Boron fertilization influences on soybean yield and leaf and seed boron concentrations

Soybean [Glycine mar (Merr.) L.] is considered relatively insensitive to B deficiency. However, B deficiency has recently become a common nutrient deficiency of soybean in northeast Arkansas. Field studies were conducted on four alkaline silt-loam soils in northeast Arkansas to determine the influence of B application time and rate on soybean growth, tissue B concentration, and seed yield. Boron fertilizer was applied at 0, 0.28,0.56,1.12, and 2.24 kg B ha(-1) near the V2 or R2 growth stages. Boron fertilization had no significant effect on soybean yield at one site but increased seed yields from 4 to 130% at three sites. At the most responsive site, B application at V2 increased yields by 13% compared with applications at R2. In contrast, at a site where leaf B concentrations were sufficient for soybean receiving no B, B applied at the R2 stage significantly increased seed yields by 5% compared with V2 B applications. Trifoliate leaf B concentrations at the R2 stage increased as B rate increased. Seed B concentrations also increased as B rate increased. Boron applied at the R2 stage resulted in equal or greater seed B concentrations than B applied at the V2 stage. Application of 0.28 to 1.12 kg B ha(-1) during early vegetative or reproductive growth was sufficient to produce near maximal yields. The expected severity of B deficiency plus fertilizer and application costs associated with B fertilization should be considered when selecting the most appropriate B fertilization strategy.