Electrical conductivity or EC as it relates to hydroponics is a measure of the dissolved salt content in any given aqueous solution.
To put it more simply EC indicates how the strength of any given nutrient mix you have made up. The more nutrient you add to your mix the higher the EC will be.
EC is the primary measurement used in assessing how much nutrient to give a plant at any given point in its life cycle. As plants grow they require more nutrition to stay strong and healthy, young plants will usually require an EC of between 0.2 and 1.0 where as fully mature flowering plants may require an EC of between 2.0 – 3.0.
For horticultural purposes EC is the most accurate way to measure the concentration of nutrients in your mix however there are other units of measurement relating to this, these are Parts Per Million (PPM), Total Dissolved Solid (TDS) and Concentration Factor (CF).
Potential Hydrogen or PH is a measure of how acidic or alkaline any given liquid is.
Understanding and managing the PH of your nutrient mix is extremely important when growing hydroponically. The PH scale ranges from 0 to 14 where 0 is the most acidic, 14 is the most alkaline and 7 is neutral. Pure water has a PH of 7 whereas lemon juice which is acidic has a PH of around 2 and bleach which is alkaline has a PH of 12.
PH becomes important for hydroponic growers when we start thinking about feeding our plants, as we add different nutrients to our water these nutrients will have an effect on the PH of the mix, some nutrients will raise the PH and others will lower it, the key is once we have everything mixed up and we have ensured our EC is correct we then need to check our PH and adjust it if necessary.
PH is easily adjusted by using a ‘PH Up’ or PH Down’ solution sold at all good hydroponics stores. All plants have a preferred PH range that will ensure healthy vigorous growth, most plants like a slightly acidic range of between 5.5 and 6.5. If the PH of your solution falls out of the required range then the plant will be unable to take up and use key elements from the nutrient solution and thus deficiencies or toxicities will soon appear.
There are some very helpful videos online for those growers interested in learning about the chemical processes behind PH and PH changes however provided a grower knows their plants desired PH range and has the ability to measure and adjust the PH of their nutrient solution everything should be AOK.
EC (Electrical conductivity) requirements change as the plant grows from seedling into a mature plant. When your plants are young they require less food, so it makes sense that as the plant grows we increase the amount of food to fulfil the plant’s needs.
Seedling requirements: 0.4 – 0.6
Growth/Vegetative requirements: 0.6 – 1.6 EC
Bloom/Flowering requirements: 1.6 - 2.4 EC
The consensus for pH in a hydroponic system & coco coir is that it should be kept between 5.5 - 6.5 throughout the cycle, ideally in the growth/vegetative phase pH should be maintained at 5.8-6.2 - if the pH fluctuates too much the plant will be unable to uptake specific nutrients, so having the necessary equipment like a pH pen will save a lot of guess work.
When the plants go into the flowering phase consistency is key ensuring the plant has a constant supply of the nutrients it requires, the preferred range in flower is 6.0 - 6.4 as different elements are required in the bloom phase, if this range was lower or higher the plant would be unable to absorb targeted nutrients, thus stifling development and severely impacting the end result.
The general rule of thumb for vegetating plants is 18 hours of light and 6 hours of darkness, once flowering has begun or the plant is of suitable size to flower you will need to change your photoperiod to 12 hours on and 12 hours off, keeping in mind that once your plants start flowering the darkness cannot be interrupted, if light enters the space when flowering, you could reset the plant to vegetate or even worse, they can mutate which will massively impact the end result. It is not recommended that plants receive 24 hours of continuous light at any time during the life cycle. Many growers will leave their lights off for the final 36-48 hours of their grow to great results.
For optimum growth, it is best to maintain your nutrient solution at a temperature of between 18 – 22 degrees (C)
If the room temperature falls below 17 degrees during the dark period, then you will require a water heater. If the nutrient solution does go below 18 the plant can stop growing and go into shock.
If the solution is above 22 for too long it can become the perfect breeding ground for algae, Pythium and a host of other bacterial infections
There can be a number of reasons for this. Firstly, eliminate the obvious things like lack of water, high temperature or a broken stem.
Root diseases are the most common cause of "sudden death" for plants and can cause many problems from loss of yield to complete death. Pythium is the most common disease. Ignoring the basics on temperature control can present quite a nightmare. Always use nutrient conditioners if you reservoir is prone to temperature rises, these formulations mostly contain quaternary ammonium and copper which will help prevent nasty pathogens from taking hold.
This is usually caused by overfeeding i.e. giving your plants too high an EC before they are ready for it. It can also be caused by a buildup of salts/food within your growing medium. If you suspect either of these scenarios it’s a good idea to fully flush your plant then go in with a reduced EC.
There are some nutrient deficiencies that can also cause leaf tip burn. Again, if the gardener has themselves a pH and EC meter this is rarely an issue.
This can be caused by a number of factors:
All of these prevent the plant from absorbing nutrients in the correct quantities, always use an EC meter and a pH pen to prevent this from happening. It should be noted that towards the end of the flowering cycle it is normal for the lower leaves on the plant to start turning yellow.
Plants stretch when their light source is insufficient, humidity is too high or they are crowded by other plants.
Lowering or turning up your light, increasing air flow or spacing plants further apart are some good options.
It should be noted that for 14-21 days after the lights are changed to a 12/12 cycle your plants may ‘stretch’. This is more referring a period of further vigorous vegetative growth and should be anticipated.
Vegetating/growth: 55-65%
Flowering/bloom: 45-55%
Drying: 45-50%
Curing/storing: 55-65%
Excessive humidity for long periods will create undesirable conditions that are perfect for grey mould to thrive. Grey mould, once started, will quickly spread and affect your entire crop.
Using a hygrometer device mounted on the wall inside your hydroponic grow room will let you know at a quick glance what your humidity levels are. Humidity levels of just above 50% during flower is perfect and should not go above this. It is important to keep nutrient reservoirs covered at all times so that they do not contribute to higher humidity levels.
Humidity levels can be easily controlled as with temperature by using inlet & extractor fans to rid the room of heat or humidity. Generally, it is good to keep your grow rooms clean and dry. This will help prevent any mould problems.
While the lights are on temperatures should be maintained between 22 and 28 degrees. When the lights are off temperatures are permitted to drop by 5 degrees or so. It is best to avoid large temperature fluctuations in the growing space at all times. If temperatures fall outside the optimum range for too long development can be significantly stifled or worse. Your main tool for regulating temperature and humidity in the grow room will be a quality exhaust fan.
Plants stretch when their light source is insufficient, humidity is too high or they are crowded by other plants.
Lowering or turning up your light, increasing air flow or spacing plants further apart are some good options.
It should be noted that for 14-21 days after the lights are changed to a 12/12 cycle your plants may ‘stretch’. This is more referring a period of further vigorous vegetative growth and should be anticipated.
