Conditioning clay soils

Question ...

I am about to dig two new raised beds for growing vegetables. My soil is clay and, with previous beds, I have double dug, adding grit to the bottom of the second spit, manure/compost and gypsum, to help soil particles to bind together. However, I intend to grow potatoes in these new beds and would like to know if the gypsum will do any harm. I understand that it has some of the same effects as lime but does not alter the pH. I would not normally use lime with potatoes for fear of increasing scab, but will the use of gypsum still cause this problem?

Answer ...

Gypsum is quite suitable to use to condition heavy alkaline clay soils. It should not affect the soil pH, so should not cause problems for your potatoes. Add 250-500g per sq.m. We also recommend you have a soil pH test before adding gypsum. Testing kits can be bought at garden centres.

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