Gypsum vs Lime

I recently read a book at the local library that said Gypsum was better for adding calcium to soil which is needed to fix nitrogen. If I find my notes from that day I'll add them and the source reference here, but despite my best efforts, I've misplaced them. In substitute, here are links with a summary of the same info.

Difference Between Gypsum and Lime
http://www.calciumproducts.com/component/k2/item/201-difference-between-lime-gypsum

Calcium and Nitrogen Fixation
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1086420/

Ryan, you posted this approximately a year ago, so I don't know whether you got all the info about this topic that you needed.  I thought I'd mention something about my own use of gypsum in preference to lime.

I'm on some acres in what was, until the mid 1950s, part of a tract of mixed forest, mainly coniferous.  The land's soil pH while it's still in forest is on the acidic side, but this many decades later everywhere I've tested soil in my clearing the pH it's very near neutral — between 6.8 & 7.2.  That is fine for many cultivars, but it's not acid enough for potatoes (for instance) and definitely way too alkaline for blueberries, and I did want a modest patch of those.

I knew that calcium would be required for good crop returns, but also knew that lime would alkalinize the soil.  So when I've applied calcium it's been in the form of gypsum.  And, for instance, this worked out to allow my nursery-bought blueberry plants a favorable transplanting.  (I dug holes, mixed original soil with compost, sphagnum peat, gypsum, a bit of alfalfa meal for nitrogen.)  The plants got a good start and then the soil environment in the patch, which I covered with fine (wood) planer shavings & sawdust, promoted the natural establishment of fungal mycelia.  And now for years the need for nitrogen input seems very little.

Just an example that leapt to mind for me.

To my knowledge, the gypsum on the market is mined in China. Not a sustainable choice if you don't live where there's a local source, even if it's actually good for the soil, which I'm not sure about. Gypsum mining is pretty destructive from what I remember. Now don't be throwing your eggshells in the garbage if you wanna add calcium to the soil.

Sarah Koster wrote:To my knowledge, the gypsum on the market is mined in China. Not a sustainable choice if you don't live where there's a local source, even if it's actually good for the soil, which I'm not sure about. Gypsum mining is pretty destructive from what I remember. Now don't be throwing your eggshells in the garbage if you wanna add calcium to the soil.

Here's a link to a page concerning eight companies operating in Canada and mining gypsum.
https://www.manta.com/world/North+America/Canada/gypsum_mining--E31F308G/

As I was posting from my position within the Canadian context, I wanted to say that not all North American gypsum is imported from China.  But I'm no blind 'patriotic' nationalist, so I won't vouch for the sustainability or environmental consciousness & caution of those eight companies.  Canada's regulations and scrutiny, though, are generally acknowledged to be better than those of China (attributable to the latter's ultra-rapid-development penchant).

I’ve heard of using drywall scraps for gypsum. Not sure if there are harmful ingredients or not. Hopefully someone on here knows?

Ken W Wilson wrote:I’ve heard of using drywall scraps for gypsum. Not sure if there are harmful ingredients or not. Hopefully someone on here knows?

I was just telling my father as we took all the drywall out of an old house I have, how stupid it seems to throw drywall away, yet buy tons of lime every year to put on my land to grow crops. (The soil is VERY acidic here in Maine).

The lime I do buy, which is called Mill Lime, comes from a local paper mill, and is a recyled material so at least it gets a second life. It also is a lot cheaper since I am just paying for the trucking from paper mill to my farm ($22 a ton instead of $110 a ton for mined lime). It also is stronger in increasing the PH levels in soil, but lacks the magnesium mined lime has. For instance, if a soil test calls for 1 ton of lime to the acre, I can apply .8 of a ton of mill lime. It is also faster acting, sweetening the soil in 3 months instead of 6 months for mined lime, but lasts 4 years instead of 7 year like mined lime.

Another alternative to expensive milled lime for me anyway, is AlgeaFiber which is a seaweed product. It comes from a company that makes food grade carrigean that is used in everything from Jell-O to toothpaste. It is organic stuff, and used to be free, but now costs $1.90 a ton. That sounds like a bargain, and it is, but it is NOT a 1 for 1 deal. In fact its potency for lime is very low. If my soil report calls for 1 ton of lime to the acre, I have to apply 10 tons to the acre to get the equivalent of 1 ton of milled lime!!

That is too much!

On grass ground like pastures and hay fields, 10 tons to the acre would smoother the grass. That means it really is only effective on corn ground where the soil is tilled.

It does however have a lot of benefits beyond just sweetening the soil. It has a lot of the minor elements like copper that can really help get the crops to grow.

Ken W Wilson wrote:I’ve heard of using drywall scraps for gypsum. Not sure if there are harmful ingredients or not. Hopefully someone on here knows?

The answer to this is: It depends on when the drywall board was made. Older (pre 1980) drywall was just gypsum with two layers of paper covering, today they have different papers, some with fire retardant, and they have moisture/ mold resistant.
Fortunately this information is usually printed on the edge tape so you can check to see if there are chemicals present.
If you do find gypsum board that has been treated, you can still use it in soil but you will want to burn it (heat treat) first and you will want to add a mushroom slurry to that soil either as you incorporate the gypsum board bits or after.
If you do heat treat gypsum board you will find that it more resembles milled lime in that it won't take a long time to change the pH of the soil and it will tend to not last as long as just ground up gypsum board.

Redhawk