Variation of rhizosphere environmental factors of sugarbeet seedlings under Na2CO3 stress and their correlation.

Abstract

To study the effect of saline-alkali stress on dry mass, rhizosphere soil enzyme activities and soil microbial quantities, pot experiments were designed two sugar beet varieties, 'KWS0143' (strong tolerance to saline-alkali) and 'Beta464' (weak tolerance to saline-alkali) planted in different Na2CO3 concentrations [0% (control), 0.4%, 0.8% and 1.2% of soil], and the dry mass of seedlings,soil enzyme activities and amount of microbiology in soil were recorded. The results showed that compared with the control, the dry mass of seedlings was significantly increased in the treatment of 0.4% Na2CO3, while it was significantly decreased in the 0.8% and 1.2% Na2CO3 treatments. Significant differences among treatments were observed. The soil urease, alkali phosphatase and peroxidase activities in the root rhizosphere of seedlings presented a similar tendency under different concentrations of Na2CO3. Compared with the control, the enzyme activities with the treatment 0.4% Na2CO3 were not significantly enhanced, while those in the treatment of 0.8% and 1.2% Na2CO3 were significantly reduced. All the soil enzymes' activities in 'KWS0143 were higher than in 'Beta464'. The 0.4% Na2CO3 did not lead to significant change of soil microbial community, but 0.8% and 1.2% Na2CO3 sharply decreased the amount of soil bacteria, fungi and actinomycets (P<0.05). The amount of rhizosphere soil microbe in 'KWS0143' was higher than in 'Beta464'. There were significantly positive correlation among the dry mass, soil enzymes and soil microbe of the two varietie. Path coefficient analysis showed the determinant coefficient of 'KWS0143' dry mass was in order of sctinomycetes > bacteria > peroxidase > urease > fungi > alkali phosphatase, while that 'Beta464' dry mass was in order of actinomycetes > peroxidase > urease > fungi > alkali phosphatase > bacteria.