Manganese Effects on Yield and Nutrient Concentration in Leaves and Seed of Soybean Cultivars1

Abstract

AbstractCritical and sufficiency concentrations of Mn in soybean [Glycine max (L.) Merr.] leaves are levels which are deficient and adequate, respectively. These levels have been determined with a single cultivar. However, since several cultivars are often grown in Mn deficient areas, it becomes important to know if cultivars have different Mn requirements.A 3‐year study was conducted on an Olustee‐Leefield sand (Ultic Haplaquads — Arenic Plinthaquic Paleudults) near Tifton, Georgia to evaluate Mn treatments on soil test values, on nutrient concentration in leaves and seed, and on seed yields of eight soybean cultivars.The addition of Mn increased the amount of Mn extracted from the soil each year by the double acid (0.05 N HCl + 0.025 N H2SO4) and DTPA (diethylenetriaminepentaacetic acid) solutions, but double acid extracted considerably more Mn than did DTPA. Significant differences in yield, concentration of Mn in tissue, and seed weight among cultivars from Mn application were obtained only in the third year (1977) when the soil pH was increased to 7.0. The addition of Mn to the soil increased leaf Mn in all cultivars and seed Mn and seed yields in five of eight cultivars. Concentrations of Mn in recently matured leaves (R2 stage) varied among cultivars in untreated plots from 10 to 17 ppm and in Mn treated plots from 20 to 28 ppm. Seed Mn varied from 8 to 14 ppm in untreated plots and 13 to 20 ppm in Mn treated plots. Average seed yield (across cultivars) in the third year was increased 5.3 quintals/ha or 27% by Mn over no Mn with more than one‐third of the yield increase attributed to increased seed weight. Nutrients, other than Mn, in plant tissue were not affected by Mn treatments; however, small differences occurred among cultivars in concentration of P, K, Ca, Mg, Cu, Fe, and Zn in leaves and seeds.A regression equation indicated that the average critical and sufficiency levels of leaf Mn for eight soybean cultivars were 18 and 29 ppm, respectively. Our data suggest that several cultivars should be used to establish critical or sufficiency values for leaf Mn in order to develop an adequate range in values for the number of cultivars usually grown in Mn deficient areas.