An In-Depth Look at Flushing and Why it Likely DOES Have an Effect on Finished Bud Quality

To flush or not to flush?


  • Total voters
    11

cannetix Inc

Well-Known Member
"Flushing", although a common practice amongst Cannabis growers, is one with a limited amount of information. Although most growers cannot explain the science behind the flushing process, many swear by it from experience, claiming it leads to buds that burn "cleaner" and with better flavor.

Studies show that when excess nitrates are present in the soil, higher plants (including herbaceous plants such as Cannabis) accumulate nitrate, storing it in organelles called vacuoles where it may exist in concentrations as high as 100 mM. In order for plants to mobilize this stored Nitrate, Nitrate supply must drop below nitrate demand. Phosphorus is mainly used by plants for the synthesis of lipids, and it is in these lipids where the plant stores the majority of its phosphorus content. Unlike Nitrogen/Nitrate, Potassium deficiency results in the degradation of lipids and the mobilization of phosphorous through the break-down of phospholipids. These lipids are primarily found in chloroplast membranes and consist of glycerol to which is attached one or two sugar molecules and two fatty acids. The process of breaking down phospholipids to mobilize phosphorus during phosphate starvation is referred to as Membrane Lipid Remodeling. One effect of Membrane Lipid Remodeling is that it causes the cells to disintegrate, causing the content of the cells (including nitrate) to be made accessible for further mobilization. One made available, Nitrates can undergo nitrosation reactions with Alkaloids present in the Cannabis plant (Similar reactions occur in Tobacco primarily during the air-curing process). Due to the fact that unpollinated Cannabis is much higher in lipid-containing oils that would normally be used for seed production, these lipids accumulate in the plant tissues - leading to higher resin production in glandular trichomes. The same increase in lipids responsible for the significant increase in resin production also plays a major role in the physical properties of bud, most notably how it burns. This is because lipids, unlike many of the other hydrocarbons found in plant tissue, do not oxidize and form H2O and CO2 through normal combustion reactions. Lipids instead undergo a process called Pyrolysis, a chemically complex and inefficient process that releases many byproducts.

Most commercially available 'Flushing Agents' contain what are known as Chelating agents, molecules that bind to metal ions to form a stable, water-soluble complex. The use of chelating agents in agriculture outside of "flushing" purposes is well known, intended to increase the efficacy of micronutrient applications on cash-crops (the use of micronutrient chelates is limited to cash crops due to their high cost of application). Unbound chelating agents such as free-form EDTA (the primary active ingredient in most flushing solutions) are effective at increasing the solubility and mobility of metal ions in soil and other growing mediums. Combining this increase in solubility and mobility with an increase in watering frequency undoubtedly decreases the concentration of available nutrients in the growing medium, which in turn lowers raises the osmotic pressure of the soil. Plants absorb nutrients because sugar, the primary molecule present in a plants sap, raises the osmotic pressure of the roots above that of the soil resulting in the transport of dissolved nutrient ions. Without this osmotic pressure gradient, the transport of nutrients across the plants' cell membrane and assimilation of nutrients into the plants' tissue cannot occur.

http://www.els.net/WileyCDA/ElsArticle/refId-a0001918.html Plant Storage Lipids
http://www.sciencedirect.com/science/article/pii/S0163782712000410 Phosphate Starvation & Membrane Lipid Remodeling in Seed Plants
https://www.coresta.org/abstracts/effect-air-curing-chemical-composition-tobacco-8647.html Effect of air-curing on the chemical composition of tobacco
http://pubs.acs.org/doi/abs/10.1021/jf60161a012 Thermal Degradation of Lipids
http://onlinelibrary.wiley.com/doi/10.1046/j.1365-3040.2000.00595.x/pdf Nitrate uptake and reduction in higher and lower plants
http://pubs.rsc.org/-/content/articlelanding/1937/tf/tf9373301006 Salt Accumulation By Plants
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5147430/ Synthetic Chelating Agents and the EDTA Shuttle-Effect
http://scholar.lib.vt.edu/ejournals/JARS/v55n3/v55n3-hammer.htm Osmosis & Plant Nutrition

 

stnr420

Well-Known Member
"Flushing", although a common practice amongst Cannabis growers, is one with a limited amount of information. Although most growers cannot explain the science behind the flushing process, many swear by it from experience, claiming it leads to buds that burn "cleaner" and with better flavor.

