紫云英翻压条件下生物炭施用量对水稻Cd迁移积累的影响

Effect of Biochar Application Rate on Cd Accumulation and Transportation in Rice under the Condition of Rolling Astragalus sinicus into the Soil

【目的】稻田重金属污染已成为威胁我国粮食安全的主要问题之一。紫云英是我国南方种植水稻的主要绿肥作物,为研究翻压紫云英条件下,化肥配施生物炭对水稻产量及水稻镉(Cd)吸收、迁移和积累的影响。【方法】采用盆栽试验,在紫云英替代30%氮肥条件下,设置4个生物炭添加水平[CK(0 g/kg),C25(2.5 g/kg),C50(5 g/kg),C100(10 g/kg)],分析不同生物炭施用量对水稻生长及镉迁移积累的影响。【结果】生物炭表面具有多个不规则球状凸起,球状凸起表面有少量残屑附着且生物炭自身含有羟基、羰基和羧基等较多的含氧官能团;生物炭的施加可明显提高水稻各器官干物质量,C50处理水稻根干物质量显著(P<0.05)高于C25和C100处理,分别提高了30.9%和44.4%;其水稻秸秆和籽粒干物质量显著(P<0.05)高于CK和C100两个处理,秸秆干质量分别提高了14.3%和14.1%,籽粒干质量分别提高了52.5%和26.3%;与不添加生物炭相比,施用生物炭能明显提高水稻籽粒产量,在25 g/kg和50 g/kg的生物炭添加量时显著提高,分别提高了52.5%和33.7%;生物炭的施加可降低水稻籽粒中的Cd含量,C25、C50、C1003个处理较对照分别降低了13.2%、14.1%和11.0%;生物炭能抑制Cd在水稻各器官中的转运,所有转运过程的转运系数(TF)均有降低,与对照相比,TF;的降低幅度为5%~11.6%,TF;的降低幅度为1.5%~10.4%,TF;的降低幅度为6.1%~12.1%。【结论】生物炭具有较大的比表面积和多种含氧官能团,能有效钝化土壤重金属;翻压紫云英条件下添加生物炭不仅能提高水稻产量,还能降低水稻籽粒中的Cd含量,抑制Cd向水稻籽粒的转运,该施肥方案对Cd污染土壤的水稻安全生产具有一定参考价值。

Heavy metal pollution in rice fields has become one of the main threats to China’s food security.[Objective]Astragalus sinicusL.(Chinese milk vetch)is the main green manure crop for rice cultivation in southern China.This paper studies the effects of chemical fertilizer combined with biochar on rice yield and the absorption,migration and accumulation of cadmium(Cd)in rice under the condition of rolling Chinese milk vetch into the soil.[Method]In this study,a pot experiment was adopted.Four biochar addition levels were set under the condition of subsfituting Chinese milk vetch for 30% of nitrogen fertilizer[CK(0 control),C25(2.5 g/kg),C50(5 g/kg),C100(10 g/kg)],to study and analyze the effects of different application amounts of biochar on rice growth and cadmium(Cd)migration and accumulation.[Results]The surface of biochar has a number of irregular spherical protrusions,and a small amount of debris is attached to the surface of these spherical protrusions.In addition,the biochar itself contains many oxygen-containing functional groups such as hydroxyl,carbonyl and carboxyl groups. The dry matter quality of rice organs was significantly improved under the conditions of applying biochar.In the treatments of C50,C25 and C100,there were significant differences in the dry matter quality of rice organs.The dry matter quality of rice roots treated with C50 was significantly higher(P<0.05)than that treated with C25 and C100,increasing by 30.9% and 44.4%,respectively.At the same time,the dry matter quality of rice straw and grains was significantly higher(P<0.05)than that in the two treatments of CK and C100,the dry matter quality of rice straw increased by 14.3% and14.1%,respectively,and the dry matter quality of rice grains increased by 52.5% and 26.3%,respectively.Compared with no addition of biochar,the application of biochar increased the yield of rice grains significantly.Among them,the biochar addition amounts of 25 g/kg and 50 g/kg increased the yield of rice grain significantly,increasing by 52.5% and 33.7%,respectively.In addition,the application of biochar reduced the cadmium(Cd)content in rice grains,and the cadmium contents in the C25,C50,and C100 treatment groups decreased by 13.2%,14.1% and 11.0% respectively compared with that in the control.It can be concluded that biochar can inhibit the transport of cadmium(Cd)in various organs of rice,and the transport coefficients of all transport processes reduced.Compared with the control group,the reduction range of TF aboveground part/root was5%-11.6%,the reduction range of TF stalk/root was 1.5%-10.4%,and the reduction range of TF grain/stalk was 6.1%-12.1%.[Conclusion]In summary,since biochar has a large specific surface area and a variety of oxygen-containing functional groups,it can effectively passivate heavy metals in the soil.Besides,the addition of biochar under the condition of rolling Chinese milk vetch into the soil can not only increase rice yield,but also effectively reduce the cadmium(Cd)content in rice grains and inhibit the transport of cadmium(Cd)to rice grains.Therefore,this fertilization scheme has some reference value for the safe production of rice in cadmium(Cd)contaminated soil.