Fertilizer sulphur uptake and transformations in soil as affected by plant species and soil type

The fate of fertilizer sulphur (S) in soil is important to S availability to plants and consequently, the crop growth and quality of the harvested products. In a pot experiment, we studied the partitioning of S-35-labelled Na2SO4 in soil compartments (S-35 in CaCl2 extract, labile and non-labile S-35 determined by hot water extraction) and in plant biomass. Rape (Brassica napus) and barley (Hordeum vulgare) were chosen for their contrasting S requirements. They were cultivated 28, 42 and 63 days in two contrasting soils: a calcareous soil (Rendzic Leptosol, pH 8.2, 2.3% organic C) and an acid brown soil (Fluvic Cambisol, pH 5.3, 1.0% organic C). Microbial activity was stimulated by the addition of glucose alone or glucose with N and P. Rape took up 2-3 times more S than barley. For both species, S accumulation in shoots was an exponential function of shoot biomass: S in shoots=alpha(shoot biomass)(1-beta), which suggests that the content of S in the shoot might be used as an index of plant S nutrition. In the calcareous soil, CaCl2-S-35 dominated whereas in the acid brown soil, labile S-35 extracted by hot water (HW-S-35) and CaCl2-S-35 were equally important. In both soils, CaCl2-S-35 was decreased by plant cultivation and when C was added whilst S-35 in non-labile forms increased in parallel. In case of rape, the effect of the plant on S-35 transformations in soil was of the same order of magnitude as the effect of the soil type. (C) 2007 Elsevier B.V. All rights reserved.