石灰及配合施用镁和硅对土壤pH和镉有效性的影响

Effects of Lime and Its Combination with Magnesium Sulfate and Sodium Silicate on Soil pH and Cd Availability

【目的】为了研究在低浓度镉污染土壤上,施用不同量石灰以及石灰与镁、硅配合施用对土壤pH和镉有效性的影响,寻求降低土壤中镉生物有效性或毒性的有效实用技术措施。【方法】本研究分室内小量土壤(10g)培养试验和模拟田间的较大量土壤(1.5kg)网室培养试验,试验设置对照、4个石灰用量、4个石灰用量加镁和4个石灰用量加硅,共13个处理6次重复,淹水培养60d(室内)和120d(网室)并定期测定土壤pH和有效镉的变化规律。【结果】淹水后所有处理的土壤pH都随培养时间的延长而向中性趋近,初始pH越高的处理其最终pH降幅也越大。土壤有效镉含量的变化与土壤pH呈负相关。所有处理土壤有效的含量都低于或显著低于对照,不同物料和组合对土壤有效镉含量的降低效果依次为石灰+Si>石灰+Mg>石灰,高量石灰处理明显优于低量石灰处理,石灰配施镁或硅能进一步降低土壤中镉的有效性。【结论】施用石灰能有效降低土壤镉的有效性,在石灰的基础上配合施用硅或镁的效果更佳。

[ Objective ] The objectives of the experiments were to investigate effects of different rates of lime and its combination with magnesium sulfate （Mg） and sodium silicate （St） on soil pH and available cadmium （Cd） and to further seek some applicable agronomic practices to reduce bioavailability of Cd in the Cd contaminated soils. [ Method] The study included an in-lab incubation experiment with log soil and an in-net house incubation experiment with 1.5 kg soil to simulate what could happen in the field, both experiments consisted of 13 treatments and six replications including CK, four rates of lime, four rates of lime ＋ Mg and four rates of lime ＋ Si incubated under waterlogged condition for 60 d （in-lab） and 120 d （ in-net house） , and soil pH and available Cd of each treatment were measured periodically. [ Result]The soil pH was always approaching to neutrality for any treatment after flooding. The higher the initial pH, the greater decline of the final pH was. There was a negative correlation between soil available Cd and soil pH. All the treatments had significant lower available Cd than the control. The treatment effects on soil available Cd followed an order of lime ＋ Si 〉 lime ＋ Mg 〉 lime, and the higher the lime rates the better the effect. On the basis of lime application, addition of Mg or Si could further effectively reduce contents of soil available Cd. [ Conclusion ] Application of lime can effectively reduce amounts of soil available Cd, while addition of Si or Mg on the basis of lime is even more effective than using lime alone to reduce availability of soil Cd.