硅肥等量施用对土壤镉生物有效性和水稻吸收镉的影响

为研究硅（Si）肥等量施用对水稻不同生育期吸收镉（Cd）和土壤Cd生物有效性的影响，采用5种不同种类的Si肥（SiO₂用量为225 kg ·hm^-2）开展田间小区试验.结果表明，随着水稻生育期的延长，水稻根系和茎叶的Cd含量增加；施用Si肥，不同生育期水稻根系、茎叶和籽粒Cd含量平均分别降低14.9%、28.2%和12.2%；硅钙镁铁肥（SiCaMgFe）和水溶Si肥（SiW）处理，籽粒Cd含量分别比对照处理降低21.1%（P<0.05）和21.2%（P<0.05）；水稻根表铁膜中Cd含量（DCB-Cd）随着水稻生育期延长而增加，施用Si肥，水稻不同生育期DCB-Cd含量有高有低，DCB-Cd是根系Cd含量的15.8%~42.8%；与对照相比，施用Si肥水稻成熟期土壤可交换态Cd （Exc-Cd）含量平均降低36.4%，其它形态的含量平均增加12.5%~48.2%.水稻全生育期根系Cd与Si呈极显著负相关，与DCB-Cd呈极显著正相关，DCB-Cd与土壤有效态Cd和有效态Si呈极显著负相关，土壤Exc-Cd与Carb-Cd呈极显著负相关，土壤有效态Cd与pH值呈显著负相关.施用相同Si肥用量，SiCaMgFe和SiW处理降低水稻Cd含量的效果好；施用Si肥通过提高土壤pH值和土壤有效Si含量、降低土壤有效态Cd和Exc-Cd含量，促进Exc-Cd向Carb-Cd转移，减少根表铁膜对Cd的吸附，从而减少水稻对土壤Cd的吸收.

Effects of Equal Amounts Silicon Fertilizer Application on Soil Bioavailability of Cadmium and Cadmium Uptake by Rice

Cadmium (Cd) contamination of paddy fields is a global concern, as it can cause the accumulation of Cd in food. To explore the effects of equal application of silicon fertilizers on the bioavailability of cadmium and soil Cd uptake at different growth stages of rice, a field experiment was conducted with five silicon fertilizers under the same silicon dose (225 kg·hm^-2). The results revealed that the Cd contents in roots, stems, and leaves increased with the extension of the rice growth stage. The application of silicon fertilizers reduced the Cd contents in roots, stems, and leaves in brown rice by 14.9%, 28.2%, and 12.2%, respectively. Compared with that in the control, the Cd content of brown rice in the SiCaMgFe and SiW treatments was decreased by 21.1% (P<0.05) and 21.2% (P<0.05), respectively. Similarly, Cd content in iron plaque (DCB-Cd) increased with the extension of the rice growth period, which accounted for 15.8%-42.8% of the total Cd content in roots, and the DCB-Cd content was different in each stage of rice. The content of exchangeable Cd (Exc-Cd) in soil at the mature stage of rice decreased by 36.4%, and the other fractions increased by 12.5%-48.2%. The results showed significant negative correlations between the Cd contents and Si in roots, DCB-Cd and soil available Cd and available Si, Exc-Cd and Car-Cd, and soil available Cd and pH value. Cd content in roots was positively correlated with DCB-Cd. With the equal dose of silicon fertilizer, the treatments of SiCaMgFe and SiW could effectively reduce the Cd content in rice. The application of silicon fertilizer promoted the transfer of Exc-Cd to Carb-Cd by increasing the soil pH value and the soil available Si content, meanwhile reducing the soil available Cd, Exc-Cd contents, the adsorption of Cd by the iron film on the root surface, and the adsorption capacity of iron plaque and root, thereby reducing the absorption of Cd by rice.