Studies show that when excess nitrates are present in the soil, higher plants (including herbaceous plants such as Cannabis) accumulate nitrate, storing it in organelles called vacuoles where it may exist in concentrations as high as 100 mM. In order for plants to mobilize this stored Nitrate, Nitrate supply must drop below nitrate demand. Phosphorus is mainly used by plants for the synthesis of lipids, and it is in these lipids where the plant stores the majority of its phosphorus content. Unlike Nitrogen/Nitrate, Potassium deficiency results in the degradation of lipids and the mobilization of phosphorous through the break-down of phospholipids. These lipids are primarily found in chloroplast membranes and consist of glycerol to which is attached one or two sugar molecules and two fatty acids. The process of breaking down phospholipids to mobilize phosphorus during phosphate starvation is referred to as Membrane Lipid Remodeling. One effect of Membrane Lipid Remodeling is that it causes the cells to disintegrate, causing the content of the cells (including nitrate) to be made accessible for further mobilization. One made available, Nitrates can undergo nitrosation reactions with Alkaloids present in the Cannabis plant (Similar reactions occur in Tobacco primarily during the air-curing process). Due to the fact that unpollinated Cannabis is much higher in lipid-containing oils that would normally be used for seed production, these lipids accumulate in the plant tissues - leading to higher resin production in glandular trichomes. The same increase in lipids responsible for the significant increase in resin production also plays a major role in the physical properties of bud, most notably how it burns. This is because lipids, unlike many of the other hydrocarbons found in plant tissue, do not oxidize and form H2O and CO2 through normal combustion reactions. Lipids instead undergo a process called Pyrolysis, a chemically complex and inefficient process that releases many byproducts.

Most commercially available 'Flushing Agents' contain what are known as Chelating agents, molecules that bind to metal ions to form a stable, water-soluble complex. The use of chelating agents in agriculture outside of "flushing" purposes is well known, intended to increase the efficacy of micronutrient applications on cash-crops (the use of micronutrient chelates is limited to cash crops due to their high cost of application). Unbound chelating agents such as free-form EDTA (the primary active ingredient in most flushing solutions) are effective at increasing the solubility and mobility of metal ions in soil and other growing mediums. Combining this increase in solubility and mobility with an increase in watering frequency undoubtedly decreases the concentration of available nutrients in the growing medium, which in turn lowers raises the osmotic pressure of the soil. Plants absorb nutrients because sugar, the primary molecule present in a plants sap, raises the osmotic pressure of the roots above that of the soil resulting in the transport of dissolved nutrient ions. Without this osmotic pressure gradient, the transport of nutrients across the plants' cell membrane and assimilation of nutrients into the plants' tissue cannot occur.

http://www.els.net/WileyCDA/ElsArticle/refId-a0001918.html Plant Storage Lipids
http://www.sciencedirect.com/science/article/pii/S0163782712000410 Phosphate Starvation & Membrane Lipid Remodeling in Seed Plants
https://www.coresta.org/abstracts/effect-air-curing-chemical-composition-tobacco-8647.html Effect of air-curing on the chemical composition of tobacco
http://pubs.acs.org/doi/abs/10.1021/jf60161a012 Thermal Degradation of Lipids
http://onlinelibrary.wiley.com/doi/10.1046/j.1365-3040.2000.00595.x/pdf Nitrate uptake and reduction in higher and lower plants
http://pubs.rsc.org/-/content/articlelanding/1937/tf/tf9373301006 Salt Accumulation By Plants
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5147430/ Synthetic Chelating Agents and the EDTA Shuttle-Effect
http://scholar.lib.vt.edu/ejournals/JARS/v55n3/v55n3-hammer.htm Osmosis & Plant Nutrition
For years ive said i flush....as it turns out...i dont....well according to riu standards...do i dump 3x the volume of water? Fuck no... That would drown my plants....i just use plain ph water the last 2 weeks...and this round....imma do a week enzymes..sugars...compost tea.....then a week just plain water...
 

