Effect of Calcium Source and Irrigation on Soil and Plant Cation Concentrations in Peanut (Arachis hypogaea L.)

Calcium improves seed formation and development of peanut kernels. Two primary sources of Ca fertilization in peanut are gypsum (CaSO4) and dolomitic lime (CaMg[CO3]2+CaCO3). Objectives of this research are to determine whether gypsum, lime, or application of both influences pH, extractable [Ca], [Mg], and [K] in the soil along with nutrient absorption, yield, and total sound mature kernels (TSMK) in peanut pods in irrigated compared to non-irrigated conditions. Experiments conducted in Tifton, GA in 2016 and 2017 evaluated Ca treatments with no supplemental Ca fertilizer, gypsum (330 kg Ca/ha) applied at first bloom, lime (897 kg Ca/ha) applied at planting, and lime (897 kg Ca/ha) applied at planting followed by gypsum (330 kg Ca/ha) applied at first bloom. Irrigating increased soil pH, [Ca] and [Mg] in pods, plus yield and TSMK of peanut. Irrigation also decreased [K] in pods, which was correlated with increased pod [Ca]. Soil pH and soil [Ca], [Mg], and [K] were influenced by fertilizer treatment, along with [Ca] and [Mg] in pods. Applications of lime increased pH and soil [Ca]. Lime also increased soil [Mg] when applied alone, but not when gypsum was also included. Application of gypsum reduced soil [Mg] when applied alone, but not when lime was included. The inclusion of both lime and gypsum reduced soil [K] compared to no application. These results display the competition of cations in soil. In peanut pods, using lime and gypsum increased [Ca] compared to no application, or only lime. However, when only gypsum was used, it reduced [Mg] in pods compared to a lime application or no fertilization. Although Ca fertilization did not affect yield, TSMK was greater when lime followed by gypsum were applied in sequence than where neither were applied in 2016. It is important to realize that applications of Ca can also influence concentrations of other cations important for growth. Peanut growers are encouraged to conduct soil tests to ensure soil [Mg] is not deficient or borderline before choosing to apply gypsum, and may require a supplemental Mg fertilizer if dolomitic lime was not applied.