Crop influence on mobile sulphur content and arylsulphatase activity in the plant rhizosphere

Abstract

The changes of mobile sulphur (S) contents were investigated in the plant rhizosphere using precise model experiments with rhizoboxes. The tested plants were winter wheat (Triticum aestivum L.), winter rape (Brassica napus L.) and white lupine (Lupinus albus L.). In this experiment, a Cambisol from a precise field experiment treated with sewage sludge or manure was used. Total extractable S concentration and mineral S (S-SO42-) concentration in the water extract were higher in the plant rhizosphere (< 6 mm from the root) compared to the so-called bulk soil (> 6 mm). The contents of total extractable S0 decreased in order: lupine (5-35 mg/kg) > rape (4-18 mg/kg) > wheat (1.5-3 mg/kg). The same order was observed for mineral S-SO42- where the contents in soil extracts were 1-10 mg/kg, 2-7 mg/kg, and 0.5-3 mg/kg, respectively. The highest total extractable S and mineral S (S-SO42-) contents were found in the treatments fertilized with organic fertilizers. In the case of rape and wheat the arylsulphatase (ARS) activity was higher in the rhizosphere compared to the bulk soil; the opposite was recorded for lupine. It was acknowledged that the ARS activity was higher in the treatments fertilized with organic fertilizers (manure or sewage sludge) with all three tested plants. The highest determined ARS activity was found after wheat cultivation, the lowest after the lupine cultivation. The organic sulphur content followed an opposite tendency (lupine > rape > wheat).