SonsOfAvery

Well-Known Member
The argument is already going on here...still, for some reason.
http://rollitup.org/t/flushing.950432/page-7#post-13820859

I think the main problem people are having is with the terminology.
Flushing water at 3x the volume of the pot is essentially pointless...I less you've fucked up and need to totally reset the grow medium.
There are argument's to be had for flushing in the sense of using a water only or weaker solutions towards the end of flowering.

But personally, no flush for me, just a correct feeding schedule from start to finish. And "flushing" won't be needed.
 

chemphlegm

Well-Known Member
Studies show that when excess nitrates are present in the soil, higher plants (including herbaceous plants such as Cannabis) accumulate nitrate, storing it in organelles called vacuoles where it may exist in concentrations as high as 100 mM. In order for plants to mobilize this stored Nitrate, Nitrate supply must drop below nitrate demand.
awesome, I must be providing the soil with the perfect amount of nitrates, instead of excess amounts.
I flush with water for around 9 days, right after I add a cup of dry organic composted chicken shit, every 9 days. I add
one gallon of water to the promix only when the bucket is dry to the bottom, right before the plant wilts. A small amount of run off sometimes results.
Only a pure water flush for the next 9 or so days. I harvest right before the last (non) addition of fertilizers, at the end of that flush period.
 

cannetix Inc

Well-Known Member
By Flush do you mean leach the medium of salts or do you mean water the plant?

I grow in soil and I water the pots. Am I flushing not watering?


These stoner terms do my head in sometimes...

The primary difference between watering and flushing would be volume. For watering, under ideal circumstances, you want to saturate soil while allowing for minimal amounts of run-off. This is why the use of drip irrigation systems is so common in agriculture. Run-off water contaminated with dissolved Nitrates and Phosphates is one of the primary environmental concerns associated with agriculture.

https://www.ncbi.nlm.nih.gov/pubmed/11837440 Nutrient concentration in agricultural runoff and resulting effect on plant growth
https://www.epa.gov/nutrient-policy-data/estimated-animal-agriculture-nitrogen-and-phosphorus-manure

One of the key methods aimed at preventing such pollution is the control of run-off through efficient irrigation techniques. Logically, if run-off does not occur, Nitrates and Phosphates will not be leached from the soil. Most of a plants feeder roots exist in the top 12" of soil so nutrients that leach below this depth will have difficulty being absorbed by the plant.
 

Lucky Luke

Well-Known Member
The primary difference between watering and flushing would be volume. For watering, under ideal circumstances, you want to saturate soil while allowing for minimal amounts of run-off. This is why the use of drip irrigation systems is so common in agriculture. Run-off water contaminated with dissolved Nitrates and Phosphates is one of the primary environmental concerns associated with agriculture.

https://www.ncbi.nlm.nih.gov/pubmed/11837440 Nutrient concentration in agricultural runoff and resulting effect on plant growth
https://www.epa.gov/nutrient-policy-data/estimated-animal-agriculture-nitrogen-and-phosphorus-manure

One of the key methods aimed at preventing such pollution is the control of run-off through efficient irrigation techniques. Logically, if run-off does not occur, Nitrates and Phosphates will not be leached from the soil. Most of a plants feeder roots exist in the top 12" of soil so nutrients that leach below this depth will have difficulty being absorbed by the plant.
So you mean leaching. Why not use the correct horticultural term.

