Paddy Crop Rotation And Plant Mowing The Study Of Cd Accumulation In The Soil

This paper effects crop rotation of aquatic plants and rice that have large biomass,in order to recover farmlands from heavy metal pollution,reduce the cadmium in rice,thereby making them reaching national food safety standards.The crop pairs selected for the rotation are: early season rice-scirpus tabernaemontani,riris-late rice,pontederia cordata-late rice,artemisia selengensis-late rice,tobacco-late rice.Their recovery potential for cadmium pollution of the soil is studied,and reduction of the cadmium in soil is studied through separate planting of scirpus tabernaemontani and artemisia selengensis.These are purposed to study the crops' absorption of low,medium cadmium pollution of soil,and to reduce the rice's absorption of cadmium,thus improving the conditions;the recovery approach can easily be accepted by farmers,and provides technical references for recovery of farmland from heavy metal pollution at low,mediate level.(1)Based on preceding plant Cd accumulation ability analysis of the experimental results show that in chenzhou and zhuzhou soil through five kinds of crop rotation mode of planting,strongest for tobacco-late rice Cd accumulation ability;The second is Li Hao-late rice;Effect is poorer for iris-late rice,including tobacco highest accumulation of Cd in soil,tobacco on Cd content as high as 22.27 mg/kg.Li Hao Cd accumulation amount in soil after tobacco,Li Hao leaf Cd uptake of 13.53 mg/kg;The root of the Cd content is lower than that of leaf was 9.45 mg/kg.For crop plants to Cd contaminated soil remediation ability after the comparison of the experimental results can be concluded that the rice cadmium standards prescribed by the state is 0.2 mg/kg,but without the phytoremediation of soil,planting rice of Cd content as high as 0.82 mg/kg,after tobacco-late rice crop rotation of Cd content in rice is 0.42 mg/kg,is five kind of rotation in the pattern of Cd content in rice,followed by Li Hao-late rice crop rotation mode,the Cd content of rice is 0.53 mg/kg is also a blank Cd content in rice reduce more.The transport coefficients of Cd in plant leaves ranged from large to small is:the tobacco-late rice>Li Hao-late rice>Iris-late rice>Pontederia cordata L-late rice>early rice.(2)By comparing five rotation model of biomass,Preceding tobacco plant biomass was highest,followed by iris,barracuda grass,Li Hao and early rice biomass is low.Including tobacco biomass is 7.41 times Li Hao biomass,but after the crop plants before planting,did not have a great effect on late rice biomass,and the overall quality of dry matter was similar.In five kinds of crop rotation mode,the former crop plants on soil Cd extraction quantity highest tobacco and Li Hao;Each basin tobacco-late rice mode,the tobacco of Cd in soil extraction amount as high as 22.59 mg,followed by Li Hao-late rice mode,Li Hao for the extraction of Cd in soil total of 2.14 mg of Cd.In the rotation pattern of two soils,the plants from high over the total Cd extraction on order: the tobacco-late rice>Li Hao-late rice>Iris-late rice>Pontederia cordata L-late rice>early rice.The content of Cd in soil are reduced accordingly,reduce the content of Cd in soil tobacco-rice mode to 0.97mg/kg,the repair rate was 32.64%,effective state of repair efficiency is 32.88%,after the total content of soil-rice rotation after Li Artemisia Cd reduced 0.36mg/kg.Five kinds of the removal rate of Cd is one of the best tobacco rotation mode-late rice,followed by Li Hao-late rice.Early rice-scirpus tabernaemontani,iris-late rice and late rice barracuda grass-the low removal rate is three rotation mode.(3)The major conclusion of this paper is: As scirpus tabernaemontani and artemisia selengensis are planted separately and harvested,study results show: artemisia selengensis has cadmium absorption ability far higher than scirpus tabernaemontani;in the first harvest,the former has cadmium concentration coefficient of 10.76 and the latter 0.52;in the fourth harvest,the former has concentration coefficient of 16.60,25.93 times as high as the latter,which shows Artemisia selengensis has the great recovery potential.After the harvest,artemisia selengensis and scirpus tabernaemontani reduce the level of cadmium in soil by 29.86% and 23.61%.The cadmium concentration in soil grown with artemisia selengensis is 1.01 mg/kg,and the recovery efficiency is 29.86%,while the effective recovery efficiency of cadmium in soil is 28.77%.Furthermore,artemisia selengensis is local plants of Hunan Province,and can be easily accepted by the environment,and has strong purifying ability for soil pollution.From the study results it can be known that the soil grown with the crops for a period can be recovered and reach national standards,and that the crops can help soil recovery.