Osmocote and pH

[Jester]

Hi there crazy kids!!

I've seen it mentioned a few times that prolonged use of Dynamic Lifter can cause the soil to go alkaline. Can the opposite apply for Osmocote?. I have a coffee tree and have been using Osmocote consistently for about 4 years on it. I measured the pH and it was very acid at 4.8. If it's not the Osmocote I'm not sure what else it could be. I'm wondering whether it's the breakdown of certain salts in Osmocote that might be causing this. Can anyone help? Actually, now that I think about it, the tree in question is about 5 years old and only 2 inches high and displays all the signs of an iron deficiency.(Yes I know I can add iron chelate to the soil but that's not the mission here) The other tree, which I bought on the same day was allowed to grow normally and is now about 1 metre high and is completely healthy. I'm just wondering if keeping the tree so small can have a reverse effect on the soil somehow. From everything I have studied so far in horticulture you would'nt think so but there is something big missing here. I wish to understand from a chemical / mineral perspective how this situation has come about. Joel where are you???? A lack of Potassium inhibiting uptake of Iron??

edit: I have another theory, tomorrow morning I am going to take the tree out of the pot and see if there is anything suspicious in there.

John

[Jamie]

Gday John!

i dont think keeping the tree small would be inhibiting or changing the soil in anyway. especially if your other one is booming. what i have learnt about ferts is that to much of one nutrient whether it be macro or micro can inbalance others. im not sure exactly which is does what i would have to go through my studies but for an example high amounts of nitrogen can cause other micro nutrients an inefficient ability for the tree to take up or basically deplete it. now i cant remember where in my studies i learnt that it can happen but i will see if i can remember it and get back to you

J

[Jester]

Hey Jamie and hey all. Well I can now say at the very least I found the problem causing the small leaves and pale colour. .....Root Rot!! The roots were so limp and lifeless, I could tear them apart with very little effort and as you can see in one of the photos, the outer wall of the root is easily separated from the main portion inside. I am still not entirely sure why the pH had dropped down so much by my initial suspicion is too much Osmocote for such a small pot of soil for far too long. I am still open to other theories.

John

[63pmp]

Hi Jester,

Here is a breakdown of what osmocote total all purpose has in it, I got this of the Scotts osmocote website in the USA. I think what we have here in australia is the same, just re-badged.


Osmocote Total All Purpose

Active ingredients Concentration as %

Ammonium nitrate 20-35%
Mon-ammonium phosphate <5%
Urea 10-15%
Magnesium sulphate <1%
Magnesium oxide <1%
Potassium nitrate 20-35%
Boric acid <1%
Iron sulphate <1%
Copper, iron, manganese
and zinc EDTA <1%
Sodium molybdate <1%
Non-ionic surfactants 2-5%
Alkyd resin coating -

(sorry for the formatting, its hard to do tables on this site)

As you can see its mostly nitrogen, some pottasium, and a little bit of phosphate. Nitrates raise soil pH, Urea and ammonium lower it. Its hard to say just by looking at it, but it would probably err on the acid side of things to prevent the ammonium and urea turning into ammonia, which is toxic to plants. It depends on what leaches out first. Urea is highly soluble so it might dump first and lower the pH. Anyway you look at it, the product is not well balanced, as there is practically no magnesium and has no calcium, its also expensive for what you get, as most of these ingredients are like a dollar a kilo at a farmers supplier.

Water logging, or poor draining soil will cause an increase in acidity, ie lowering of pH.

Paul

[Jester]

Hey Paul thankyou VERY much for that fantastic and informative reply. I have just come home from a long day and by brain is the consistency of cut paste. I will have to get a cup of coffee in the morning and have another read to digest it all.


Thanks again mate

John