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 fertilized at different N to S ratios were carried out under glasshouse conditions by using the "rhizobag" technique. The objective was to compare the induced-influence of rhizosphere and non-rhizosphere soil on N and S nutrition of the studied plants. Thus, SO42-S, NO3--N and NH4+-N concentrations, and 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 oilseed 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. Moreover, 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. This indicated a clearcut different influence between the two rhizospheres which oppositely induce the N and S nutrition of the two plant species.