Timing of Foliar Manganese Application for Correction of Manganese Deficiency in Soybean1

Abstract

AbstractA consensus has not been reached on how often and at what growth stage to apply foliar Mn for alleviation of Mn deficiency in soybean [Glycine max(L.) Merr.]. Three field experiments were conducted to determine soybean response to a 1.12 kg Mn ha−1foliar application at the V6 (early), the R1 (late) and at both the V6 and R1 growth stages. Determinate ‘Essex’ soybeans were grown at two locations on Dragston fsl (Aeric Ochraquults) soils and ‘York’ on a Myatt fsl (Typic Ochraquults). The Ap horizon of the soils had pH levels from 6.3 to 6.8 and had low Mehlich 1‐extractable Mn levels from 0.8 to 1.6 mg kg−1. Foliar application of MnSO4increased soybean seed yields up to 2518 kg ha−1over the control. Yield increases were due to increases in seed weight and seed numbers. The average control Mn concentrations in the leaflets, trifoliolate leaves and seeds were 11.4, 9.3, and 8.5 mg kg−1, respectively. More Mn was translocated to the seed from the late than from the early foliar Mn treatment. Seed yields were higher from plants that received a single early spray than a single late spray. Soybean plants that received 1.12 kg Mn ha−1early and again late had higher yields than plants that received a single early spray. Full correction of soybean Mn deficiency by foliar Mn technique required multiple foliar Mn applications.