| In recent twenty years,one important application of RE in China is in agriculture. Addition of RE with appropriate dose can raise crop production and improve crop quality,which has been conformed by many experiments. However,its mechanism has not been fully understood.With the increasing usage in recent years for agricultural and other purposes,the possible toxicological and ecotoxicological effects caused by these practices draw concerns of scientists from different disciples,so evaluating the safety of RE applied in agriculture becomes an important field in RE research.While considerable work has been done for the effects on crops Jess work was conducted for the effects on soil quality,especially soil environment in rhizosphere. The objectives of this study were,therefor to discribe the characteristics and effects of applying RE on soil mineral nutrition with a soil culture experiment as well as the effects of RE on translocation and uptake of mineral ions in rhizosphere with a simulating rhizosphere experiment. Our aim is to provide reference data for the mechanism of the effects of REE on crops and the safety evaluation of RE used in agriculture.1. In soil culture experiment,RE applications with appropriate dose in dry condition increased the contents of soil available N,whose no-effect value were 505mg/kg at eighth week,whereas higher levels of RE had negative effects,RE applications with both appropriate and higher dose in inundated condition reduced the contents of soil NH/-N and hydrolysable N. RE treatment concentrations showed significant positive correlation with the contents of soil exchangeable RE.and significant negative correlation with the contents of soil available P and soil pH value.There was no significant effects of RE on soil exchangeable cations,but applications of RE increased the contents of soil water soluble cations,especially that of Ca2* and Mg2+. It was also found that RE treatments in two weeks increased the contents of soil exchangeable Zn,reduced the contents of soil exchangeable Fe,increased the contents of soil exchangeable Mn in the dry condition andreduced them in the inundated condition,RE treatments in eight weeks enchanced the contents of soil exchangeable Fe,Mn and Zn.2. In rhizosphere culture experiment,RE applications with appropriate dose in three weeks significantly increased the biomass (dry matter) of rape and rice,and the effects of RE on the rape was better than the rice ,but they decreased or became little significant in eight weeks. Wether in three or 1 eight weeks,the biomass (dry matter) of rape and rice decreased significantly for higher RE treatments,and the inhibition of RE to the rice was stronger than to the rape.3. Wether at the third or eighth week,N,P,Kand Ca absorptions in rape and rice with RE treatments of appropriate dose increased ,the effects at the third week were better than at the eighth week,and the absorptions decreased significantly with higher RE treatments. Fe,Mn,Cu and Zn contents in the roots of rape and rice changed differently ,they all decreased in the roots of rape except Cu and increased in the roots of rice except Zn at the third week compared with control.4. RE applications enhanced REE absorptions in the roots of rape and rice. RE contents in roots had significant positive correlation with the contents of RE treatment concentrations and soil exchangeable RE concentrations,the correlation between RE contents in the roots and soil exchangeable RE concentrations was more marked,which indicated that soil exchangeable RE could be available composition absorbed by plants.5. Translocation and distribution pattern of Ions in the rhizosphere soil of crops were different remarkably with respect to different RE treatments and culture condition. Ions (mainly refering to Ca2',Mg2* and NCV et al.,which have higher concentration in soil solution) in rape rhizosphere with no RE and appropriate dose RE treatments moved mainly via a diffusion process up to a 3mm distance from the central compartment(C.C),and ma...
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