Uptake and timing of calcium in runner peanut (Arachis hypogaea L.)

Peanut production in the southeastern United States is often limited due to low Ca availability. Gypsum and lime are common Ca supplements for peanut, but the indeterminate nature of peanut and variable solubility of these products adds uncertainty to timing of Ca amendments. Two sets of field trials were performed in southern Alabama from 2012 to 2014 under both irrigated and non-irrigated conditions using two runner-type peanut cultivars (Georgia-06G and Georgia Greener) to determine Ca uptake patterns and timing of amendments. Calcium uptake was evaluated by pod development stage with four soil Ca treatments: 560 and 1120 kg ha-1 gypsum applied at early bloom, 1120 kg ha-1 lime at planting, and an untreated control. Developmental stages were determined by the hull scrape method. The timing of gypsum and lime was evaluated using metrics of peanut yield, grade, germination, and seed Ca. Treatments included a single application of gypsum at planting and early bloom, split applications of gypsum at planting/early bloom and early/mid-bloom, lime at planting, lime at planting plus gypsum at early bloom, and an untreated control. Results suggested that peanut absorbed Ca throughout the entire growing season and that seed Ca concentration could be used as an indicator of earlyseason seed quality. Split applications of gypsum at early/mid-bloom tended to have a superior performance than a single application at planting or early bloom and split applications at planting/early bloom. Supplemental gypsum at early bloom combined with lime at planting further increased Ca availability under non-irrigated conditions relative to the lime-only treatment. This study provided helpful information for Ca nutrient management for peanut.