Two Soil Amendments Of Rich In Ca²⁺ On Translocation And Accumulation Of Cd In Rice Plants

In this study,uptake,accumulation,and transport of soil Cd in two typical rice cultivars were studied by applying calcium magnesium phosphate fertilizer?CMPF?and CaCl₂.Contents of available Ca,Mg,and Cd in paddy soil and Cd contents in brown rice were analyzed.Distribution and accumulation of Cd in various rice organs were discussed.Based on these studies,we tried to provide theoretical basis for reducing soil Cd in brown rice and for paddy soil improvement technology and application.The main research results are given as follows:?1?Application of CMPF could significantly enhance soil pH values,increase contents of TCLP extracted Ca and Mg in paddy soil,reduce contents of TCLP extracted Cd and exchangeable Cd in soil,and decrease bioavailability of soil Cd.?2?Application of CMPF could significantly increase of Ca/Mg contents and reduce Cd contents in different rice organs at different rice growth stages.There are significant negative correlations between Ca/Mg contents and reduce Cd contents in different rice organs,implying that there exists an obvious antagonism between Ca/Mg and Cd in rice plants.?3?In Soil A with Cd of 0.72 mg/kg,Cd contents in brown rice of Xiangwanxian 12 and Weiyou 46 are all lower than 0.2 mg/kg and meet the National Standard of Pollutants in Food?GB 2762-2012,Cd<0.2 mg/kg?.In Soil B with Cd of 5.38 mg/kg,Cd contents in brown rice of Xiangwanxian 12 are lower than 0.2 mg/kg.When applying amount of CMPF is higher than 0.4 mg/kg,Cd contents in brown rice of Weiyou 46 are also lower than 0.2mg/kg.?4?Applying CaCl₂ could significantly reduce soil pH values and enhance TCLP extracted Ca in soil and Ca contents in brown rice.With increasing CaCl₂ application,Cd contents in rice brown increase first and then decrease,and there is a significant negative correlation between Ca and Cd in brown rice.?5?Compared CMPF with CaCl₂,Cd contents in rice brown increase first and then decrease with increasing CaCl₂ application and Cd contents in rice brown decrease significantly with CMPF application.This is a probable combined action of the following three aspects:1)CMPF enhances soil pH values and inhibits Cd uptake in rice plants.2)There is a competition between Ca/Mg and Cd in paddy soil.Applying CMPF could increase TCLP extracted Ca/Mg and reduce TCLP extracted Cd in soil,resulting in decrease in Cd contents in brown rice.3)There exists an obvious antagonism between Ca/Mg and Cd in rice plants,and higher Ca/Mg contents in rice organs results in lower Cd contents.Applying CaCl₂ decreases soil pH and increases TCLP extracted Cd in soil,and Ca contents increases and Cd contents decreases in brown rice simutaneously.This implies that antagonism between Ca/Mg and Cd in rice plants is probable main role among these three aspects.