Effects of boron foliar fertilization on irrigated soybean (Glycine max L. Merr.) in the Mississippi River Valley Delta of themidsouth, USA

Abstract

Boron (B) deficiencies have been observed in some irrigated soybean fields in the lower Mississippi River Valley on silt loam soils of pH >7.0 and irrigated with water having high calcium (Ca) and magnesium (Mg). Boron fertilization effects on irrigated soybean grown using the Early Soybean Production System (ESPS) in the Midsouth have yet to be determined. Three commercial cultivars available for use in the ESPS were selected and foliar fertilized with a B solution at GS’s R3 and/or R5 at concentrations of 280 g B ha^-1, 560 g B ha^-1, or a split application at both R3 and R5 of 280 g B ha^-1. Established stands were greater in 2016 than 2015 (262,378 vs. 180,804 plants ha^-1) resulting in respective mean yields of 4239.7 vs. 3794.7 kg ha^-1, but no significant interactions with years were noted.  Yields of AG4632 were unaffected by B fertilization.  Boron fertilization of P47T36 at R5 generally improved yields (>4000.0 kg ha^-1) over the control (3668.6 kg ha^-1) and applications at R3 (<3900.0 kg ha^-1). The 560 g B ha^-1 treatment at R3 for P50T64 produced less seed (3742.5 kg ha^-1) than all other treatments while no other differences were noted. Some differences were noted in 100 seed weights but they were neither large nor consistent. It is doubtful that economic benefits to soybean in the Mississippi Delta would result unless a B deficiency was positively identified early in a growing season or in previous seasons.  It is concluded from this experiment, that foliar fertilization of soybean with B, as a general production practice, is not recommended.