This is the most confusing thread to me , sorry I just don't want to mix my own nute mix ....
please recommend some products and discuss there use with different water types (RO /Tap) and perhaps some
discussion on concentration used in different stages of plant growth ....
I have read most of the links that have been posted , but could you simplify ....
I have collected some posts from Al B. and Heath Robinson and would like your comments....
Thanks U B I've been trying to locate a source for Dyna-Grow F Pro but after FatMans posts I'm confused ...
Here are the posts, thanks in advance O. F. D.
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Posted by Heath Robinson....
https://www.rollitup.org/hydroponics-aeroponics/149998-heaths-flooded-tube-vertical-54.html#post3053154
I will go into detail about nutrient concentrations because it seems to be an area which a lot of growers don't fully understand.
I have seen quite a lot of bad advice from experienced growers who advise to "increase the nutrient concentrations until you see tip burn and then back off slightly" I will try explain why this is bad advice.
Nutrient salts can cause harm to plants if they are in high enough concentration in water or soil. This effect is mainly indirect by pulling moisture out of roots and reducing the uptake of water and nutrients to affected plants. This is the cause of tip and edge burn of leaves, if the nutrient concentration was maintained, slow growth, nutrient deficiencies, wilting and eventual death of the plant would occur if the problem is not corrected.
This is the reason why, Water movement in plants is a factor of osmotic pressure and capillary action. Osmotic pressure is defined as water flowing through a permeable membrane in the direction of higher salt concentrations. Water will continue to flow in the direction of the highest salt concentration until the salts have been diluted to the point that the concentrations on both sides of the membrane are equal.
A good example of this is pouring salt on a slug or snail, the salt concentration outside the slug is highest, which causes the water from inside the slug's body to cross the skin membrane. The slug becomes dehydrated and dies.
For osmosis to occur, water must move from a more dilute (the nutrient solution) to a more concentrated compartment (the plant). If you were to water your plant with sea water the plant would wither and die as the salt water now extracts water from the plant instead of replenishing it. So basically high levels of salinity will lead to high concentrations of salt in the plant tissues which will severely damage metabolic processes.
here is a grow chart which will help explain why there is no advantage to feeding your plants high nutrient concentrations.
notice on the chart that there is a deficient zone where the plant is not meeting its needs and growth is poor. A low zone where the plant is growing but lacks all the necessary nutrients to sustain good growth and yield.
Now the important part, you will notice if you look at the sufficient and high zones that there is no advantage to feeding your plants at higher concentrations than is needed. Notice also that growth and yield suffers sharply once the plant is over fertilised. If you feed your plant until it is toxic and showing signs of tip burn and you back off slightly you are still in the excess zone and your yields will suffer to some degree.
I have found that the sufficient zone for marijuana is in the range from an Ec of 1.0 to 1.6 I personally run in at an EC of approx 1.2 and never exceed 1.4
I hope that helps explain why I do what I do.
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Al B. Fuct says
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https://www.rollitup.org/hydroponics-aeroponics/198817-nutrient-question.html)
I use Canna 2-part nutrients. My standard mix is 375ml "part A" and 375ml "part B" in a 100L reservoir. Should yield a tank at 1300-1500ppm depending upon residual mineral salt content of the make-up water.
Fertiliser composition is represented by a three figure expression like 10-10-10, 5-10-5, etc. The figures represent the ratios of the principal elemental nutrients N (nitrogen), P (phosphorus) & K (potassium) to one another.
Cannabis prefers a high ratio of N to P & K for vegging, i.e. 20-10-10, 10-5-5, etc. In both examples, N exists in twice the amount compared to P & K. 20-10-10 would have twice as much N, P & K as 10-5-5.
For flowering, cannabis needs a high P nutrient such as 10-20-10, 5-10-5, etc. Note that the figure for P is greater than those for N & K.
Avoid extremely high P nutes like 10-50-10 (African violet food). There's too much P for the N & K and this has been known to cause what looks like an N deficiency in cannabis. You can use P based 'bloom boosters' (such as Canna PK-13-14) in late flower (week 6 of flowering, use for 1 week only), but stick with a more moderate P ratio for weeks 1-5 and 7-8. You may want to stop using nutes altogether in flowering weeks 7-8. The plants will store right on 2 weeks worth of nutes anyway.
I'm not sure of any established optimal NPK for flowering, but I do know that 10-50-10 African violet food has given many ppl grief. I'd stick to a 1:2:1 ratio, i.e. 5-10-5, 10-20-10 or thereabouts for flowering. Some ppl use P & K based 'bloom boosters' (such as Canna PK-13-14 and imitators) for 1 wk only in week 6 of flowering, which in addition to usual flowering nutes, can yield a very high P number. You can P burn badly with P boosters, so start with 1/4 the mfr recommended dosing and use it for only 1 week in wk 6.
I've recently rebuilt my op with 125L tanks for each of my 820mm square flood trays, each which hold 23 plants. It previously had 100L tanks. These days, with the bigger tanks, ppm stays constant all the way to the minimum water level, which is whatever it takes to fill the flood tray to the overflow and still keep the pump submerged.
With the smaller tanks, as water level dropped, the ppm would rise slightly each day. I mix for 1400ppm; by day 4-5, the tanks would bump up as high as ~1500-1600ppm with about 70% of tank volume remaining. Adding water of course dropped the ppm back to 1400. However, filling the tank to the top would yield often as low as 900ppm, the difference between 1400 and 900 being what the plants had eaten. In this case, the plants were using a certain percentage of the water faster than the percentage of the nutes. I stop adding water when the meter says ~1100ppm.
The larger tanks stay right on 1400 as water level drops. The volume of water is apparently better matched to the nutrient consumption rate. If I refill with water, the ppm will drop, by a somewhat lesser amount than with the smaller tanks.
I'm happier with the consistent 1400 and am learning to live with looking at a half-empty tank- if there's enough to keep the pump submerged on flood, all is well. I'm resisting the urge to top tanks for the entire 2 weeks if possible. If air temps are warm, evaporation increases, forcing me to add some water, but I don't totally refill the tanks.
