This thread has become so repetitive. To each his own, you can do whatever you like. Please stop presenting anectodal reports as scientific facts, they barely constitute as “data” and please don’t defend mistakes by giving examples of other mistakes. Thats is just sad.
I’ll write this one more time for my benefit. Flushing is the name, given to a process which involves running copious amounts of water thru the medium. Just like flushing a toilet. The expected effect is to strip free ions from the mix. This can be achived. I’m not opposing to this. I’m opposing to the practise of overfertilizing and then expecting that running X times of water will make everything allright.
First of all, when you saturate the mix with fertilizers, those ions bond with the medium itself. The cations that is. The cations, which are the positively charged ions, bond with the medium, which is negatively charged. The negatively charged anions however, is being repelled by the medium itself and phosphate is just so reactive that it bonds with everything and becomes unsoluble.
Now for the purpose of stripping anions, running copious amounts of water can be used and in the process some percentage of cations will be stripped too and will be replaced by hydrogen ions or any other positively charged ions. But this is not a big percentage, its just not feasible. Also should i mention most of the plant fertilizers are made up of cations for this reason. So that they cannot be stripped easily with water.
The base saturation of a mix is made up of cations that have created a bond with the medium and also with the organic material in the mix, that are needed for growth by the plant. At lower ph levels, the base saturation will also decrease by percentage because mostly aluminium and hydrogen ions will be there readily bind with the mix. We usually go with 6.5-7.0 ph levels. Now this is not acidic so the base saturation would be high. That means, most of the ions that medium is holding, is in fact nutrient ions with a positive charge like calcium, magnesium, potasium etc. Most of these are there to stay with strong ionic bonds.
There is also a special kind of cations called exchangeable cations. These are cations that have bonded with the medium with a weak ionic bond, that keeps them there but plant can trade in hydrogen ions to strip them from the soil.
This high CEC is what keeps humus and any organically rich soil, fertile and rich in nutrients. These types of soils are found in the most humid environments like forests, marshes etc. They’re under constant moisture and rain.
If one needs or wants to strip the medium of all nutrients. Using only water for this process is wasteful imo. The natural leaching of elements from the soil is a real concern. Outside, the rain strips ions from the soil and leaches them deeper and deeper into the soil. So by that logic, its understandable to think that water itself is pretty effective at this stripping action. The overlooked part is outside, most soils have between 10 to 40 CEC value while peat has as high as 200 and rain is actually acidic in most occasions. The water forms carbonic acid with co2 and this process releases hydrogen ions. If you want a true flushing of the medium you will need to use an ionic solution that could replace these exchangeable cations with hydrogen ions for example. The soils ph will decrease too.
These data influences my decisions and views.
As far as going only water at the last 2 weeks. Thats just to let the plant strip whatever is left in the mix and take no more. Everything you see when you look at a plant was once ions. Thats life. It takes up these ions and turns it into cells and resin and chloropyll and million other things. Since cannabis is not a very picky eater, its better to provide only as needed and let it complete its lifespan on a limited diet. Especially if you’re growing for medicinal use and not really fixated on the yields but favor quality instead.
Lets look at the fading and deficiency. I don’t know why this causes such a controversy. Don’t really know why you guys are having hard time understanding me but deficiency is when a plant wants to eat but the medium can’t provide, either because of growers error or by choice.
Senescence or fading is when plant starts to shut down. Literally, it gets ready for dying. This has no direct correlation with flushing, its a plant response but it can be induced prematurely by flushing, creating deficiencies, stressing the plant, like water stress or photoperiod stress or nutrient stress. Or it will happen naturally on its own at the end of its life cycle. All my remarks are concerned with the natural route. When plant slows down its metabolism, there is no need to keep pumping nutrients in, whatevers left in the medium should be more than enough for 1-2 weeks.
Maybe i should make it clear, it should be clear already but seems not, i don’t think you should grow deficient plants. That fading at the end is just letting it die by not providing a life support for it. Thats all. You can keep them going a bit more and get a bit much but you’ll be pumping nutrients in a nearly done plant, and since these are medicinal plants, i wouldn’t want to smoke that.
To sum up, i don’t think we should call the last 2 weeks flushing as we’re not flushing anything, this is just a personal preference. I don’t think real flushing is a good practise unless done right after an overfertilization with nitrate maybe. The difference between deficiency and senescence should be clear to all at this point, seems not. I can truly tell the difference with a faded plant and a green one while vaping. Only true flushing, is not overfeeding at the first place.
I’m done with this thread. Unwatched and everything. To each his own. By the way, i wouldn’t actually take this research too seriously, seeing much of the data and the methodology has been found faulty.
Bountiful harvests to all.
