Green sand is an extremely weak mineral that turns to clay particles quite easily.

The soil could probably use some well composted material to break up the clay rather than more mineral components...especially if you're tilling it in, which will effect the soil structure quite quickly.

The fast acting gypsum is just more highly water soluble. While this reaction with water takes place it does release heat via chemical reaction, but in a soil it's generally not worth considering.

As far as it's effect on microbes...breaking up the heavy clay soil to let oxygen into the soil profile will be of more benefit to microbes over time than any amendment breaking up the soil. Microbes (beneficial ones) are generally found in well oxygenated as well as moist soils.

I have actually applied over 50 yards of leafgrow topsoil mix. I know that feeling will the microbial Network and as far as the green saying goes I only applied lightly to help the microbeswith the trace minerals contained within the the green sand. also the soil ph remains around 5.5 - 6 no matter what I do.

I meant *tilling not ^feeling. And *5Cu.Yrds. not ^50. Thanks for the/any help.

Where in the United States are you? Zone 6a tells us nothing except which plants might survive a normal winter where you are and the United States covers a very wide range of soil types and weather.
Where Gypsum might help is in sodic clay soils in arid areas of the southwest. Vermiculite, unless applied in ton quantities, will not help much with compacted clay, nor will "topsoil" unless added in very large quantities, as well.
Organic matter, however, will change compacted clay soils if about 6 to 8 percent is incorporated into that soil, not overnight but over time.

Here is a link that might be useful: fixing compacted clay soils

Maryland. Leafgrow is the organic matter I added in a 50 50 mix with top soil. I am aware of good ways to loosen clay soils. My main question though, is will soil microbes be harmed by fast acting gypsum?

I am aware of good ways to loosen clay soils

Apparently you are not if you think gypsum is going to be of benefit. The primary recommendation endorsed by soil scientists across the globe to loosen or lighten clay soils is the addition of sufficient quantities of organic matter. Period. End of discussion. Not gypsum, not vermiculite, not sand.

Virtually anything not organic in nature that is applied in excess (and even a few organic products) can harm soil biology. Gypsum is known to have an adverse affect on mycorrhizal populations.

Here is a link that might be useful: Myth of gypsum as a soil conditioner

Will it harm soil microorganisms? If used in rational amounts, no.

Will it help with the hard clay soil? If he soil is sodic, it may help some. If it is not sodic, then most likely not.

Vermiculite, sand, gravel, etc, won't do much of anything until, the volume fraction approaches or exceeds that of the clay.

You might want to get the truth about what gypsum does and does not do, as well as some commentary on its overuse. It won't hurt soil organisms at all, but you might well be applying it for nothing.

Here is a link that might be useful: The Myth of Gypsum Magic, Washington State Extension

Thanks MulchMama. That was most helpfull.

my experience is that gypsum does no harm to microbes or worms etc.,. if you have the type of clay that could use some help in our case volcanic red stuff covered with red or brown clayey loam it will help, we literally dig it in and then mulch heavily.

we've had native shrubs (noted for being slow to settle and grow) go from tube stock to over 1 meter in 12 to 18 months.

anyhow i'm not a knocker of something that helps in the right circumstances, you really do have a major hate program against relatively inexpensive gypsum, maybe self interest at work?

simple test take a dessert spoon ball of your clay(gypsum does no good in sand) place it in a glass jar covering it with water, if in around 24 hours the clay is dissolving then gypsum will help. the knockers always cry out like chicken little's 'the sky is falling' but they offer no real tried themselves advice.

if you bought a bag of good quality gypsum(key0 and it worked good and well if it didn't no major loss and no damage.

len

Here is a link that might be useful: lens garden page

Oh geeze, I didn't click Gardengal's link before I posted the same one. Anyway, she is absolutely correct, and no one has a vested interest in a hate program against a mineral so highly toputed as a soil amendment.

Again, I apologize for the duplicate link.

Dispersing clay particles doesn't mean it's doing good things for the soil. High sodium will accomplish this...for instance. While gypsum is more inert to soil than sodium, it still adds very little to the soil...it just chemically separates aggregates, and it's effect is temporary and not always positive. It's a "quick fix" that doesn't "fix" much over the long haul.

Clay particles complexing with organic matter (which provides access to beneficial complexed metals, especially) is a great way to break up heavy clays while providing plant benefit. The organic acids along with the acids most agriculture plant roots exude make nutrient gathering by the plant more area specific rather than simply relying on what's available in the soil solution. The increased ease of roots being able to move in the soil makes it easier for plants to grow and contact these areas.

Rather than trying to turn your soil into a "soil solution" broken up by chemicals dependent upon soil moisture for heavy clay issues, you should attempt to make additions to a soil that will provide both improved/loose structure as well as improving the soil's nutrient holding/exchanging capabilities. Dispersing aggregates of soil isn't always the best solution to the problem. You still end up with the same soil, just a chemically dispersed soil solution that is generally temporary. OM additions are not permanent, but they are a whole lot healthier in the short + long run and easy to maintain over time with top dressing or residue return.

Gypsum has a place (specifically high clay or high sodium soils (gypsum drives sodium out of soils because it competes easier for exchange sites in clays and leeches the sodium out)), but it is not a long-term solution for soil structure. It is a temporary chemical "fix." It should not be used as a sole solution...it's best used in conjunction with other amendment solutions (OM, specifically) where applicable. It simply does not persist in effect in the soil because of it's chemical nature and what it's actually doing to the soil. It is not a soil building mineral...it is not organic matter...it does not persist for a long time.

Also, don't be upset because I'm referring to gypsum as a "chemical fix" even though it's an organic substance. It's effect on the soil is purely that of a chemical...simple as that. It does not add to soil structure, it's effect is neither permanent nor long term, and it effects nutrient competition and availability in certain soil types, especially dependent upon native nutrient content and pH. When you add gypsum to a soil you are effecting nutrient exchange plus soil aggregate stability, and it's all quite temporary. It can help OM and larger mineral particles find it's way in between broken up clays/silts in the short run, but if no additional amendments are made it will eventually turn right back into the clay/silt it was to begin with.

This...

Those of us that advise against using gypsum are not waging a hate campaign and do not have a vested interest in anything except good, sound gardening practices. If a product has little to no benefit to the soil why spend your money on it? Gypsum has little to no benefit to most soils so the only people that would benefit from its use are those that sell it.

I read the question, and I wonder what it really is. Compaction? Slow drainage? or just a fundamental misunderstanding of the nature of different soils?

I'll always opt for the third. I've been involved in two projects over the last eight months that have taught me that even being a credentialed soil scientist does not preclude one from being an idiot on the subject. It was a very expensive lesson.

So you have heavy clay soil, and you say you tilled.

Is there an alternative definition of tilling I am unaware of? Or a methodology you call tilling I'd call something else? like scratching the surface using a tiller?

Adding kelp and greensand didn't do much. Shocking. Adding fertilizer components did nothing to change a structural (not exactly the right word, but close enough for the purposes of this conversation) property. Shocking, I say. Which begets the observation...

So you have clay soil. with a pH of 5.5-6. I'd suggest that rather than focusing on soil microbiology, you learn a little bit about soil chemistry, and by extension, fertility. If you have a clay soil with a moderately low pH, you may be surprised at the need for additional fertilizer.

One question...how old is the construction? New house? or has it been there for a few decades?