quantity/method of gypsum application

[Zafra]

Just bought the property next to ours and inherited 2 mature mango trees in full flower! I'd like to experiment with gypsum but have no idea what would be the minimum amount to apply that could possibly be effective (gypsum is not cheap here like in the US so we can't just go willy-nilly), or how to apply it. Did a search but haven't found the info yet. Can someone point me in the right direction please? Thanks!

[Zafra]

No one? This is usually a pretty hot topic I thought. If the info is already posted somewhere if you could just give me a link!

[pineislander]

50 lbs per tree sprinkled under the drip line wouldn't be too much for a mature tree. It generally dissolves into calcium and sulphur.

[Zafra]

Aha! Thank you! So you just sprinkle around the drip line you don't have to dig it in at all? Also, would half that amount still have a chance of being effective or would that be a don't bother if you're going to use so little situation?

[pineislander]

I suppose any might be better than nothing. The effectiveness would really be seen if your soil is low in calcium. Any idea what soil you have? Acid, sweet, or neutral?

[markinnaples]

Mango: Calcium – a key for good Mango yield and quality
Calcium is increasingly recognised as a key to mango production in the Northern Territory for both yield and quality. Observation on yields indicates some of the low yields and fruit drop problems may be the result of low calcium levels and we are becoming more convinced that calcium is essential for good quality, particularly good skin colour. The evidence at the moment is only by observation. Recent research from Africa indicates that mangoes use a lot of calcium – 10 times that of phosphorus and magnesium.
Leading growers in North Queensland have long recognised the importance of calcium. Research by DPIF in the Northern Territory has indicated that growers’ opinion that calcium is important is possibly correct. Most Northern Territory soils including Katherine are very low in calcium – around one quarter of recommended levels. Soil levels should be at least 1000 ppm; most Northern Territory soils are only 250-300ppm.
Not only is the amount of calcium important but the ratio of calcium to magnesium. This should be at least 5:1 calcium to magnesium (expressed as meq/100g) The quality reports have shown the best coloured fruit come from orchards high in calcium, low in magnesium. Unfortunately many Top End soils including Katherine have ratios less than 2:1 (expressed as meq/100g).
Magnesium is present in many Northern Territory water supplies and for mangoes this is a problem. It makes fruit green and soft. The amount of calcium and magnesium in water supplies is variable so soil testing is crucial to get levels right. Test your soils to ensure you have at least 1000ppm calcium and your calcium:magnesium ratio is at least 5:1. NTHA provide a free interpretation service to members.
Calcium can be applied as lime, gypsum or dolomite. Dolomite generally is not recommended for mangoes as it is high in magnesium. Lime is used to increase pH and gypsum is used to increase calcium where pH is OK or high. Foliar sprays of calcium around flowering and fruit set have also been used to improve yield and quality. Current indications are that calcium should be applied at flowering (soil and foliar), after harvest (optional), and especially at the end of the wet season after the heavy rains to set the tree up for good calcium levels before flowering.
The amounts of lime or gypsum required on most Top End soils are large. The recommendations to date have generally been too low. They fail to take into account wet season leaching and the negative effects of high magnesium in most irrigation water. Mangoes appear to use a lot of calcium. Most growers have taken 2-3 years to get their calcium levels and their calcium:magnesium ratio right. Applications of 20kg/tree, three times a year for 2-3 years are not uncommon so get your soil tested. Leaf analysis can be used as a guide but can be misleading as calcium increases naturally as leaves age. It is important to realise that other elements also have to be corrected to get the maximum benefit.
Boron is essential for the best calcium response and should be applied at up to 50gms per mature tree. It is also important to have phosphorus, zinc and potassium levels right. The bottom line is get your soil tested. The best time to test soil (in Northern Territory) is December to February before the main time for application in March.
Note from Sheryl:
Refer previous newsletters on talks by Peter Young and Robert Pulverenti
Robert says to only put on 5g per m2 per canopy and water in very well.
Authored by:
Ian Baker
http://stfc.org.au/mango-calcium-%E2%80%93-a-key-for-good-mango-yield-and-quality

[Zafra]

Great info thanks so much! 

[Seanny]

50 lbs is $40 here. Not many people dump that much on a tree here.
Fertilizer is cheaper.

[pineislander]

You can get gypsum free if you are diligent and get together with a builder who is doing drywall work. Only use USA made gypsum and only use scrap from new construction. They typically have 100's of pounds when they put the wall board up, and usually give it away if you ask nicely.

[Guanabanus]

That is a really interesting opinion about Magnesium!

[SeaWalnut]

50 lbs is $40 here. Not many people dump that much on a tree here.
Fertilizer is cheaper.

