The Effect Of Applying Organic Fertilizer On Arsenic Accumulation In Double Cropping Rice

Bulletin of the national survey of soil pollution shows that arsenic（As）exceed the standards of 2.7%,the soil As pollution seriously affects the sustainable development of agriculture.Rice is more prone to accumulate As than other crops,reducing the transfer of As from soil to rice and ensuring the safe production of rice is an urgent problem to be solved.The in-situ passivation remediation technology of heavy metals in soil is widely used,due to its short cycle and the ability of achieve remediation and production simultaneously.In this study,a paddy soil from Jiangxia District,Wuhan City was selected to investigate the effects of organic fertilizer application on soil As speciation,and the absorption of As in early and late rice.By indoor soil incubation experiment,the effects of organic fertilizer combined with iron containing materials（Fe Cl₃ and Fe₂O₃）on the speciations of soil As were analyzed,in order to seek for effective measures and methods to reduce the bioavailability of As in paddy soils.The main research results are as follows.（1）Explored the effect of organic fertilizers application on the As speciation in early and late rice soils.The application of organic fertilizer reduced the active As（exchange and specific adsorption）content in bulk soil of rice by 7.2%to 18.7%,but the labile As in rhizosphere soil increased by 13.5%-13.8%,indicating that the application of organic fertilizers promoted the transformation of labile to stable As fractions in bulk soil,while decreased the stable As contents in rhizosphere soil.（2）Analyzed the effect of organic fertilizers application on the absorption of As by rice.In early rice,the application of organic fertilizer significantly increased the As accumulation by 14%on iron film of root surface,reduced the As content in rice stem by31.1%,and increased the As content in grains by 153.7%.As foe late rice,the As contents in the roots and stem were significantly increased by 80.2%and 57.4%,respectively,whiell it was significantly decreased by 28.2%in the grain.The correlation analysis results showed that the As content of iron film on the root surface was negatively correlated with the contents in roots,stems and rice husks,while the grain As content was significantly negatively correlated with the As in stem（r=-0.63,P<0.05）.It can be seen that the application of organic fertilizers promoted the accumulation of As in iron film on the root surface of early rice,leading to the migration of As from stems to grains.But it promoted the accumulation of As in the roots and stems of late rice,and inhibited the accumulation of As in the grains.（3）The effects of organic fertilizers and iron-containing materials on soil As speciations were studied.For single application of organic fertilizer,soil specific adsorbed As was increased by 11.4%,while amorphous iron aluminum oxide bound As and residual As were decreased by 3.0%-3.2%.Organic fertilizer combined with Fe Cl₃ resulted in a12.2%decrease in soil specific adsorbed As content and a 7.5%increase in residual As content.It can be seen that single application of organic fertilizer treatment promoted the transformation of stable to labile As fractions in soil,while organic fertilizer combined with Fe Cl₃ treatment facilitated the transformation of labile to stable As in soil.Therefore,organic fertilizer combined with Fe Cl₃ can be considered to reduce the activity of soil As in the future.