硅肥施用对重金属污染土壤甘蔗镉吸收的影响研究初探

Preliminary Study on the Effect of Silicate Fertilizers on Cadmium Absorption by Sugarcane in Heavy Metal Polluted Farmland

长期采用受铁矿尾矿水污染的河水进行灌溉的农田，其土壤存在一定重金属镉污染，且土壤酸化严重，有效硅活性低。甘蔗是需硅量较大的植物，因此在甘蔗种植过程中施用碱性硅肥既可补充硅营养又可通过硅肥控制镉的吸收。本试验通过硅肥不同施用量及基肥、基肥＋追肥的施用方式的比较，结果表明：在甘蔗种植中一次性施用硅肥1500 kg·hm-2，可以使土壤中活性较高的弱酸提取态镉占镉总量的比例从38.45%下降到32.51%，而甘蔗不能利用的残渣态镉的占比从11.19%提高到14.78%；硅肥分为基肥与追肥两次施用的方式，其对土壤镉的形态的影响也存在相似的规律，且变化趋势更加显著，弱酸提取态镉占比从40.93%下降到35.47%，降幅更加显著；同样残渣态镉则随着硅肥施用量的增加而增加，其占比从16.26%增加到22.66%；施用硅肥能有效降低甘蔗汁中镉的含量，从一次性作为基肥施用的结果来看，每公顷施用375~1500 kg硅肥，其蔗汁中镉含量随施肥量增加而下降，从168.54μg·L-1降至57.87μg·L-1，降幅为28.26%~60.30%；蔗渣中镉含量也有相似的变化趋势，从468.36μg·kg-1降至377.77μg·kg-1，降幅为7.86%~19.34%；采用基肥＋追肥施用硅肥，无论是蔗汁还是蔗渣，其镉的含量同样随硅肥施用量的增加而下降，蔗汁镉含量的降幅更大，最高可降81.18%，从而达到降低甘蔗汁及蔗渣中镉含量水平的目的。

Farmland irrigated with river water polluted by acid mine drainage from iron ores will become very acidic, toxic with heavy metals like cadmiums and low availability of silicon for plant growth. Sugarcane plants needs a lot of silicon for better growth, thus application of silicate fertilizers not only adjust the low pH, but also supply sugarcane for with silicon for better growth and suppress its uptake of cadmium. Experiments were carried with different application rates, application methods （basal, basal ＋ dressing） of silicate fertilizers with an aim to evaluating its effects and optimum dose and time of application. Results showed that with the application of 1500 kg·hm-2 silicate fertilizer as basal, Cd availability of weak acidic extractable form decreased from 38.45% to 32.51%, and the residue form increased from 11.19% to 14.78%. Concomitantly, cadmium content in sugarcane juice decreased from 168.54μg·L-1 to 57.87μg·L-1 with a decreasing percentage of 7.86%~19.34% in the case of silicate application of 375~1500 kg·hm-2. Forms changes became more significant in the case of separate application of silicon fertilizer as basal and dressing with Cd availability of weak acidic extractable form decreased from 40.93% to 35.47% and residue form increased from 16.26% to 22.66%. The maximum decrease percentage of Cd content in sugarcane juice was 81.18%. It was concluded that the application of silicate fertilizer would be an effective method to reduce cadmium content in sugar cane plant grown in heavy metal polluted farmland.