Abstract: In order to investigate the effects of Cr(Ⅵ) sewage irrigation on the soil microflora in different growth stages of rice,pot experiment was conducted using the japonica cultivar Wuxiangjing 14,and watered with simulated Cr(Ⅵ) wastewater at three concentrations: 0 mg·L^-1(CK),10 mg·L^-1(Cr10) and 50 mg·L^-1(Cr50).Results show that:(1) In different growth stages of rice,as compared with CK,the number of soil bacteria was significantly increased under Cr10 but significantly decreased under Cr50;while the number of soil fungi,actinomycetes and potassium solubilizing bacteria were significantly decreased with the increasing of Cr(Ⅵ) concentration.However,the number of soil phosphate solubilizing bacteria was significantly increased with the increasing of Cr(Ⅵ) concentration.(2) In different growth stages of rice,the sensitivity of soil microbes to Cr(Ⅵ) was different.It was higher in the early growth stage than in maturity stage for soil bacteria,and the reverse trends for soil fungi and actinomycetes were observed.(3) Adding SiO₂ into the pot soil significantly decreased the inhibiting activity of Cr(Ⅵ) to the number of soil bacteria from jointing to heading stage and to the number of soil actinomycetes in tillering and heading stages,but depressed the positive activity of Cr(Ⅵ) to the number of potassium solubilizing bacteria.

Key words: soil microflora, Cr(Ⅵ), paddy soil, growth stage, sewage irrigation