通过培养试验,研究了普通尿素(PU)、硫包膜尿素(SCU)和树脂包膜尿素(PCU)在最大田间持水量(湿润)和60%田间持水量(适宜湿度)对污染土壤Cd有效性的影响.结果表明,不同水分条件下包膜尿素对土壤Cd有效性的影响差异显著.培养60d后水溶态Cd含量最大田间持水量下均显著低于60%田间持水量下.最大田间持水量下施用PU、SCU和PCU均降低了水溶态Cd含量,降低程度为PCU>PU>SCU；施用SCU和PCU均降低了有效态Cd含量,降低程度为SCU>PCU.60%田间持水量下施用PU和PCU均降低了水溶态Cd含量,降低程度为PU>PCU；施用PU、SCU和PCU均降低了有效态Cd含量,降低程度为PCU>PU>SCU.不同控释尿素和水分含量对水溶态Cd的影响较有效态 Cd 的影响更加突出.最大田间持水量下水溶性 SO42-含量与有效态 Cd 含量呈显著正相关；60%田间持水量下铵态氮含量与水溶态Cd含量呈显著负相关,硝态氮含量与有效态Cd含量呈显著负相关.在Cd污染的酸性土壤旱作中,湿润状态下宜施用SCU,适宜湿度下宜施用PCU,以降低土壤Cd的有效性.%The effects of prilled urea (PU), sulfur coated urea (SCU) and polymer coated urea (PCU) on Cd availability in contaminated soil under two different moisture conditions-maximum water holding capacity (water holding capacity, WHC, noted as humid condition) and 60% of WHC (noted as suitable humid condition) was investigated through incubation experiment. The results showed that the application of different coated nitrogen fertilizer under different moisture conditions significantly affect the availability of Cd. The concentration of water-soluble Cd at maximum WHC were significantly lower than those at 60%WHC after 60 days cultivation. Under maximum WHC condition, compared with the control, the concentrations of water-soluble Cd of the treatments with PU, SCU and PCU decreased in the order of PCU>PU>SCU, while the concentrations of available Cd of the treatments with SCU and PCU decreased in the order of SCU>PCU. Under 60% WHC condition, compared with the control, the concentrations of water-soluble Cd of the treatments with PU and PCU decreased, showing the order of PU>PCU, and the concentrations of available Cd of the treatments with PU, SCU and PCU also decreased, showing the order of PCU>PU>SCU. The application of different coated nitrogen fertilizer under different moisture conditions has a more remarkable effect on water-soluble Cd concentration than available Cd concentration. Furthermore, under maximum WHC condition, water-soluble SO42-concentration had significant positive correlation with available Cd concentration. However, under 60%WHC condition,the concentration of ammonium nitrogen was significantly negatively correlated with water-soluble Cd concentration, and the concentration of nitrate was significantly negatively correlated with available Cd concentration. The results further suggested that under dry farming operation in the Cd contaminated acid soil, SCU could be adopted in humid condition, while PCU be adopted in suitable humid condition, which could effectively lower availability of Cd in soil.
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