Gypsum from constructions should be dirt cheap.Here costs @2-3dollars per 40 pounds a bag.
And its the reactive type from a bag not from demolitions.
If you want to get gypsum from demolition ( plaster walls) ,i think people would actually pay you to get them rid of it.
The price of gypsum its cheaper than the price of the cheapest portland cement per bag.

Gypsum dilutes 1:400 parts of water and if you dont have enough water then you wont get enough gypsum into the soil.
I like that it bonds the nitrogen from manure and natural fertilisers and fixes it as nitrogen sulphate ( but again it needs a lot of water to be able to do this).
It also helps to flush the salt build up in a pot and this is also dependent on the water intake since the water flushes the salts not the gypsum.

Weathered red soils like those in Australia that are mentioned ,are soo poore in calcium because they are the oldest soils on Earth.
They got a lot of rain that disolved all the calcium and carryed it away.
Also ,rainforest soils wich are red too( from iron) are lacking calcium too because of too much rain.

[Seanny]

I paid $14 for 40 lb for gypsum in the garden area.
Gypsum in the other area of the store was expensive.

[SeaWalnut]

I paid $14 for 40 lb for gypsum in the garden area.
Gypsum in the other area of the store was expensive.

Those garden gypsum pebbles for garden are 10 times more expensive here and they come from demolition or as waste .
Just buy regular construction gypsum from the plaster section.
Usually there are 2 types,one with delayed hardening wich has an aditive added to it.
You want the cheapest ,fastest hardening plaster gypsum.
Add thin layers under the mulch in a place where water can wash it away( rain falls on it and where you pour water and fertiliser,manure,etc).

[EddieF]

I never used gypsum & have sad mango production from my 20yr old pruned tree.  This why?
10lbs for a 1' diameter trunk & 20' canopy tree sound good?  Typical south fl sandy soil.
Btw- anthracnose back.  Gypsum help prevent it?
Ed

[SeaWalnut]

I never used gypsum & have sad mango production from my 20yr old pruned tree.  This why?
10lbs for a 1' diameter trunk & 20' canopy tree sound good?  Typical south fl sandy soil.
Btw- anthracnose back.  Gypsum help prevent it?
Ed

Gypsum act as an antifungic too but mild.
Its because of the sulphur in it.Sulphur is an antifungic used in the vineyards.Thats why people complained it killed their mycorrhiza.

[Guanabanus]

I don't do "dripline fertilizing."

I fertilize "twice the radius of the canopy" (a.k.a. "1 1/2 times the diameter of the canopy"), "wide and thin".

This means the entire area under the canopy (except a foot or two near the trunk), the drip ring, and a greater area outside of the drip ring.
[You pace from the trunk to under the tip of the longest horizontal branch (before pruning), and continue pacing in a straight line, repeating the number of paces that you did under the canopy, and make a complete circle from there.]  In a mature grove at normal spacing, such as 18' x 20', one fertilizes the entire grove floor.

One opens ones fingers as one tosses, in a bowling motion, so that the fertilizer falls sparsely on the soil--- one has to look closely to see it.  On sandy soils, I put out a relatively large amount of partially-slow-release fertilizer, Spring and Fall.  Because of the "thinness" of fertilizer landing in any one spot, and because I usually apply granular Gypsum at the same time, I avoid root-burn, leaf-burn, imbalances, and other deleterious effects.

Persons who put down, even much less fertilizer than I do, but in an intense amount in small areas--- such as in "The Dumb Ring" near the trunk, or a narrow "dripline ring"--- do kill hair roots, earthworms, and so on.  The canopy probably won't show any damage--- because dead roots don't send up too much fertilizer.
And despite having been "fertilized", the tree continues to generate all the same complaints.

[Guanabanus]

On sandy soils, for maintenance:

For each 50-lb. bag of 8-2-12 or 8-3-12 (or 8-3-9), I put out at least 1/4 of a 50-lb. bag of mini-prilled Gypsum (coarse granular works too).

For each 50-lb. bag of 0-3-16, at least 1/3 of a 50-lb. bag of Gypsum.

For each 50-lb. bag of 0-0-22 "K-mag", at least 1/2 of a 50-lb. bag of Gypsum.  And so on.

During the first 2-3 years, two or three times this amount can be usefully corrective, in cases of obvious deficiency.  One must not try to "correct a soil" all at once.

[The third number in fertilizer number names is Potassium.]

Available in the "soil solution", easy for the plant to absorb, one wants to always have more Calcium than Potassium or Magnesium;  otherwise, imbalance occurs, which may even be visible as fertilizer burn on the leaves.

[Cookie Monster]

I found a chest spreader to be helpful. Earthway makes a 40 pound unit (nearly a full bag of fertilizer). It's a little tricky to connected and a little messy (and admittedly overpriced), but it makes quick work of spreading several hundred pounds of fertilizer.

https://www.amazon.com/Ev-N-Spred-Earthway-3100-Broadcast-Spreader/dp/B00002NCA4/