广西典型岩溶地区硒在土壤-农作物系统中累积特征及其影响因素

Accumulation characteristics and influencing factor of selenium in soil-crop system in typical karst area of Guangxi

为查明硒在岩溶区土壤-农作物系统中累积特征及其影响因素,系统采集了广西典型岩溶区大新县农作物及其配套根系土232组,分析测定了土壤和农作物中Se、Al_(2)O_(3)、Fe_(2)O_(3)、Corg等含量。结果表明,研究区根系土点位富硒率为92%,成土过程中岩溶区土壤硒主要受自然理化性质的影响,成土母岩对其影响逐渐减弱。农作物Se含量变化范围为0.003~0.24 mg/kg,平均值为0.034 mg/kg,变异系数为102.83%,100%的玉米、55%的早稻、49%的晚稻达到富硒标准,不同农作物硒含量差异明显,主要受地质背景、作物种类等因素影响,玉米和水稻中硒含量显著高于香蕉、龙眼和柑橘,土壤-玉米系统中硒的迁移能力显著强于其他农作物系统。相关分析表明,根系土Se与Al_(2)O_(3)、Fe_(2)O_(3)、Corg呈显著正相关,与K2O、MgO、CaO、pH值显著负相关。农作物籽实中Se含量与根系土Mo、Cr、As、Ge、Fe_(2)O_(3)、Al_(2)O_(3)呈负相关,表明根系土中铁铝等黏土矿物不利于农作物吸收硒;与根系土pH值、SiO_(2)呈正相关,表明砂质土壤和中碱性土壤利于农作物吸收硒。

In order to find out the accumulation characteristics and influencing factor of Se in the soil-crop system in the karst area,232 group samples of crops and rhizosphere soils in Daxin County,a typical karst area of Guangxi,are systematically collected,and the contents of Se,Al_(2)O_(3),Fe_(2)O_(3) etc.in soils and crops are analyzed.The study result shows that the selenium-enriched rate of the rhizosphere soils in study area is 92%.During the pedogenesis,the selenium content of soil in the karst area is mainly affected by the natural physical and chemical properties with decreasing influence by the pedogenic parent rock.The variation range of selenium content in crops is 0.003-0.24 mg/kg with the average value of 0.034 mg/kg and the coefficient of variation is 102.83%.100%corn,55%early rice and 49%late rice reach the standard of selenium enrichment.The selenium contents of different crops vary significantly,mainly affected by the factors such as geological background and crop types.The selenium content in corn and rice is significantly higher than that in banana,longan and citrus.The transfer ability of selenium in soil-corn system is stronger than that in other systems.Correlation analysis demonstrates that the rhizosphere soil Se is significantly positively correlated with Al_(2)O_(3),Fe_(2)O_(3),and Corg and it is significantly negatively correlated with K2O,MgO,CaO and pH.It is shown that the clay minerals involving iron and aluminum in the root soil are not conducive to the absorption of selenium by crops.The content of Se in crop seeds is negatively correlated with Mo,Cr,As,Ge,Fe_(2)O_(3) and Al_(2)O_(3),and positively correlated with pH and SiO_(2) in root soil,indicating that sandy soil and moderately alkaline soil are favorable for crops to absorb selenium.