Effect of Ca Source on Runner Peanut Yield, Grade, Seed Ca, and Germination.

Peanuts require sufficient Ca in the pegging zone for proper development.  Sandy soils in the southeastern Coastal Plain, which is the major peanut producing area in the United States, are known for their inability to retain cations (e.g., Ca); therefore, addition of Ca supplements is a common practice to increase soil Ca.  Many Ca supplements are available to peanut producers; however, the efficacy of these products is not well understood.  The objective of this study was to evaluate the effectiveness of various Ca sources on peanut yield, grade, seed Ca, and germination.  This study was conducted under non-irrigated conditions in 2012 and under both non-irrigated and irrigated conditions in 2013 at Wiregrass Research and Extension Center (WREC) in Headland, AL; and under non-irrigated conditions in 2013 at Gulf Coast Research and Extension Center (GCREC) in Fairhope, AL.  Three commercial types of gypsum, two types of lime, and one liquid Ca fertilizer (Hi-Cal) were evaluated using two currently popular peanut cultivars in the Southeast, Georgia-06G and Georgia Greener.  Gypsum types included AgriCal, which is a flue gas desulfurized (FGD) gypsum, USG 500, which is a naturally mined gypsum, and PCS Wetbulk, which is a phosphogypsum.  Lime types included a calcitic lime and a dolomitic lime.  Gypsum was applied at early bloom at 560 kg ha^-1 in 2012 and 1120 kg ha^-1 in 2013.  Lime was applied at 1120 kg ha^-1 at planting.  Hi-Cal was applied at early bloom at 375 L ha^-1 using a field sprayer.  Overall analysis found that effectiveness of the three types of gypsum did not significantly differ when applied at the same rate, but USG 500 tended to perform better than AgriCal and USG 500.  Lime was found as effective as gypsum on improving peanut yield, grade, seed Ca, and germination.  Greatest seed Ca occurred at 3 of the 4 site-years following application of lime at planting.  Under irrigated conditions in 2013, Hi-Cal did not significantly improve peanut yield, grade, seed Ca or germination compared to the untreated control treatment.  Overall, results indicate that peanut producers can use either lime or gypsum as source of supplemental Ca, whereas Hi-Cal is not recommended due to its low efficacy.  Either types of gypsum evaluated in this study may be used, but USG 500 is preferred.