thetr33man
Well-Known Member
Great splanation of cal/mg/p issues. Ive been struggling a lot with some non weed plants indoor under LED and this might help me straighten things out...Look closely at the plant at the top left: that is the start of a calcium-magnesium deficiency. As calcium also affects uptake of phosphorous, you will see signs of P deficiency as well.
So how to tell if it's a Ca-Mg deficiency and not P toxicity (that locks out Ca-Mg and shows similar symptoms)? In this case, the affected plant is the biggest, healthiest, fastest-growing plant - it makes sense it is suffering a deficiency, as it has the highest nutrient demands.
Secondly, P toxicity usually first shows up as burning around the leaf margins, whereas Ca/P deficiency shows up as random "rust spots".
Mg deficiency - before it gets to the interveinal chlorosis stage (yellowing between the leaf veins) - can be seen with slight curling of the leaf margins.
Finally, I had run out of de-chlorinated water, so decided to use RO water. The deficiency showed up straight away, as the natural Ca and Mg in the tap water was missing in the RO water.
I dechlorinate my water to propagate beneficial microbes in my coco at the root zone from the organic-based nutrients.
One issue with coco is that it is susceptible to Ca-Mg deficiencies. The fibres - which usually contain naturally high levels of Na-Cl (sea salt) - will ion exchange, bonding the Ca-Mg and releasing the Na-Cl. Coco naturally bonds with free metal ions, so will lock up Ca-Mg.
Mg is instrumental in photosynthesis, whilst Ca is very important to the onset of flowering, aiding flower development.
I see a lot of Ca-Mg deficiencies on these boards that are not deficiencies at all!
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I dosed this plant pretty good with epsom salt and it took off but has kind of stalled out again now...