Explanation For The Difference In The Effects Of Planting Different Crops On Degradation Of Diuron In Soil

To explore phytoremediation potentiality of soils polluted by herbicide, ryegrass (Lolium multiflorum Lam.) , lxeris (Lxeris sonchifolia Hance) and mungbean (Vigna radiata Wilczek) were used for investigating the effects of plantation of these crops on the degradation of diuron by pot experiment method and incubation experiment method. The main results were as followed:1. After cultivation of these plants in soils contained 1-2 mg/kg diuron for 30-60 days, the residue of diuron reduced by 30.56%-72.21%. Moreover, the effect of planting mungbean on degradation of diuron was more significantly than that in ryegrass, while the effect in lxeris was not significantly as in ryegrass and mungbean.2. After planting for 30-60 days, the amount of both microorganism and microbial biomass C were higher than that in control soil notably (P<0.05 ) . The population of microorganisms was the most in mungbean planting soil, next in ryegrass planting soil, and the least in lxeris planting soil.3. After the addition of l-2mg/kg diuron to the soils for 15 days, the residues of diuron in rhizosphere soil were all less than that in bulk soil notably (P<0.05) , Furthermore, as time was delayed, the residue of diuron in rhizosphere soil was reducing constantly. However, the population of microorganism had an increasing trend. The residue of diuron in mungbean rhizosphere soil was the least, next was ryegrass, and the most was lxeris. Furthermore, the diuron residue increased sharply after sterilization. During the degradation process, there was a notably negative relationship between the logarithm of the microorganisms population and the residues of diuron in soil (P<0.01) .4. After the addition of root exudates to the soils contained 1 mg/kg diuron for fifteen days, the residue of diuron in soil was notably lower than that in the control. The effect of root exudates on degradation of diuron in soil was impacted by the components of the exudates. In the root exudates of mungbean, the contents of water-soluble nitrogen and carbohydrate were higher and C/N was lower. After adding the root exudates of mungbean into soil contained diuron, the microorganisms population increased in a large amount, which resulted in notably lower residue of diuron than that in soils contained lxeris and ryegrass root exudates . On the contrary, there were few carbohydrate and water-soluble nitrogen in lxeris root exudates, so its effect on microorganism activity and diuron degradation was insignificant.5. The photochemistry degradation of diuron in oxalic acid-Fe system could be observed in natural light condition, while the degradation of diuron could not detected without irradiation.