The influence of various nitrogen (N) and sulphur (S) forms on the uptake of manganese (Mn) in young spring barley (Hordeum vulgare L cv Golf) plants was examined in both a hydroponic system and in a soil-based system. The soil was a typical Danish Mn-deficient soil viz. a sandy loam soil developed on old marine sediments. Plants growing in solution culture with NO − 3 as the only N source had a higher Mn uptake than plants receiving mixtures of NO − 3 and NH + 4 . These findings were opposite to the results obtained in the soil-based experiments, where plants fertilized with NO − 3 as the only N source accumulated much less Mn than plants fertilized with NH + 4 . Combining the results of these experiments confirmed that NH + 4 acted as a powerful antagonist to Mn 2+ during uptake but that this antagonistic effect was more than compensated for by the influence of NH + 4 in reducing plant-unavailable Mn(IV) to plant-available Mn(II) in the soil. Furthermore the soil experiments showed that fertilizers containing sulphur in the form of reduced S (thiosulphate) had a strong mobilizing effect on Mn, and enabled the plants to accumulate large amounts of Mn in the biomass compared with oxidized S (sulphate). Thus, fertilization with thiosulphate may be very effective in alleviating Mn-deficiency in soils developed on old marine sediments where Mn availability is limiting plant growth.