Evaluation of soil sulphur fractions as sources of plant-available sulphur using radioactive sulphur

摘要

Abstract When an apparent steady state condition was reached during the incubation of three soils with 35S-labelled gypsum under growth chamber conditions, perennial ryegrass plants (Loliurn perenne L.) were grown and their S uptake was then related to levels of the various S fractions determined by six different methods. About 30-47% of the added S was taken up by plants. This uptake was related to decreases in extractable and HI-reducible S during cropping. The best correlation (r > 0.93) was obtained with S extracted with Ca(H2PO4)2-H2O and NaH2PC4-HOAc. The L values changed significantly with harvests in two of the soils studied. Mineralisation of indigenous soil S was greater in the presence of plants, but the amount of added S immobilised was unaffected by plants and extractants.