Now.. this is not my work. It is the work of woodyJ from the dark side.
I remember the thread as it helped me alot with dwc. Gave me a better understanding of what the readings ment..
So here we go...
This table is not meant to be exhaustive. It is primarily for use in conjunction with DWC & variants or any other hydro setup where you have an air stone. The main complication is the acid rain effect in Note 1 below. This does not apply to waterfall effect or flooming for introducing Dissolved Oxygen.
Its intention is to give anyone suffering ph, EC issues in DWC and variants some idea of the different solutions to the various states you can have.
There are 18 different states you can get in DWC and though many have common solutions, such as a falling EC, which is usually a good sign could mean a slight raise in EC may be needed. However, this depends on the state of the other elements. For example, if our falling EC is accompanied by a falling ph too, this suggests a res change due to either acidic nutrients or ph- or the acid rain effect (note 1) causing the ph to drop.
The first thing to check in any of these scenario's is the meters being used.
Make sure they are calibrated. If you can, check the readings against a second meter if things dont improve after making changes.
As a general guide, if the ph is between 5.8 and 6.2, do not rush into changing anything unless your plants are displaying symptoms of a problem.
In DWC, a good safe EC is around 1.2 to 1.4, I have rarely seen problems with plants fed at this level.
These levels are for healthy maturing plants either just before placing in flower or once into flower. For smaller/younger plants adjust EC accordingly, starting down at around 0.4
This is exclusive of any background EC. So if your source water has an EC of something like 0.5, work with an EC of 1.7 overall. As always, use judgement in finding the correct EC for your plants. This will vary by plant depending on the stage of growth. DO NOT jump in with seedlings of freshly rooted clones with an EC of 1.7, you will kill your plants.
I am also assuming grow media have been washed/rinsed/buffered properly in ph'd water.
Most media (inert) should be soaked in water with a ph of around 5.8 for 24 hours. This tends to help prevent later ph fluctuations.
Water level EC pH Solution
Static Static Static Plant not feeding/drinking, change EC, check meters. Usually, lowering the EC a little should get the plant feeding again
Static Static Rising Ph buffers probably raising ph. This is usual. Having a static water level is not though, so again, a slight reduction in EC or a res change should resolve this.
Static Static Falling Usual cause of this is when media has been rinsed at a lower ph than you require.
The other possibility is that too much CO2 has been pumped into the water. See Note 1.
Change your res and look at the volume of air pumped plus look at your air source.
Static Rising Static Plant is leeching nutrition, raise EC. Note 2
Static Rising Rising Plant leeching nutrition, Raise EC. An unusual state. The rising ph is probably caused by what nutrient leeching back.
If these are alkaline, it will lead to the rise in ph. Could also be ph buffers.
Static Rising Falling As above but be aware of the acid rain effect mentioned in note 1. Res change, plus increase in EC.
Static Falling Static Plant eating but not drinking. Not ideal. Lower EC or res change
Static Falling Rising As above but rising ph is a better sign. Lower EC slightly or res change.
Static Falling Falling Falling ph along with falling EC but no drop in water level suggests a res change. Could also be an acid rain effect as per note 1. Depending on other symptoms, lowering EC after res change.
Falling Static Static Perfect conditions. EC and ph are at the correct level.
Falling Static Rising Normal state most people encounter. Nothing to worry about, carry on doing what you are doing unless other plant symptoms.
Falling Static Falling Res change plus a change of EC. Lower EC if over 1.4, raise EC if lower than 1.0
Falling Rising Static Plant is drinking more than eating, lower EC.
Falling Rising Rising Plant is drinking more than eating, lower EC
Falling Rising Falling Plant is drinking more than eating, lower EC. Also, res change due to possible acid rain problem.
Falling Falling Static Hungry plant, raise EC. Very good situation to be in. Nute buffers are working and plant is taking a balance of nutrients.
Falling Falling Rising Almost as above, usually considered almost perfect, raise EC slightly.
Falling Falling Falling Res change. Potential acid rain issue but plant is still eating & drinking. Raise EC on new res.
The ideal scenario you are looking to achieve is where the EC is either dropping slightly or remaining static, with a static or slightly rising ph and a dropping water level. If you get this situation, keep doing exactly what you are doing because your plant is feeding and drinking.
Even a moderate plant that will be yielding 3 or 4 oz should be going through 3 or 4 l of water per day. I have seen me giving larger plants as much as 10l per day food & water, its like keeping a horse! But you cant smoke a horse
Note 1.
When pumping air into a nutrient solution in order to add Dissolved Oxygen, not only oxygen is present, CO2 is also pumped in. If you live near a busy road, this may be higher than normal, so you may get a dropping ph quite often. I have noticed most of the growers who suffer from a falling ph in DWC tend to live in large cities. This may not be a link but it could be.
When CO2 is added to water, it makes it more acidic. This is the precise process which causes acid rain, pollution from power stations etc pouring CO2 into the air, this mixes with the water vapour in clouds causing acid rain.
Note 2.
Most people assume that with a rising EC, it is the plants way of saying, I dont want more food, here, have some back.
What is actually happening is this.
Plants roots take in water/nutrients through a process called Osmosis. Effectively, if you think in terms of the roots having their own internal EC.
The osmosis process will always try to balance out the EC's, taking from the higher side of the barrier and giving to the lower part.
So if the EC of the nutrient solution is higher than the "internal EC", then food & water will flow from the solution to the roots, this is the normal process.
If however, the EC of the solution is higher than the "internal EC", then the balancing will work the other way and nutrition will be leeched from the roots to the solution.
A res change or increase in EC should resolve depending on the other factors such as ph and water levels.
Note 3.
Nutrients flow around a well hydrated plant much more effectively and faster than one which isnt as well hydrated.
How can growers use this?
By feeding at lower levels, the plant needs to take on more water in order to get the nutrition it requires.
So by feeding at moderate levels, this forces the plant to drink more.
By drinking more, it is better hydrated, because it is better hydrated, it needs more food, making it eat more.
So feed at moderate levels rather than overly aggressive levels.
The method of pushing the EC until you see signs of nute burn is damaging to the plants and although many growers use this method, I am not a fan though your plants are not mine!
If you disagree with stuff in this post, please PM me. I do not want this thread to end up as a big debate or argument. I am hoping people take it as an honest attempt to help those suffering issues in DWC. The info in this post is my opinion. Before taking any corrective action based on this post, please double check.
Hi, I have made a mistake on the note 2 section. Where it reads
"If however, the EC of the solution is higher than the "internal EC", then the balancing will work the other way and nutrition will be leeched from the roots to the solution. "
2 lines from the end of note 2, it should read
"If however, the EC of the solution is lower than the "internal EC", then the balancing will work the other way and nutrition will be leeched from the roots to the solution. "
Sorry for any confusion this may cause.
Thanks to Friday for spotting it.
I hope there are not many more lol.
Thanks to all for the thanks. I had promised to write this up after a couple of guys had issues of falling ph. I hope this explains why and how to solve.
Stay safe guys.
W
