Flue gas desulfurization residue: a boron source for alfalfa production

Abstract

Very little literature documents the fate of flue gas desulfurization (FGD) residues under field conditions when applied at agronomic rates. The objective of this study was to document the availability of FGD residue-borne boron (B) for alfalfa (Medicago sativa) uptake when applied to marginally B deficient soils. The FGD residue was applied at rates of 0, 0.46 and 3.74 Mg ha-1 (0.038 and 3.1 kg B ha -1 respectively) on a silt loam soil immediately prior to alfalfa seeding. Soil pH increased temporarily, but returned to background levels by the end of the first growing season. Alfalfa yields were unaffected by these rates of residue applications. Shoot B concentrations decreased as the growing season proceeded for the control treatment, but second and third cuttings of alfalfa produced on residue amended soil had increased B levels demonstrating that FGD residue was a readily available B source, particularly later in the growing season when native soil B availability decreased. Residue-borne B did not leach below 0.15 m.