Effects Of Different Water Management On Heavy Metal Content In Rice

In order to explore the effect of different water management on the content of heavy metals in rice plants,two experiments were conducted:1.to study the effects of different water management on the content of heavy metals in the rice,with V1 Zhunliangyou 608,V2 Wuyou 308,V3 Yliangyou 488)as three different varieties of rice,the potting experiment was carried out in the Rice Science Research Institute of Hunan Agricultural University in 2016.Three different water management models were designed.(1)CFI(continuous flooding irrigation)was maintained at the time of rice growth,while the soil was kept in 2-3cm water layer flooded state.(2).CMI(controlled moisture irrigation)was maintained at the time of rice growth,while the soil surface was kept in wet(soil table no water but soil water content of 100%);(3).PWI(periodic wet irrigation)began the transplanting,the first irrigation 2-3cm water,until it consumed to no water,the soil has just cracked irrigation next time the water,so the cycle;2.to study the effects of different water management on cadmium content and morphology of the rice rhizosphere soil,using V1: Yuzhenxiang and V2: Xiangwanxian 12 as two different varieties of rice,the pot experiments were carried out at the Rice Science Research Institute of Hunan Agricultural University in the first half of 2017.Three different water management models(CFI,CMI,PWI)were designed.The water treatment method was the same as the test one.The main results were as follows:1.Continuous flooding irrigation could significantly reduce the cadmium content of rice.At the maturity time,the content of Cd was the lowest,which was 0.12 mg/kg under the condition of CFI;the content of Cd was the highest,which was 2.78 mg/kg under the condition of CMI.But continuous flooding irrigation could increased the arsenic content of rice;controlled moisture irrigation could reduce the Cr content of the stem Significantly;controlled moisture irrigation could reduce the As content of grain,the content was 0.22 mg/kg.The content of chromium and lead in paddy rice was not significantly different under different water management conditions,and the water management had no significant difference in the absorption of chromium and lead in paddy rice.The effect of rice stem on the enrichment of cadmium was the strongest,which was 30.73.From the stem to the grain,the transport coefficient of cadmium was the highest under the water management of the periodic wet irrigation,The highest was 0.3,from stem to leaf,the transport coefficient of cadmium was the biggest under the water management of the periodic wet irrigation,The highest was 0.68.2.The Heavy metal accumulation in rice between different varieties of rice plants was different.Under the condition of the same background value of soil Cd content,zhunliangyou 608 had the strongest ability of absorbing cadmium,it reach to 40.75.whether its stem,leaf an grain,the Cd content was higher than the other two varieties.The differences between Arsenic and cadmium accumulation in rice plant was negatively correlated among the three different water management.Compared with Flooding irrigation conditions and phased irrigation condition3.Under the condition of the flooded,the content of arsenic was increased and cadmium content of cadmium was relatively reduced.Under the dry-wet alternate condition,the two was opposite,arsenic content was lower,however,the content of cadmium was relatively higher.4.The soil environment was one of the most important restrict factors that accumulation of heavy metals in rice plant,the influence of different water management on soil environment was obvious,and the soil pH on the activity of heavy metals in soil played a very important role.In the early stage of rice growth,under the mode of flooding and wet irrigation,pH was acidic,pH was increased.In the late stage of rice growth,under the mode of wet irrigation,soil pH was a little alkaline and dry-wet alternate was neutral.5.Although it was a certain amount of heavy metal cadmium in soil,its existence forms will change with the environment in a state of relative balance,but the highest content of cadmium in wet irrigation in the possession of the proportion was also the biggest,the content were 0.08 mg/kg and 0.11 mg/kg in the two varieties Yuzhenxiang and Xiangwanxian 12.But the forms of carbonate combination state and the iron and manganese oxidation state cadmium were not particularly stable,it was easy to ionization state become exchangeable cadmium,while the three active of cadmium on the total amount was the highest in flooded conditions,dry-wet alternate minimum,the content were 0.06 mg/kg,0.05 mg/kg and 0.07 mg/kg.Generally speaking Water management had a significant effect on cadmium and arsenic in rice,but had no significant effect on chromium and lead.Long-term flooding could effectively reduce the content of cadmium in rice.The soil pH was increased by wet irrigation,but the difference in soil pH was not significant under the condition of long-term flooding irrigation and dry wet alternate irrigation.From the point of view of heavy metal pollution to the whole country,we should consider the long-term flooding irrigation to effectively inhibit cadmium content in rice and protect human health.