Research showed that calcium chloride and calcium thiosulfate applied through a center pivot improved yield, calcium in the seed, and germination.

However, these products do not increase the soil-test calcium levels after harvest nearly as high as gypsum, so in that regard, they don’t replace gypsum, he says.

Calcium needs to get into the pegging zone because it has to be absorbed directly into the nut, says Harris. “There’s a direct correlation between calcium in the seed and germination, and you probably want to check this on any saved seed. In our rate study, the more calcium we had in the seed, the higher the germination.”

There are multiple sources of lime and gypsum, says Harris, so the selection process can become complicated. But there doesn’t seem to be any difference between the gypsum materials currently available, he says.

Last year, USG 500, PCSA Wetbulk, AgriCal and a new product called Gypsoil were tested and seem to perform equally. Selection can be based on factors such as product availability and how well the material handles, Harris says.

It is better to use gypsum for dryland peanuts, says Harris.

“During the past two years, gypsum at bloomtime has outperformed lime at planting as far as calcium to the pegging zone. This makes sense since the calcium in lime is less soluble than the calcium in gypsum under limited water situations such as in dryland production.”

Also, it has become clear, says Harris, that foliar calcium applications are not recommended on peanuts. “At 1 quart per acre, they do not provide enough calcium, and even if they did, they do not get translocated from the leaves to the developing pods.

“Putting liquid calcium through a center pivot is considered a soil application because you are putting out so much water per acre, that even though the water hits the leaves initially, the majority of it runs off and is basically applied to the soil.”

It is not recommended that growers apply gypsum at planting since there is always a chance that with enough rain or irrigation early on, the calcium in gypsum could leach below the pegging zone, says Harris. This is especially true on sandy soils.

“At this time, it’s not recommended to split gypsum applications and put some on at planting and some at early bloom, but research studies are being conducted to determine if there may be a benefit to this timing of applications.”

Gypsum should be applied at early bloom or approximately 30 to 45 days after planting depending on growing conditions.

“Once you get past 100 days after planting, the majority of pods probably have already absorbed the proper amount of calcium or they aren’t going to. Also, after 100 days after planting, running over lapped vines is not desirable.”

phollis@farmpress.com