[micronutrients] Is non-water-soluble iron simply 'slow-release', or is it wasted?

[SU2]

In an effort to combat chlorosis in some bougies (commonly caused in bougies by iron and/or magnesium deficiencies), I got a pretty 'balanced' minerals formula (no NPK) to use as I knew that iron&magnesium compete for uptake (so if I tried dosing just one, and it was the wrong one, I could've just exacerbated the problem)

Anyways I've been wondering about something on the label that just didn't sit right with me, the product lists pretty hefty magnesium (4%) and iron (7.5%) contents but, upon further inspection, only tiny amounts (.19% and .25%, respectively) of those totals are 'water soluble' - does that mean that the remainder of the mineral (which is the overwhelming majority in this case) is merely slow-release, or does that mean it's unused by the plant? Here's the label:


Am also a bit confused by why there's so much sulfur in it, can't say I've heard of supplementing sulphur yet it's one of the highest concentrates in this product!

(interesting side-note re 'water-soluble' is that, if you put some a tsp of these granules in a cup of water, within a day - probably less I just didn't try to get more precise - they've broken-down to what looks like a solution with a little bit of a suspension in it - I imagine the 'suspension' part is the non-water-soluble stuff?)

 

[GrimLore]

The label indicates it is a slow release near the bottom so I could only guess what your seeing mixed with water breaks down more over time.

I find it odd they list a percentage of Sulfur but do not list it as an ingredient. I find watering in a solution of Sulfur to be of benefit but it should be also listed as an ingredient

I also don't understand why Calcium Sulfate is listed. I could be wrong on this but I don't see adding a desiccant to be of any value.

Interested to see what @0soyoung thinks about it for certain

Grimmy

 

[0soyoung]

This is Paul's {from Austrailia) bailiwick.

However, I think the primary purpose of these 'greeners' is to acidify the soil as this is the main thing that prevents the uptake of iron that is the usual cause of chlorosis. The sulfur content is almost solely to acidify the soil, making a weak sulfur acid. with water in the soil. The iron content is to 'to be sure' that there really is enough iron in the soil.

I still find it fascinating that Mg is the focal element in the chlorophyll molecule. Iron, on the other hand, is a thylakoid membrane element that is key to photosynthesis, but not part of chlorophyll, per se (IIRC). Yet a shortage of iron affects chlorosis; rarely Mg. Many growers of roses, maples, and hinoki cypress swear by liberally sprinkling Epsom salts (magnesium sulfate) about the roots of their plants to keep their foliage dark green. It is hard for me to tell what effect it has, but maybe the leaves indeed are a darker green than they would have been.

 

[GrimLore]

The sulfur content is almost solely to acidify the soil, making a weak sulfur acid. with water in the soil.

That part I fully understand, I just don't see it listed as an ingredient on the package

I also don't understand why Calcium Sulfate is listed. I could be wrong on this but I don't see adding a desiccant to be of any value. Thoughts?

Grimmy

 

[0soyoung]

I also don't understand why Calcium Sulfate is listed. I could be wrong on this but I don't see adding a desiccant to be of any value.

That is gypsum and it is used to 'open up' clay soils relieving problems with hardpan (or moss overtaking a lawn). Ironically, this problem with 'tight clay' often arises because of excessive magnesium (built up levels from chem fert over a long term of several years). The advantage of gypsum over horticultural calcium is that it doesn't change the soil pH. Horticultural calcium is used for similar reasons, but makes soil less acidic.

This stuff doesn't look to be useful in a bonsai context, IMHO. A pinch of Ironite (greener not their fertilizer) has worked for me as a chlorosis remedy (for my bonsai and also my landscape plants). Alternatively one can buy straight iron sulfate. It can also be applied as a foliar spray for quick response (but the substrate will still need to be treated).

Florida generally has infamously hard water, so I think the OP either needs to change the pH of the water applied or use a soil acidifier fairly frequently. A fertilizer made for azaleas/rhododendrons or Miracid might be enough.

 

[GrimLore]

Florida generally has infamously hard water, so I think the OP either needs to change the pH of the water applied or use a soil acidifier fairly frequently. A fertilizer made for azaleas/rhododendrons or Miracid might be enough.

Thank you for the clarification on the Calcium Sulfate.

I have been simply watering in Sulfur as an acidifier with good results. I buy the Sulfur powder 99.9 percent powder for roses and mix 2 tablespoons to 1 gallon of water. The Azaleas and such do good with a bi weekly application. I also use the same solution on all of my fruit trees 3 times a year and it breaks the cedar rust cycle nicely.

Grimmy

 

[SU2]

I find it odd they list a percentage of Sulfur but do not list it as an ingredient. I find watering in a solution of Sulfur to be of benefit but it should be also listed as an ingredient

Is it a good % of sulfur? Honestly I was unaware sulfur was a plant nutrient, I would've guessed it to be a bad thing... But if it's needed, glad it's in there! Just wondering if it's a 'good' dose or not

 

[SU2]

Florida generally has infamously hard water, so I think the OP either needs to change the pH of the water applied or use a soil acidifier fairly frequently. A fertilizer made for azaleas/rhododendrons or Miracid might be enough.

I thought that using miracle gro was sufficient, I know my main specie (bougainvillea) prefers acidic soil so would hate to know I was running more alkaline than norm!!

 

[SU2]

Thank you for the clarification on the Calcium Sulfate.

I have been simply watering in Sulfur as an acidifier with good results. I buy the Sulfur powder 99.9 percent powder for roses and mix 2 tablespoons to 1 gallon of water. The Azaleas and such do good with a bi weekly application. I also use the same solution on all of my fruit trees 3 times a year and it breaks the cedar rust cycle nicely.

Grimmy

Very interesting! I'd been using miracle gro and thought that synthetic fert inherently made my soil more acidic (and that that'd be sufficient), my main plants are acid-loving types so am going to have to get my FL water tested to know pH, good to know my minerals formula offers some help but may need to get pure sulfur for long-term use like you mention if it turns out my water is more on the alkaline side!