Effects Of Elevated Atmospheric Ozone Concentration On The Transformation Of Zn Forms In Soil Subject To Rice-Wheat Rotation

Due to the increase of ozone concentration in troposphere,it has already brought some negative impacts on the normal growth and the safety in production of crops.However,at present,there is little research on how forms of zinc would be changed in rice-wheat rotation agro-ecosystem when atmospheric ozone concentration increases.This research was aimed to study the form transformation of zinc in different soil and the growth of plant during complete growth period of wheat and rice under the condition of increase of ozone concentration in troposphere.Therefore,OTC-1 open top chambers were used to start potted experiment to explore the form transformation of zinc in soil,growth of plants and the concentration of zinc in crops.The main results are as follows:?1?The increase of ozone concentration had a negative effect on the health of plants growing and on the biomass.During the wheat season,when the content of exogenous zinc reached to 400mg/kg,the biomass of grain decreased significantly,which was decreased by 4.13%;during the rice season,the biomass of grain significantly dropped by 2.92%in soil without pollution.The biomass of roots significantly dropped by 7.72%?200 mg/kg Zn?and 4.46%?400 mg/kg Zn?when exogenous zinc was added to the soil during the paddy season.?2?The increase of ozone concentration showed a tendency that the zinc content in wheat grain would be decreased in non-polluted and low-polluted?200 mg/kg Zn?soil,which significantly decreased by 11.35%in low-polluted soil.When the content of exogenous zinc reached to 400 mg/kg,the zinc content in wheat grain showed an increasing tendency and it has significantly increased by 17.86%in the part of straw.In the experiment of rice,the increase of ozone concentration has reduced the zinc content of visceral organs in non-polluted and low-polluted soil.The zinc content of straw and grain significantly decreased by 32.86%?26.42%.In high concentration polluted soil,the zinc content of root and straw increased by 2.27%and 29.09%.?3?The increase of ozone concentration led to the tendency of Zn concentration increasing in the topsoil during the wheat season and the difference was not significant.However,there were different effects on the available Zn concentration appearing in different soil layers treated with different soils at different growth stages.Significant differences caused by the increase of ozone concentration mainly occurred in the late growth period,and the main phenomena were increasing the available Zn concentration in the surface layer?0?5 cm?and the deep?10?15 cm?soil layer and reducing the effective Zn concentration in the middle layer?5?10 cm?.Significant differences in an earlier period were in advance when exogenous zinc was added to the soil,for example,the concentration of available Zn in low-polluted soil was significantly different at tillering stage.The concentration of available Zn in contaminated soils was still increasing under the ozone fumigation,but decreasing during the deep soil jointing stage and heading stage.?4?The increase of ozone concentration had the tendency to decrease the available Zn concentration in the topsoil during rice season,the difference was not significant.The significant Zn concentrations in different soil layers were not alike at different growth periods.The significant differences were mainly in the middle and early growth period,including tillering and jointing periods.In the non-polluted soil treatment,the increase of atmospheric ozone concentration reduced the available Zn content in the surface soil.Ozone fumigation increased the amount of available Zn in the surface soil when 200 mg/kg of exogenous zinc was added.The ozone fumigation made the soil available Zn concentration in the deep soil increased significantly when the pollution was more serious.?5?The elevated O₃ concentration had no significant influence on the bioavailability of soil Zn in the whole topsoil?0?15 cm?and had the tendency to increase the WAS?Weak Acid Soluble fraction?and the DTPA Zn concentration in the topsoil during the wheat season.The decreased tendency of concentration appeared when 200 mg/kg of exogenous zinc was added.The effect of DTPA extracted Zn concentration on the non-polluted soil treatment in different soil layers during the rice season was decreased,and the effect on soil contaminated soil was improved.