Peanuts: Time For Calcium

Former UGA Peanut Agronomist Dr. John Baldwin always said, “If it don’t rain, it don’t matter.” We are putting out landplaster in peanuts now to supplement calcium. If we don’t have enough calcium, we get “pops”. This usually happens more in dryland fields as we also need water to move the Ca through the roots. Peanut plants absorb calcium through the roots (and transported upward in xylem) and not translocated through the leaves. Once peanuts begin to peg, the peg and developing pod passively absorb Ca directly from the soil. This is why we need high levels of Ca in the pegging zone. Ca must be available in a water soluble form and is why gypsum or landplaster is recommended to apply at early flowering. We also need rain very bad. Thankfully, we are getting some today.

UGA Fertility Specialist Dr. Glen Harris has more to say about different types of Ca:

“The more they stay the same! When we switched from growing small-seeded Georgia Green to large-seeded Georgia 06G we really thought we would need to increase our gypsum or calcium recommendations. But after years of research we concluded that the recommendations didn’t need to change. You can still use a pegging soil sample (3 inches deep, next to the peanut row soon after emergence) if you have at least

1. 500 lb/a of soil test calcium AND
2. Calcium to potassium ratio is 3:1 or better

In this case, you don’t need to apply gypsum. If you do not meet EITHER of these requirements then you need to apply 1000 lb/a gypsum at early bloom.  Also, all peanuts grown for seed should automatically receive this gypsum application regardless of soil test calcium levels.

There are a number  of different gypsum or landplaster fertilizers currently available. Chemically they are all calcium sulfate, and the good news is that we have tested these too. They are all comparable as far as providing calcium to the pegging zone of a peanut. Probably the most commonly used is technically called Flue Gas Desulfurized or FGD gypsum and is a byproduct of scrbbing sulfur gas out of smokestacks at coal burning power plants. I call this “smokestack” gypsum although a lot of growers refer to it as “synethetic” gypsum. There is also the old ‘wet bulk” phosphogypsum (a by-product of the phosphorous fertilizer production), and the naturally mined USG 500 among others.

The lime method can also be used to provide calcium to the pegging zone of peanut but a few things:

1. This method should only be used when you also need a soil pH adjustment, otherwise use gypsum if you need calcium.
2. Both dolomitic or calcitic lime can be used. Some people think you HAVE to use calcitic but this is not true.
3. The lime method does not work as well as gypsum under dryland conditions during years of normal rainfall. We have good replicated field data to support this too.

We have also been testing putting calcium chloride though the pivot at peak pod fill (60-90 days after planting). This method has a fit when you are on the borderline of needing some calcium. The benefits are you can apply this yourself and you do not have to run over the vines. One disadvantage compared to gypsum or lime is that this method with not build your soil test calcium levels basically at all.”