Influence of Application Variables on Efficacy of Manganese-Containing Fertilizers Applied to Peanut (Arachis hypogaea L.)

Abstract

Abstract Several formulations of the essential element manganese (Mn) are commercially available for application to peanut (Arachis hypogaea L.). Research was conducted in North Carolina to compare accumulation of Mn in peanut leaves, stems, and pods following application of water soluble manganese sulfate including 17.5% Mn (Techmangum® or Man-Gro DF®) and liquid Mn formulations including 5.0% Mn (Manganese Xtra©) or 8% Mn (Nutrisol 8% Manganese™). Experiments were also conducted to determine the influence of herbicides, adjuvants, and selected fungicide and insecticide combinations on Mn accumulation in peanut leaves. A second experiment was conducted to determine if efficacy of clethodim, imazapic, imazethapyr, lactofen, sethoxydim, and 2,4-DB was affected by Mn formulations when applied in mixture. Experiments were also conducted to determine the effect of Mn on efficacy of the fungicides azoxystrobin, chlorothalonil, pyraclostrobin, and tebuconazole. More Mn was found in leaves when dry formulations of Mn were applied compared to liquid formulations, reflecting the higher amount of actual Mn delivered per ha based on manufacturer recommendations of these products. Accumulation of Mn was higher when Mn was applied with the herbicides clethodim, imazapic, and lactofen compared with Mn alone or Mn plus 2,4-DB. Accumulation of Mn was similar for Mn alone or most combinations of Mn with fungicides and insecticides. Manganese did not affect corn (Zea mays L.) control by clethodim or sethoxydim; large crabgrass [Digitaria sanguinalis (L.) Scop.] control by clethodim; Palmer amaranth [Amaranthus palmeri (S.) Wats.] control by imazethapyr; sicklepod [Senna obtusifolia (L.) Irwin and Barneby] control by imazapic, imazethapyr, or 2,4-DB; or tall morningglory [Ipomoea purpurea (L.) Roth] control by imazapic. In contrast, common ragweed (Ambrosia artemisiifolia L.) control by lactofen was reduced by dry manganese but not the 8% liquid solution. Peanut canopy defoliation was similar when the fungicides azoxystrobin, chlorothalonil, pyraclostrobin, or tebuconazole individually were compared alone, with Mn, or Mn plus the insecticide lambda cyhalothrin.