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Soil Amendments - Do I need to use gypsum?

by Marika
(Cyprus)

Question:


I've heard that I need to use gypsum for lawn care. I'm not sure why and how should I use it, and I can't even find a good source for it. Is it a myth or something that is really needed for getting a lush green lawn?

Good question! Thank you Marika.

ANSWER:

Maybe...

The only way to really know is to have your soil tested. The results will tell you what soil amendments need to be added and how much you should apply. I recommend that you have your soil tested at least every 3 years. In the United States, we can send soil samples to our local research university, agricultural extension service or a private soil testing lab. Check with a local agriculture agent or garden center, they should have soil testing information.

Gypsum (calcium sulfate) has been hyped as a soil amendment that will improve drainage. It only works in clay soils that are high in sodium - saline -- or sodic soils. Sodium destroys the structure of soils - resulting in hard, compacted soils. Gypsum works by replacing the sodium (Na+) ions bound to soil particles with calcium (Ca++) ions. The sodium is then flushed out of the soil.

Here in the United States, sodic soils are common in the arid West and some coastal areas. When you say "I've heard that I need to use gypsum" - and if you are hearing this from local gardening experts -- you likely have sodic soils. Again, the only way to know for sure is having your soil tested.

Sandy soils will also benefit from the calcium and sulfur in gypsum -- it is a good source of these nutrients and sandy soils tend to be calcium and sulfur deficient.

Where to get gypsum? Check with your local agricultural cooperative or garden center. They should have gypsum for lawns and gardens if it is commonly used in your area.

If your soil does have a salt problem, consider planting a species that is salt tolerant. Seashore paspalum is a very interesting warm-season grass that is being used on golf courses in coastal areas. On some sites, it is actually irrigated with seawater.



Tips for using gypsum:

  • Gypsum is going to be most effective when added before planting and tilling it into the top 6 inches.

  • On established lawns - aerating with a core aerator before you apply soil amendments helps incorporate materials into the soil.


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