This is what I found:
"When blossoms appear on the peanut plants, apply Gypsum [calcium (CaSO4) sulphate] in a 14-inch band over the plants (does not burn) at the rate of 15 lbs. per 1,000 square feet. This is essential to the formation of the peanut kernels."
HTH

Here is a link that might be useful: Growing peanuts

I used to successfully grow peanuts in my garden several years ago but never heard of dusting with gypsum. I'm sure they need calcium as do many other vegetable plants. I mix dolomitic lime with my comercial fertilizers when planting most everything.