing nutrients due to increased (more negative) osmotic pressure, and EC levels that are too low could adversely impact yield.
What is EC?
In hydroponics, electrical conductivity (EC) is a measure of how easily electricity can pass through your nutrient solution. Similarly, the conductivity factor (CF) is a measure of EC with units of millisiemens per centimeter (mS/cm).
Most plant nutrients are available as soluble ionic compounds. Ions are charged particles. Adding more of these charged particles will increase the EC of a nutrient solution.
Units of EC
In order to be able to read and interpret EC readings taken from your nutrient solution, it is important to understand the units used to measure EC.
EC is typically expressed as siemens per unit area (e.g., mS/cm, dS/m, S/m). For a nutrient with a conductivity of one S/m, the electric current through a nutrient solution will increase by one ampere for every increase of one volt of electric potential across one meter of solution.
Various metric prefixes are used when expressing EC readings. The table below lists some of the common prefixes used for EC.
Converting EC to ppm
As previously discussed, EC is a direct measurement of the electric conductivity of a substance. Because the nutrients dissolved in the water used for hydroponics are ions, EC can also be used as an indirect measurement of total dissolved solids (TDS). TDS is measured in parts per millions (ppm) and represents the concentration of nutrients in the solution.
EC Ranges By Hydroponic Crop
Not every plant has the same optimum EC value. There are a number of reasons for this. First, different plant species have different nutritional needs. The amount of nutrients in the nutrient solution impacts EC levels.
The optimal EC also depends on the plants’ stage of growth. Seedlings prefer nutrient solutions with a lower concentration of nutrients (lower EC) because they can burn easily. In contrast, more mature plants should be grown in nutrient solution with a higher EC.
In addition, environmental factors such as the ambient air temperature are important in determining the optimum EC. For example, when the ambient air temperature is above 86°F (30°C), EC levels should be reduced to account for the reduction in the plant’s rate of photosynthesis.
The optimum range of EC values for different hydroponic crops is listed in the following table.
|1.4 to 1.8
|1.2 to 1.5
|1.0 to 1.6
|2.0 to 4.0
|1.8 to 2.2
|2.8 to 3.5
|2.5 to 3.0
|1.8 to 2.4
|2.0 to 3.5
|1.7 to 2.0
|2.5 to 3.5
|1.6 to 2.4
|1.4 to 1.8
|1.2 to 1.8
|1.5 to 2.0
|0.8 to 1.8
|1.8 to 2.2
|1.6 to 2.0
|1.5 to 2.5
|1.0 to 1.6
|1.8 to 2.3
|1.8 to 2.2
|2.0 to 4.0
|1.8 to 2.4
The Impact of EC On Plant Yield
So what is the impact of growing plants in a nutrient solution with EC levels that are above or below the optimum range?
A research study that examined the effects of EC on tomato yield found that yield increased as the EC of the nutrient solution increased from 0 to 3 However, the yield decreased when the EC was further increased from 3 to 5 . Researchers found that EC levels between 1 and 3 , depending on the stage of growth, resulted in higher tomato yields.
Symptoms of Excessive EC
Ironically, signs of excess nutrients are similar to the symptoms of nutrient deficiencies in conventional growing systems. For example, excess magnesium in a hydroponic system looks just like calcium/magnesium deficiencies in growing media.
In general, here are some signs that the EC of your nutrient solution is too high.
- Leaf and stem wilting
- Tip burn
- Stunted growth
- Dropping leaves
Note that many of these symptoms may also indicate other problems such as disease, lack of water, too much heat, or excessive light.
If you suspect that the EC of your nutrient solution is too high, dilute it with distilled water. As you are adding distilled water, take measurements intermittently until the EC is back to appropriate levels.
The average daily water loss in a hydroponics system ranges from 5% to 30% depending on the size of the system and the type of plants you are growing (. This water loss results in a nutrient solution with a high EC. This means you should be measuring the EC of your system on a regular basis.
There are a variety of EC meters available at different price ranges. So what should you look for when searching for an EC meter? Depending on your budget, you will want an EC meter that is waterproof, has a battery life indicator, is easy to use, has an automatic shutoff, is shockproof and is easy to calibrate.
The most popular brands of EC meters are Bluelab, Hanna & Essentials,. starting at $180
Keep in mind that cheap TDS meters tend to be less accurate than some of the more expensive EC meters. starting at $50
Larger grow rooms require higher-quality EC meters. An example of such meter is the Bluelab BLU27100 Guardian Monitor. This monitor costs between $550 and $650 and has alarms that alert you if your EC gets too high or too low.
Calibration and Cleaning EC Meters
If you consistently use your EC meter, salts will build up on the meter. This salt buildup can skew your readings and shorten the life of the EC meter. For this reason, it is important to calibrate your EC meter before taking readings. You should also clean your meter after every us
You can hardly wait to get started with your hydroponic system. You’ve researched light, spacing, and nutrient requirements for your plants. Don’t forget one of the most important factors in hydroponics: pH levels. If the pH level is too high or too low, plants cannot absorb nutrients and will not thrive in otherwise ideal conditions. Read on to learn the role of pH in hydroponic systems and how to properly monitor and maintain its levels.
A pH test shows whether a substance is acidic or alkaline. The pH scale ranges from 0 to 14, with 0 being the most acidic, 14 the most alkaline, and 7 is the pH-neutral point. Some plants prefer acidic conditions while others require an alkaline environment. There are many methods available for testing and adjusting pH levels in hydroponic systems.
Why pH is Important in Hydroponic Systems
The right pH level is crucial because it affects nutrient availability for your growing plants. A pH level that is too high or alkaline can prevent nutrient uptake and lead to deficiencies. Iron deficiency causes pale or yellow leaves in young plants, while leaf cupping and tip burn are telltale signs of calcium deficiency. Calcium can also form salts that leave white deposits or scale on reservoir walls and equipment.
