Fate of nitrogen and sulphur as affected by the rhizosphere of oilseed rape and barley

Within plants, sulphur (S), and nitrogen (N) equilibrium is a requisite for their normal development. Pot experiments with oilseed rape and barley fer tilized at different N to S ratios were carried out under glasshouse condit ions by using the "rhizobag" technique. The objective was to compare the in duced-influence of rhizosphere and non-rhizosphere soil on N and S nutritio n of the studied plants. Thus, SO42-S, NO3--N and NH4+-N concentrations, an d total N and S taken up by the plants were examined. Barley increased the pH of rhizosphere soil whereas no real change of pH was observed with oilse ed rape. Both plants took up all the NO3- present in the soil solution, but rapeseed took up greater quantities of NH4+-N and SO42--S than barley. Mor eover, the ratio values of N to S of the aerial parts of the rapeseed were significantly and positively correlated to those of soil available-N to -S ratios while this correlation was significant but negative with barley. Thi s indicated a clearcut different influence between the two rhizospheres whi ch oppositely induce the N and S nutrition of the two plant species.