What's wrong? (6 weeks flowering)

[dre86]

A bit late, but better late than never..I was wondering what wrong.

My plants ' leaves turn yellow in middle flowering (5-6 weeks out of 8-9). Have I underfert them? I give them organic bloom fert 1.5-13-14 once a week. It starts from the tips and works it way up to the middle of the leaf until turns brown and dies. Also the stem of the leaf turns purple. What's wrong?

Here's a pic:

MasterKush

Super Thai x Skunk

 

[sproutco]

Are they growing in just hydroton or is there soil in there too? Is there magnesium in your ferts?

 

[borat]

i think they all looks just fine..

my leaves also begin to yellow around week 6 with or whitout fertz..

 

[stretchpuppy]

I think your photo belongs in the Photos section and not the Infirmary. Looks great dre. A little more N at the onset, in organic form, may help... but mine always tend to go yellow late in flower too, esp. 6 weeks +.

Less is more as far as I'm concerned, and I'd rather have slight yellow than burnt tips.

Sorry I can't be more specific... that's what sproutco is here for though!

 

[dre86]

Are they growing in just hydroton or is there soil in there too? Is there magnesium in your ferts?

They are in organic soil with some hydroton pebbles mixed in, and a little on top but that doesn't do much

There are no epsom salts / magnesium etc in the soil nope so the yellowing would be caused by a lack of magnesium??

My bloom fertilizer is Ata Organics :

Bloom-C is a liquid yield-increasing organic fertilizer made primarily from algae and seaweed extracts. It contains a rich mixture of amino acids, trace elements, vitamins, enzymes and natural plant hormones. Add from bloom forming. Do not use in combination with lime!

So it is completely normal, or not? They are at 7 weeks today and more and more leaves turn yellow, then brown and shrivel

edit: these are the big fan leaves, not the leaves on the buds. The yellowing starts from the tip and works its way up till the middle. The whole leaf is yellow then and shrivels up and dies. I think this negatively affects my yield?

 

[badboyg]

I see no photos // BUT sounds like the normal drop off as they finish,, me I never get that far,, the bugs kill most mine before they fall naturaly.. WAAA,,,

 

[sproutco]

Potassium, calcium, and magnesium all compete against each other. This is called cation antagonism or cation competion (cation=positively charged).

When you apply alot of potassium, you should ensure that calcium and magnesium levels are good otherwise a deficiency will occur. Since you have not potted in quite a while, any dolomite lime in the soil is probably running down...less cal mag around. High potassium will cause a magnesium deficiency first and then calcium second. You want a ratio of 4:2:1 potassium to calcium to magnesium in your ferts/soil.

When plants begin flowering this stressful. These plants have a high mag requirement. Magnesium deficiency will really come out when there is stress.

If there is no calcium and magnesium in your ferts, you should add these every third fert or so to keep up levels when dolomite is in the soil and every fert if no dolomite lime in the soil or supplies run low. This keeps a balance between the 3 elements when potassium is all your really applying. 1/4 teaspoon (1.25ml) both epsom salts and powdered gypsum per gallon (3.8L) of water along with your regular ferts.

Since it looks like you have a bad case of magnesium deficiency starting, drench the soil with 2 teaspoons (10ml) epsom salts per gallon (3.8L) of water as a one time cure rate. Magnesium def. is hard to cure once started but this may help.

In the future, you may want to add 1 teaspoon (5ml) epsom salts per gallon of water and drench once at the beginning of flowering especially if you intend on applying large doses of potassium. Maybe this early high rate application will ward off a later deficiency.





In both soil and soilless mixes, adjust your ph to about 6 after mixing the fert water. This will ensure no ph surprises.

 

[420KushMaster]

dude they look normal

 

[dre86]

ok thx, it's normal then.

 

[peafunk]

that kooks like great lookin plant

 

[sproutco]

ok thx, it's normal then.

No its not normal. Your plant is having to feed off its shade leaves in order to flower.

 

[guineapig]

oh jeez.....sproutco don't tell him its not normal, you will worry him!!!

The fan leaves droop a bit and start to drain of their dark green colour as the Nitrogen
is a mobile element which the plant can use when it needs it....the yellowing is completely normal, except that ideally you would want to see this happen at the last 2 weeks of flowering instead of the 2 middle weeks.....

Your particular variety of plant probably uses a bit more nitrogen than other varieties of Cannabis.....no big deal at all....

My theory is that the plant senses it is dying and just does this instinctively....the drooping leaves allows more light to shine on the buds and the fan leaves drain their nutrients so that the buds can use them......

I would just continue as normal, just keep on doing what you are doing and don't change anything....

