不同氮磷钾肥对土壤pH和镉有效性的影响

采用土壤培养方法研究了不同氮、磷、钾肥对土壤pH和镉有效性的影响。结果表明,在培养60 d时,所有氮肥处理均降低了土壤pH,增加了Cd的提取量;但高量尿素和氯化铵处理土壤pH降低最多,提取的Cd也最多;硫酸铵提取的Cd较对照增加最小。所有磷肥处理均引起土壤pH小幅降低,但对土壤Cd提取量的影响以普钙稍大。3种钾肥处理均降低了土壤pH,其中氯化钾在0 d时提取的Cd在所有钾肥处理中为最高,其提取能力15 d后逐渐消失,试验结束时所有钾肥处理对Cd提取量均低于对照。本研究进一步表明,在土壤Cd含量处于污染临界值附近或已受Cd污染的土壤上,应避免施用高量的酸性肥料如尿素、氯化铵、普钙,以及其他酸性物料。在常用磷、钾肥中,磷酸二铵和硫酸钾在Cd污染土壤上施用更为适合。

Effects of application of nitrogen, phosphorus and potassium fertilizers on soil pH and cadmium availability

A soil incubation experiment was conducted to investigate effects of application of nitrogen (N), phosphorus (P) and potassium (K) fertilizers on availability of soil Cd. Results show that after 60 days of incubation, all the N fertilizer treatments lowered soil pH, and increased the amount of extractable Cd; among them urea of high rate and ammonium chloride displayed the most significant effects, and ammonium sulfate did the least in increasing extractable Cd. All the P fertilizer treatments caused modest reduction of soil pH, but in terms of their effect of increasing extractable Cd, only single superphosphate showed something significant. All the three K fertilizer treatments reduced soil pH; among them potassium chloride increased extractable Cd the most at D0, but the effect waned down after D15. At the end of the experiment, the contents of extractable Cd in all the K fertilizer treatments fell below that in CK. The findings further suggest that it is advisable to avoid application at a high rate of acidic fertilizers, such as urea (after its transformation), ammonium chloride and single superphosphate, and other acidic materials as well, to soils severely polluted with Cd or soils with Cd content close to the threshold value of pollution, and use di-ammonium phosphate and ammonium sulfate instead.