Boron & Calcium for mature/in-ground mango tree. How much and when??

[JakeFruit]

Like many of you, I watched the Gary ZIll video on E-4 Sugarloaf recently posted on here. I came away with a few nuggets of wisdom, but also the question of how much Boron & Calcium I should be using and when. My smaller mangos all get fertilizer with micros, so pretty sure I'm covered using that, but I've stopped using anything but Potassium this season on my big tree that I'm trying to keep from getting bigger. I searched the forum for a good while, but I couldn't find any specific info. Does anybody have any recommendations on how, how much, and when to apply both/either?

Side question, I heard somewhere awhile ago that egg shells are a good soil amendment for calcium because the egg shells breakdown slowly. Is that true? I've been composting kitchen waste and there's A LOT of egg shells in it (along with plenty of used coffee grounds); I'm wondering if I can use it for a top dressing without supplying too much calcium.

[johnb51]

I hope Har and Alex will weigh in on this.

[Orkine]

True about the egg shells though don't know how easy it would be to get enough for a bid tree.
I believe pineislander shared some prep he did with new drywall scraps - see link below
(http://tropicalfruitforum.com/index.php?topic=41725.msg411213#msg411213)

More likely you will get gypsum - your calcium - this way.

[Mark in Texas]

I  think some folks over think this stuff.  Without a tissue analysis you're throwing stuff at them hoping something sticks.  I read my trees and go from there.  Eggshells is not a practical source for Ca.  For starts the shells need acidic soil/water to break down.

Having said that I throw some gypsum around my trees when I think of it.  But 80% of their water comes from rainwater too.  I water with well water once in a while thinking the ultra high bicarbs of Mg and Ca plus some sulfates in it can only help with nutrition.   You have to consider how much Ca is in your soil and water source and whether or not it's in a soluble form available for uptake. 

I religiously give my faves Solubor about a month before they bloom.  Very little too as boron can quickly become toxic.  Most quality foods include boron also.

[johnb51]

Does the boron help the tree take up the calcium?  So if you use granulated gypsum, maybe you could dust it with Borax before scattering it around your trees at the drip line?

[Mark in Texas]

Does the boron help the tree take up the calcium?  So if you use granulated gypsum, maybe you could dust it with Borax before scattering it around your trees at the drip line?

No, aids in flowering and I assume fruit set. It's nutritional requirement albeit in trace amounts.   Our grape specialist recommended I blast the vineyard with Solubor early spring.  https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/boron-on-plants.htm

Borax should be fine.  BTW the drip line drill paradigm is meh..... I have found 1" oak roots with my tractor's subsoiler 50' away from the tree's drip line.  Of course they were old trees but over time that drip line goes quite far out on most trees.

[Seanny]

[Mark in Texas]

OK, now take 3 long steps from that point, jab a shovel or such a foot down and tell me what you find. 

[roblack]

OK, now take 3 long steps from that point, jab a shovel or such a foot down and tell me what you find.

limestone! usually hit it at about 3 inches. roots too.

[palmcity]

Does the boron help the tree take up the calcium?  So if you use granulated gypsum, maybe you could dust it with Borax before scattering it around your trees at the drip line?

No, aids in flowering and I assume fruit set. It's nutritional requirement albeit in trace amounts.   Our grape specialist recommended I blast the vineyard with Solubor early spring.  https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/boron-on-plants.htm

Borax should be fine.  BTW the drip line drill paradigm is meh..... I have found 1" oak roots with my tractor's subsoiler 50' away from the tree's drip line.  Of course they were old trees but over time that drip line goes quite far out on most trees.

I have to 10ft up you on that 50ft... lol... A row of oaks near my trees have roots 20 yards from their drip line. It is very easy to tell in the summer as the oaks take every bid of water and kill all the grass above them from the trunk to drip line and then 20 yards further... I do my best to deter them their roots... lol.

[Mark in Texas]

I have to 10ft up you on that 50ft... lol... A row of oaks near my trees have roots 20 yards from their drip line. It is very easy to tell in the summer as the oaks take every bid of water and kill all the grass above them from the trunk to drip line and then 20 yards further... I do my best to deter them their roots... lol.

I hear ya.  At least you folks get plenty of rain especially during hurricane season.  We haven't had a good rain in over a month.  BUT, we never had a summer either with highs in the mid to upper 80's until recently.  Normal highs are around 100F.

[JakeFruit]

The soil analysis challenge for many of us here in South Florida is the first few inches/feet is going to be fill dirt that was brought in to bring the lot up, an unknown depth below that will be whatever has accumulated since Florida arose from the shallow ocean (many) millions of years ago, and below that is going to be the sand and limestone base. I'd realistically have to do multiple tests to get a good idea of what I'm sitting on. I watched the dozen or so dump truck loads of fill come in to bring my lot up. Some fill was grey/black sandy topsoil, other amounts were orangey-reddish-brown with hard clumps, and still other loads contained some amount of limestone/shell/sand.

Throwing a safe amount of calcium/boron at my trees to see what effect it has might seem reckless, but with the amount of rain I receive here, I doubt there's much long-term risk to their health.

[ben mango]

Oyster shell powder is something you can buy in bulk from garden supply stores for a Ca source