A variety of gypsum sources and application methods gives producers options.
By Amanda Huber
Gypsum, or calcium sulfate, products are available from many sources and can be purchased based on price, availability and spreadability. It used to only be available in the granular form mined out of Canada or a by-product of fertilizer mining in Florida. Now, there are “wet bulk” products scrubbed from smoke stacks and another created from citric acid production.
No matter the source, at least 1,000 pounds of gypsum per acre works on today’s varities, says Glen Harris, University of Georgia Extension soil specialist. Lime is still preferred if soil pH needs adjusting, but it must be put out prior to planting so that it has time to solubilize and move down into the pegging zone.
The calcium in gypsum is able to move more quickly through the soil profile, thus the reason it is applied at early bloom. Split applications, such as at planting and bloom, are still not recommended.
Wet-Bulk Application Tips
For producers making use of the “wet bulk” sources of gypsum, Harris says application takes a bit of know-how to accomplish.
“The use of a conveyor belt to load the material into the spreader will help to fluff it up,” he says. “Also, spread wet-bulk materials using a stainless steel, steep-sided spreader with a wide chain. Applicators should drive slowly when transporting and applying the material so that it does not pack down.”
Another trick is to stand a PVC pipe up in the back of the spreader by the gate and, when it is pulled out, the material should flow more easily.
The Choice For Dryland
Harris says producers should consider using gypsum in dryland production.
“Without irrigation to move lime down into the root zone, I am not sure it will get where it is needed soon enough. If there have not been enough rain events, adequate calcium may not be available,” he says. “Dryland producers should consider using only gypsum.”
For gypsum, apply at bloom, but Harris considers 100 days as too late.
Overall, it is the source that determines timing and rate, but adequate calcium is needed to reduce “pops,” lessen the likelihood of pod rot and black heart and to increase germination the next year.