General agreement does not exist as to the most appropriate method to estimate plant available Mn in soils. In the current investigation soil and soil solution Mn were measured in limed and unlimed treatments of 11 acidic subsoil horizons and related to plant Mn concentrations, Mn uptake and growth of subterranean clover (Trifolium subterraneumL. cv. Mt. Barker) and switchgrass (Panicum virgatumcv. Cave‐in‐Rock). Manganese measurements were taken at planting and harvest and included: Mn extracted by 1MNH4OAc (pH 7), 0.01MCaCl2, 0.05MCaCl2, 0.033MH3PO4, 0.005MDTPA, 0.2% hydroquinone in 1MNH4OAc (pH 7), 0.01MNH2OH.HCl 4 2 in 0.01MHNO3, total soil solution Mn and concentrations and 2+ activities of Mn2+calculated from the GEOCHEM program. Measured and calculated values of soil solution Mn generally gave the best correlations with subterranean clover and switchgrass Mn concentrations and Mn uptake. Root Mn concentrations were highly correlated with soil solution Mn measurements taken at harvest with r=0.97 and r=0.95 (p<0.01) for subterranean clover and switchgrass respectively. The Mn extracted by 0.01M CaCl was also significantly correlated (p<0.01) with plant Mn concentrations and Mn uptake and proved to be better than the other extractants in estimating plant available Mn. Although Mn concentrations as high as 1769 mg/kg (shoots) and 8489 rag/kg (roots) were found in subterranean clover, Mn did not appear to be the major factor limiting growth. Measures of soil and soil solution Mn were not strongly correlated with yield. Both Al toxicities and Ca deficiencies seemed to be more important than Mn toxicities in limiting growth of subterranean clover and switchgrass in these horizons.