Hydroponically grown plants need different pH levels than plants grown in soil. Without soil, plants do not benefit from microorganisms, organic matter, and interactions between water and minerals that regulate pH levels. The hydroponic gardener must constantly monitor and adjust pH levels. Make sure that you do not apply pH recommendations for soil-grown plants to hydroponically grown plants.
Typical pH Ranges for Crops
With some exceptions, the optimal pH range for hydroponically grown crops is generally between 5.5 and 6. Many fruits and vegetables, such as melons, apples, beans, squash, and tomatoes prefer that range. Blueberries, on the other hand, need a lower, more acidic pH between 4.0 and 5.0. It’s a good idea to use separate nutrient reservoirs for plants with similar pH ranges.
Some hydroponic crops have a wide optimal pH range. Pumpkin, for example, will thrive in a pH between 5.5 and 7.5. Crops that require alkaline conditions include kale, onions, and peas, which prefer pH levels between 6.0 and 7. Mint plants tip the scale at an optimal pH range of 7.0 to 8.0.
Typical pH Ranges for Nutrient Systems
Hydroponic nutrient products typically start with pH levels between 5.5 and 6.0, the optimal level for most crops. The pH range, however, depends on the specific formulation. For example, ammonium nitrate has a more acidifying effect than nitrate and will cause a drop in pH. Calcium salts, on the other hand, cause a rise in pH, resulting in a more alkaline solution.
Specific nutrients require certain pH levels for plant uptake. The wrong pH level can result in too little or too much of certain nutrients. For example, when the pH level drops below 5.0, plants can develop magnesium and calcium deficiencies or copper and iron toxicity. A pH level above 6 or 6.5, however, can cause iron deficiency.
Why pH Levels Change in Hydroponics Systems
Several factors can cause pH levels to change in hydroponic systems. When the amount of the nutrient solution drops below one gallon, the solution becomes more concentrated as plants absorb the nutrients. This results in widely fluctuating pH levels. It is, therefore, important to monitor nutrient solution levels, keep the reservoir full, and regularly test the pH in the reservoir.
Both inorganic and organic matter can affect pH levels in hydroponics systems. For example, gravel and other inorganic growing media act as a buffer and cause pH levels to rise in media-based systems. In a natural environment, soil acts as a buffer in a similar way. To get an accurate pH reading in a media-based system, test the pH of the reservoir solution as well as the solution (leachate) that drains from the beds or bags that hold the plants.
Algae and bacteria are the main types of organic matter that affect pH levels. If pH levels rise in the morning and drop later in the day, algae may be the culprit. As algae consume acidic carbon dioxide during the day, pH levels rise and then fall by evening. On the other hand, bacteria from root disease can cause a dramatic drop in pH levels. As diseased roots decompose, bacteria will release acids into the hydroponic solution.
How to Maintain the Right pH Levels
The first step in maintaining the right pH levels is testing. A variety of testing supplies are available. Test strips and liquid test kits are the least expensive and are available at pool supply stores and garden centers. Digital pH meters are more accurate and offer repeatable results. You should test frequently with whatever hydroponic testing instruments you choose, even daily if you have recently adjusted nutrient levels or have little experience with hydroponics.
If you use a recirculating system, adjust the pH level according to test results from the supply reservoir. In a media-based system, however, the pH changes as the nutrient solution travels from the supply reservoir and out through the grow base. Adjust pH levels based on the pH of the leachate that drains from the grow beds.
Commercially prepared “pH up” and “pH down” products are available to maintain the right pH levels. You can purchase these products in dry or liquid form and use them according to label instructions. Make sure you use products that are formulated for hydroponic systems. For small systems or short-term results, you can add weak acids such as vinegar or citric acid.
Automatic pH controllers cost more than pH up or pH down products but they keep the pH at consistent levels. This option works best in recirculating systems to prevent pH fluctuations that occur as plants feed.
If your water is hard, the buffering effect of the high mineral levels will cause high pH levels. A reverse osmosis system is an efficient and relatively affordable method for reducing water hardness.
Benefits of Measuring and Maintaining pH Levels
Each plant needs certain growing conditions to thrive. It’s worth the time and effort to monitor and adjust pH levels in hydroponic systems. If you know the optimal pH ranges for your plants, you can take the necessary steps to keep your hydroponically-grown plants healthy.
FLOOD & DRAIN
The Flood and Drain System is an excellent growing system suitable for many types of plants from fast growing vegetable crops – long term flower crops.
So how does the Flood and Drain system work?
It operates with an irrigation system that floods the grow tray with nutrient solution from the reservoir hidden underneath. The nutrient solution floods the tray for a short period of time then drains back to the reservoir.
The benefit to this system is that it can work off a timer. Set and forget!
What’s the best medium to use?
There are many types of medium that work well with the Flood and Drain
- Clay Balls
- Perlite or Perlite / Vermiculite mix
Clay balls can be used straight into the tray and used as a garden bed or you may choose to plant in pots and use the clay balls as the grow medium. Clay balls allow for excellent aeration of the plant roots.
If choosing to use Perlite its best to plant in pots.
Flood and Drain Kit Comes complete with :
- Grow tray (Various sizes avail, 1050 x 1050 most common)
- Aluminum Stand
- Irrigation fittings / plumbing
- 68 Litre reservoir
- Water pump
- 24 hr Timer
- Clay balls
- Nutriflo Grow Nutrient
NB : You can expand your Flood and Drain System and have 2 or 3 grow trays connected to the existing reservoir and pump.