Of cause leaching has its place if you over feed. Don't over feed and there is no need to leach. This doesn't really require yet another thread on the topic. One seems to pop up every week.

http://rollitup.org/t/flushing.950432/
 
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cannetix Inc

Well-Known Member
So you mean leaching. Why not use the correct horticultural term.

Of cause leaching has its place if you over feed. Don't over feed and there is no need to leach. This doesn't really require yet another thread on the topic. One seems to pop up every week.

http://rollitup.org/t/flushing.950432/
Leaching is the process occurring in the soil. I don't use this term because it isn't exactly correct to say. Flushing is an action, leaching is a process. Flushing is done intentionally to leach nutrients from the soil, but leaching may also occur as the result of natural run-off. Assimilation is the chemical process responsible for nutrient uptake/absorption, but you don't say you are "assimilating plants", you say fertilizing. Then again, the terminology really isn't worth debating over at all, and at the end of the day, you are right about it.

Maybe it would help if I clarified some terminology.

Yes, by flushing I do mean the process of leaching nutrients

The term "Salts" in this case is being used interchangeably, referring to both common fertilizer salts (Nitrates & Phosphates) as well as salts such as Sodium Chloride (Which accumulates in plants and is toxic to them even at low concentrations). "Salt" is a broad term that refers to an ionic compound that can be formed by the neutralization reaction of an acid and a base


http://www.faculty.ucr.edu/~jkzhu/articles/2007/ELS Zhu.pdf Salt Toxicity In Plants

Leaching certainly does have its place if you over-feed, but it isn't just about over-feeding as the studies I linked quite clearly indicate. Excess Nitrates, as well as Sodium Chloride, will not accumulate if there is no excess present, but these are just two pieces of a very complex puzzle.

Please refer back to the link provided pertaining to the degradation of lipids under potassium deficient conditions.

http://www.els.net/WileyCDA/ElsArticle/refId-a0001918.htmlPlant Storage Lipids
http://www.sciencedirect.com/science/article/pii/S0163782712000410Phosphate Starvation & Membrane Lipid Remodeling in Seed Plants

It's also worth referring back to the information provided on osmotic pressure & sugars in the plants' sap. Dried cannabis, like any other part of any other plant, still contains the dehydrated remains of its sap, which consists predominantly of sugar - and thus any nutrients chelated by said sugar. Sugars, including Glucose, Fructose, and Sucrose are all form colorless solutions in their pure form. Saps and sap products such as Maple Syrup and Molasses exhibit a dark color due to the presence of impurities, which includes dissolved mineral salts and metal chelates.

http://scholar.lib.vt.edu/ejournals/JARS/v55n3/v55n3-hammer.htm Osmosis & Plant Nutrition
http://nutritiondata.self.com/facts/sweets/5573/2 An example of the presence of nutrients & trace elements plant sap and sap based products

Another aspect of flushing/leaching worth investigating, although I'm unsure if it already been addressed in other threads, is the fact that plants don't just have a demand for nutrient uptake, but also produce waste products (although such waste products may not be directly produced by the plants themselves). One such example of a waste product that will be present in soil regardless of feeding habits is Ammonia. Ammonia is produced by bacteria in water and soil as an end product of plant and animal waste decomposition. Under normal growing conditions, Ammonia will be converted to Nitrite, and then to Nitrate, the form of Nitrogen plants require. When there is still a high demand for nitrogen this isn't a problem, however, That being said, this process is not instant, and Ammonia present in the soil can be and is absorbed by the plant.

https://link.springer.com/article/10.1007/BF00547988 Ammonia Uptake By Plants

Personally, I've had good experiences with flushing, even with my minimal fertilizer application, and even outside of the Cannabis culture. In my experience, even food crops harvested without a "flush", especially if quick-release salt based fertilizers have been used have a strong, sometimes metallic taste. From the countless studies I've read on the matter, the science seems to support it - so with that, I'm just curious if you have any real data that contradicts these findings, or are you simply speaking from experience?
 
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