-gp

 

[inflorescence]

Potassium, calcium, and magnesium all compete against each other. This is called cation antagonism or cation competion (cation=positively charged).

Sproutco, can you explain this concept please. I understand CEC but what I don't understand from what your saying is why one cation will inhibit another cation from uptake. Can't plants uptake more than one cation at a time? So, for example, if there are equal number of cations in the rhizosphere what would cause the ca++ cation to inhibit the uptake of the K+ cation or vice versa? Jorge Cervantes says MJ will uptake Na+ before any other nute but this would seem to be a concept of cation preferentialism rather than antagonism so apparantly there are two different cation forces at work here?
Is there such thing as anion antagonism? Also, why is one cation absorbed more than another similar cation at the same pH? It would seem like all cations would be absorbed equally at a certain pH and the same for anions.
Also, I assume "lockout" is a different concept in that in the case of lockout I assume one ion like ca++ binds with another like P (precipitates into an insoluable form, calcium phosphate) and this is what causes the lockout as opposed to mere antagonism? I know pH can "lockout" the absorbtion of an ion but again, why do anions and cations absorb at different pH's?

 

[guineapig]

Cation Exchange

The inorganic nutrients taken in through the roots of plants are present in the soil solution as ions. Most metals form positively charged ions, that is, cations, such as Ca++, K+, and Na+. Clay particles provide a reservoir of such cations for the plant- at various points on the crystalline lattice of the clay there is an excess of negative charge, where cations can be bound and thus held against the leaching action of percolating soil water.
The cations bound in this way to the clay particles can be replaced by other cations (in a process called CATION EXCHANGE) and then released into the soil solution, where they become available for plant growth. This is one reason why clay particles are an essential component of productive soils.
The principal negatively charged ions, or anions, found in soil are NO3-, SO4--, HCO3- and OH-. Anions are leached out of the soil more rapidly than cations because anions do not attach to clay particles. An exception is phosphate, which is retained against leaching because it forms insoluble precipitates. Phosphate is specifically adsorbed by, or held on the surface of, compounds containing iron, aluminum, and calcium.
The acidity or alkalinity of soil is related to the availability of inorganic nutrients for plant growth. Soils vary widely in pH, and many plants have a narrow range of tolerance on this scale. In alkaline soils, some cations are precipitated, and such elements as iron, manganese, copper, and zinc may thereby become un-available to plants. Mycorrhizae (see Chapter 12) are especially important to the absorption and transfer of phosphorous in most plants, but these structures have also been implicated in the increased absorption of manganese, copper, and zinc by plants.

(Biology of Plants, 5th edition, reprinted without permission.....)

Sproutco- what is your source on this cation competition idea?

Infloresence- are you trying to better understand the concept of "nutrient lockout," such as when the pH shifts into the alkaline region and thus prohibits the absorption of certain nutrient ions? Or are you talking about the deficiencies that occur when a huge quantity of one nutrient is dumped in the soil, thus locking out other ions? From all i have read, i think the term "nutrient lockout" applies to both situations and is just a general term used to explain why plants do not absorb certain nutrients even though an excess of certain nutrients are physically present in the soil......

I do not wish to confuse so feel free to pm me if i have confused you....

guineapigs among us

 

[inflorescence]

No confusion here guineapig.

Or are you talking about the deficiencies that occur when a huge quantity of one nutrient is dumped in the soil, thus locking out other ions?

High potassium will cause a magnesium deficiency first and then calcium second. You want a ratio of 4:2:1 potassium to calcium to magnesium in your ferts/soil.

I'm just trying to figure out, why one cation (K+) needs to be present in a larger ratio than another cation (ca+).

I can't make the connection how this "competition" between these could be caused by pH.

 

[sproutco]

I'm just trying to figure out, why one cation (K+) needs to be present in a larger ratio than another cation (ca+).

The absorbtion of cations is thus more or less a non specific process, depending mainly on the concentration of the cation species in the nutrient medium and in some cases also on the specific permeability of membranes to particular cation species (facillitated diffusion). For this reason non specific competition between the cation species for the negative charges of the cell may occur. Increasing the supply of one cation species in the nutrient medium can thus depress the levels of other cation species in the plant. The cell produces anionic equivalents which attract and retain cations non specifically. This attraction can be likened to a race for uptake between the individual cation species. The cation taken up fastest will neutralize the anion equivilents first and thus reduce the electostatic attraction for the other cation species. The uptake rate depends on the concentration of the individual cation species in the nutrient solution. Potassium which is taken up by the cell rapidly competes strongly in cation uptake. In the absence of k in the nutrient solution the uptake of other cation species is thus much enhanced because competition for uptake is less severe.