Gypsum and Rain

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Question from Roy: 

What’s the word for land plaster leaching? If I applied land plaster then got a heavy rain within 24 hours, would I need to make an adjustment? Not that this could happen this year!

Answer:

This is a hard question to answer. If the peanuts are relatively old and large, a heavy rainfall event will not be a disaster. Peanuts that are about 12 inches wide or so will probably be okay because soil washing will be limited because the peanut plant softens the impact of the rain. If the peanuts are say 6 inches or less and the gypsum is out I suspect much of the soil that had the gypsum in place also washed to the middles. The rainfall we are having right now is excessive in some places, and this is not typical. We recommend gypsum in late June into July because we want peanuts to get big enough to keep soil and gypsum from washing if we happen to get big rains in early to mid-June. Honestly, we don’t have data to address this issue (heavy rain.) So, if you have small peanuts (8 inches wide or less) and you received 4 or more inches of rain, especially in one event, I would encourage growers to apply half the normal rate after we get through this wet period. If you have peanuts that are fairly large (greater than 8 inch diameter when the gypsum was applied) with modest rain, I would not do anything. They should be okay. If you have growers that were already wet and received high amounts (I talked with someone who received 7 inches over the weekend) and have already applied gypsum, I would apply ½ the normal use rate when peanuts get bigger and fields dry out.

Article first appeared as North Carolina Peanut Note (PNNC-2013-035)