Comparison of mineralization and distribution of soil sulfur fractions in the rhizosphere of oilseed rape and rice
2003
Hu, Z. | Haneklaus, S. | Wang, S. | Xu, C. | Cao, Z. | Schnug, E.
The effect of plant growth on the mineralization and distribution of soil sulfur (S) fractions (soluble SO4(2-), adsorbed SO4(2-), ester-bonded S, carbon-bonded S and residual S) in the rhizosphere of oilseed rape and rice was studied in a greenhouse experiment using a rhizobag technique. Significant differences of sulfur fractions between the rhizosphere and the non-rhizosphere were determined in dependence on crop type. The sulfur content of the microbial biomass was up to 72% higher in the rhizosphere than in the non-rhizosphere. The ester-bonded sulfur content was significantly lower in the rhizosphere of rice and oilseed rape. The results indicate that the arylsulfatase activity was higher in the rhizosphere than in the non-rhizosphere. The transformation of residual sulfur in the rhizosphere was related to crop type. Rice utilized residual sulfur more intensely, because of its aeration tissues from the top to the roots. Compared to the non-vegetated control soil, the residual sulfur fraction was 20 to 78% lower in the rhizosphere of the treatments where rice and oilseed rape were grown. Ratios of inorganic SO4(2-)-S in the rhizosphere to the non-rhizosphere varied between 1.3 and 3.1, indicating an enrichment of SO4(2-)-S in the rhizosphere. Growing oilseed rape, the ester-bonded and carbon-bonded sulfur increased by 47% and 25% in the rhizosphere compared to the control. In contrast, the two fractions decreased by 75% and 30% in the rhizosphere of rice. These findings show that the mineralization of organic sulfur was related to crop type and that all fractions of organic S are on principle bio-available.
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