Effect Of Soil Tillage And Irrigation Methods On Cd Accumulation And Distribution Of Rice In Cd Polluted Paddy Field

China is a large country of grain production,but in recent years,with the accelerated process of industrialization,the effect of heavy metal pollution especially cadmium pollution of rice is becoming more and more serious,how to deal with the cadmium pollution in paddy field,and realize the safe production of rice is the current research focus.The field and pot experiments were carried out in paddy field for double cropping rice with cadmium pollution in Xiangtan City,Hunan Province,to comparative study the effects of 5 kinds of double cropping rice soil tillage methods(double cropping rice under no tillage(DN),double cropping rice under plowing(DP),double cropping rice under rotary tillage(DR),rotary tillage in early rice and no tillage in late rice(RENL),plowing in early rice and no tillage in late rice(PENL))and different irrigation methods on soil available cadmium(Cd)content and accumulation and distribution of cadmium in rice.The main results are as follows:1.The highest yield of early and late rice was gained in DP in 2015-2016,and the second was PENL,the yield of DN and DR were lower.Plowing increased yield by increasing the number of effective panicles,and no tillage was beneficial to the increase of 1000 grain weight.2.The effect of soil tillage methods on soil available Cd content was extremely significant.The soil available Cd content of DN was higher,the next was DP,and PENL and RENL were beneficial to reduce the soil available Cd content.3.The content of Cd in roots was highest in DN,and the content of Cd in stems was increased by DR.It was easier to accumulate heavy metal Cd in rice panicle and grain by rotary tillage.PENL and RENL were beneficial to reduce the Cd content in the branch,empty grain,husk and rice;the accumulation of cadmium in the overground part of rice by plowing and rotary tillage treatments were increased year by year,while the increase in no tillage treatment was smaller;the amount of Cd accumulation in all parts of the plant showed the trend of stem > rice and leaf > empty grain and branch.4.Under the pot conditions,the highest total yield of two season was gained in DI treatment.The II and the intermittent irrigation of tillering-booting stage period(IITB)were advantageous to increase the number of effective panicles,and the IIFG could increase the grain number per panicle.5.In the field experiment conditions,the soil available Cd content in the whole growth period intermittent irrigation treatment(II)was higher than that in whole period shallow water irrigation treatment(SI)before full heading stage,after slightly lower than that in the shallow water irrigation treatment.Under the condition of pot experiment,the whole growth period deep-water irrigation treatment(DI)and intermittent irrigation from full heading to grain mid-filling period treatment(IIFG)were beneficial to reduce the soil available Cd content.6.Field experiments showed that the Cd content in stem,leaf,rice and rice bran in the II was higher than that in the SI at all growth stages.The results of pot experiments showed that the Cd content was higher in all parts of the panicle and grain of the II than that in other treatments.The Cd content in milled rice of the IIFG in the early rice season was the lowest,which was 0.0229mg/kg.The DI significantly decreased the Cd content in mature root,stem,leaf and grain,and the cadmium content of milled rice was 0.1527mg/kg,compared with S2~S7 were decreased by 77.98%,65.01%,72.64%,50.45%,46.36% and 73.61%,respectively.The Cd in rice plants was mainly accumulated in stems and leaves.The results of pot experiments showed that DI was beneficial to reduce the accumulation of Cd in the overground part of rice(especially the late rice),and the total amount of Cd accumulation in the overground part of rice was increased by II.The IIFG was beneficial to reduce Cd uptake and accumulation in rice.The difference in Cd accumulation in the overground part of rice was mainly deduced by effect of irrigation methods on the Cd content in the plants.In summary,the soil tillage of PENL and the irrigation method of IIFG were adopted in Cd polluted double cropping rice field could gain the higher rice yield,but also could reduce the soil available Cd content and cadmium content in roots and rice to a certain extent,so which were suitable to be applied in Cd polluted double cropping rice field.