The Tropical Fruit Forum

  "Furthermore, according to the Puyallup Research and Extension Center at Washington State University, gypsum negatively affects the mycorrhizae that enhance root health and development"

Any opinions?

here is the reference from Payallup, which has no reference.
https://s3.wp.wsu.edu/uploads/sites/403/2015/03/gypsum.pdf

I checked and found a reference, with peanuts which were drenched with gypsum at planting.
https://www.nrcresearchpress.com/doi/abs/10.1139/b85-232?journalCode=cjb1#.XkCLMTJKjb0

I also found a reference in which nitrogen fixing in a soil deficient in calcium was substantially enhanced with gypsum.
https://link.springer.com/article/10.1007/BF00213437

I can't really comment on your greenhouse experience but most Ambarella I see here in Florida and those I've seen in the Caribbean are not pretty, they are prone to skin defects as seen in this video:
https://www.youtube.com/watch?v=uqAvNUgzyPU

They still ripen OK and many just suck the juicy flesh not really eating the skin. Many just use the green fruit in pickles, etc.

I should add that in habitat it enjoys alkaline soil even doing well on heavy high pH caliche soils.

When I lived in the Caribbean this was an extremely common tree all over. I didn't know about the dioecious nature at the time but it was clear enough that many never bore fruit & I assume they were males. Even some females would become biannual bearers loading up heavy then taking time off. The heavy bearers would be severely beaten with sticks by folks getting fruit except by vendors who wanted whole clusters to sell, they would send climbers up to get huge quantities.

Florida soils are geologically lacking sufficient essential nutrients in the soil profile for some crops.Their for outside outside sources are required whether synthetic or organic. I'm all for improving soil ,but rhizosphere can't supply what's not in the geology of the soil if you believe other that's religion!

Some years ago I was looking at how the Amazon gets many minerals from Sahara dust and I know we see it too.
Otherwise, especially here along the coast, we do get a good dose of sea minerals which must be helping us without even trying. I notice that the Advancing Eco Agriculture folks do not use synthetic fertilizers yet produce and sell sea mineral kelp and crab/shrimp/fish products. Studies of Tampa Bay found that nearly 50% of the nitrogen entering the bay came from wet and dry atmospheric deposition, and ran into the thousands of tons nitrogen per year, some from natural sources some from manmade pollution, fires, lightning, ocean and dust. Interesting fact these constitute a hand-off foliar feed and then fall to our soils.

What do you think of alfaalfa?

So far as I know alfalfa isn't adapted to tropical climates or the light soils and high water tables we get in south Florida.
It has been grown but more of an annual. We do, however have a huge variety of possible annual and perennial legumes of all statures including trees so there isn't a shortage of nitrogen fixers.

I once winter-sowed white dutch clover and rye grass intensively across a 2 acre garden plot. In spring I tilled raised garden beds leaving the clover in paths. It worked well but two disadvantages I found:
1. The clover was damned slippery and especially in spring when the dew was on it in the mornings.
2. It held dew/water underneath so long into the day it became very difficult to mow, the stems were very succulent so that the mower would clog up with wet clover and was so slippery the wheels of the riding mower would slip.

Lake Erie was in far worse condition almost dead in the 1950's and phosphorus reduction began to bring it back. then invasisve Zebra and Quagga mussels came into the system.
The original food web was:
sunlight → phytoplankton → zooplankton → fish
the change was towards:
sunlight → phytoplankton → dreissenids → fish
Previous dominant phytoplankton algae was nitrogen fixing but has moved towards blooms of mycrocystis which doesn't fix nitrogen.
The molluscs filter water increasing light for photosynthesis and also graze hard surfaces opening up attachment points for filamentous mussels. However, the molluscs also excrete both nitrogen and phosphorus introducting new complexities into the system.

Would growing sweet potatoes before I plant the trees help build up the soil? As well as adding other amendments such as worm castings, biochar, azemite, and mulch. Thanks!

Sweet potatoes will grow on fairly poor soil and like sand but don't really build up soil, and removing the harvest removes nutrients from the soil. They do make a good ground cover but I had some potatoes form around the roots of newly planted fruit trees and had to dig deep into the root ball to get them out.
One easy thing you could plant under new trees are ordinary raw peanuts, not to eat because you have to dig them out but just as a ground cover they like sandy soil and they should generate some nitrogen. I've had some last a year plus. Plant a shelled peeanut every six inches and cover with some mulch they can push through very easily.

This fish could have saved the Great Barrier Reef wich in turn could have saved the whole planet from global warming.
Because stony corals skeleton are a carbon sink ( calcium carbonate).
A dead GBR its like having a dead Amazon forest and it died because of human ignorance not even for profit or to benefit the civilisation.

The premise that the Great Barrier reef is dead is wrong.
2017 explanation:

https://www.youtube.com/watch?v=bcjaQYcsr-w

3 months ago, from Australian Broadcasting News in-depth:

"Bottom line is the reef is not dying, there are some parts of the reef which are degraded but there are other parts which are absolutely magnificent"

https://www.youtube.com/watch?v=Qqqs7kxHbw0

If you have rock it needs special treatment but since this is a house lot you may have some unusual fill dirt maybe even fill rock. Some places add fill which is special stuff which compacts for a stable foundation and may include some clay. I am building and they use this under the foundation plus compacted it with a 19 ton vibrating 'steam roller' which packed it very tight. You need to get a post hole digger and go down about 2 feet to actually see your soil profile. You might ask around folks who were there when houses were built and check who has had success to emulate what they did. Just because one tree died doesn't mean it was a soil problem, could have been aftercare or even drainage issues.
On a house lot a mixture of uncut grasses and weeds may not be easy to achieve.

Organics are great and I use them plus a diversity of companion pants and legumes but I highly recommend starting with a full slow release total fertilizer with micronutrients. The one I use is called Nutricote Total.
I put a double handful directly in the hole before planting. DO NOT do this with ordinary fertilizer. However, this one is 100% slow release and lasts through the rainy season for six months. I think the benefit is that the fertilizer is directly under the roots and slowly released with no chance of washout or burning. I have planted seeds directly on top of a spoonful of this fert, it does not burn. It is very popular with the nursery trade. I do not see permanent harm using synthetic fertilizer and have observed good soil microbiology and legume nodulation on soil which has had this fertilizer added.Best of all I have never had any nutrient deficiency symptoms

https://www.arysta-na.com/Nutricote/files/NUT_18-6-8_PIS.pdf

Oh god, I thought they would eat just insects.

They are herbivores.

38 bokeelia  that used to be a every year temp.my 30 foot+ rollinia did not care for that wind.Well I can see the fruit now!

Interesting I am just a mile or so north and didn't get a temp reading but the wind may have helped. I don't see signs of leaf damage defoliation on breadfruit will check again today.