Gypsum Rate and Timing Peanut Notes No. 53 2018

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Gypsum is needed for Virginia market type peanut. See pages 27-29 in 2018 Peanut Information for detailed comments. There is an increasing tendency for growers to apply gypsum in early June to mid-June. This approach is understandable but one concern I have is if we receive a major rainfall event shortly after the material is applied. I prefer to see more foliage in the canopy so that less washing of soil and potentially gypsum into furrows occurs. A few years ago I presented information at production meetings showing that the frequency of heavy rainfall events seems to have increased over the past decade in the month of June. Delaying application of gypsum until the canopy has increased can be a buffer against having to make a difficult decision about applying more gypsum after a major rainfall event in early June has occurred. The answer is generally that one application as all I will make in a season and I will take my chances on enough gypsum being present for the crop. I have often recommended applying ½ the normal rate if rainfall exceeds 5 inches over a short period of time after the initial application. With some of the late planted peanut we will have in the state this year, there may be a tendency to apply gypsum to those peanut at the same time gypsum is applied to older and larger peanuts. Logistics most likely will drive this decision, but applying too early can leave peanuts vulnerable later in the season if rainfall is excessive soon after application. We are growing some runners in NC (5-10% of acreage) and the runners being grown now are considered jumbo runners (smaller than Virginia market types but large enough supplemental calcium is needed.)  Most growers will apply a 1x rate to both Virginia and runner market types but ½ to ¾ of a normal rate most likely will provide the needs for runner market types (see table 3-8 in 2018 Peanut Information for more discussion on rate response to gypsum.)  However, the 1x rate discussed in table 3-7 is our recommendation of all Virginia market types.