Calcium Uptake in Irrigated and Non-Irrigated Runner Peanut.

Calcium (Ca²⁺) is important in peanut (Arachis hypogaea L.) production as it improves quality and yield. The two main sources of Ca²⁺ fertilization in peanut are flue gas desulfurized (FGD) gypsum (CaSO₄) and dolomitic lime (CaCO₃). This study was conducted to determine whether gypsum, lime, or a combination of both increase Ca²⁺ uptake, yield, and grade (% Total Sound Mature Kernels [TSMK]) with or without irrigation. Peanut was grown in 2016 on a Tifton loamy sand in Tifton, GA. Irrigated and non-irrigated blocks (main-plot effect) with four treatments of Ca²⁺ sources in each block (sub-plot effect) were applied in a split plot design with eight replications. The treatments in each irrigated and non-irrigated block included: 1. gypsum (330 kg Ca²⁺ ha^-1) plus lime (897 kg Ca²⁺ ha^-1) at planting, 2. gypsum (330 kg Ca²⁺ ha^-1) at first bloom (approximately 35 days after planting), 3. lime (897 kg Ca²⁺ ha^-1) at the time of planting, and 4. a non-treated check that received no supplemental Ca²⁺. Typical soil test Ca²⁺ was initially in the range of 569- 1151 kg Ca²⁺ ha^-1 in the pegging zone (top 8 cm of soil) at planting. Non-irrigated treatments (0.85% K⁺) had higher K⁺ concentration in the pod than irrigated treatments (0.65% K⁺). Gypsum plus lime (0.089% Ca²⁺), gypsum (0.08% Ca²⁺), and lime (0.081% Ca²⁺) treatments had greater concentration of Ca²⁺ in the pods than the treatment that received no Ca²⁺ (0.07% Ca²⁺). Based on the 2016 study, irrigation was significant for yield (p<0.0001). Irrigated peanut (6761 kg ha^-1) yielded more than non-irrigated peanut (5051 kg ha^-1) averaged over Ca²⁺ treatments. There was no significance between Ca²⁺ treatments (p>0.10) and no interaction between irrigation and Ca²⁺ treatment effects (p>0.10) for yield. Peanut grade based on percent total sound mature kernel (TSMK) was significantly greater in gypsum plus lime treatments (76.4%) and gypsum (76.2%) treatments than lime (75.1%) or non-treated peanut (74.6%). Irrigation plays a role in moving Ca²⁺ into the peanut plant, specifically the pods. With the use of irrigation and Ca²⁺ sources in the form of dolomitic lime and FGD gypsum, pod Ca²⁺ levels, yield and TSMK will increase when soil Ca²⁺ levels originate above 560 kg Ca²⁺ ha^-1.