脲酶抑制剂/硝化抑制剂对植稻土壤中尿素N行为的影响

采用自制根盒试验，主要研究了脲酶抑制剂氢醌（HQ），硝化抑制剂双氰胺（DCD）及二者组合对离水稻根际不同距离处NH4^--N和NO3^-N分布的影响，结果表明，DCD及其与HQ组合均能显著促进稻株地上部分生长，始终显著降低水稻根际与近根际土中NH4^ -N含量直至施肥后60d，施肥后20d时，DCD及其与HQ组合可使非根际土中NH4^ -N含量显著增加，随后，却出现相反现象，施肥后20d时，距根际不同距离的土壤中，配施DCD或DCD＋HQ处理均能显著降低NO3^-N含量，随后，近根际和非根际仍保持上述现象直至施肥后40d；同未施DCD处理相比，根际土壤却较早出现NO3^--N含量高峰，正好与水稻N营养需求时期相一致，因此，DCD及其与HQ组合可减少水稻根际环境下尿素N损失潜势，通过不种稻土壤和距根际3cm处的土壤中尿素无机氮形态分布的差异，充分显示了研究水稻根际土壤氮素转化及相关抑制剂对其影响时，以取离根际3cm外的土壤作为非根际明显优于不种稻土壤。

Effect of urease/nitrification inhibitors on the behavior of urea-N in the soil planted to rice

The influences of urease/nitrification inhibitors on urea-derived ammonium and nitrate contents in the soils at increasing distances from rice root rhizosphere were studied by a self-made rhizobox.The results showed that dicyandiamide (DCD) with or without hydroquinone (HQ) significantly improved the growth of rice during the period of cultivation, and decreased the urea-derived ammonium contents in rhizosphere and near rhizosphere soil until 60 days after fertilization.Treatments with DCD and with DCD plus HQ,could remain a much higher ammonium levels in rice non-rhizosphere soil at day 20 after fertilization than the control,but a contrary phenomenon was found afterwards.These two treatments significantly decreased nitrate contents in the soils at some distances from rice root rhizosphere at day 20 after fertilization,and later on,the soil out of the rhizobox remained the similar phenomenon until 40 days.In the presence of DCD,nitrate contents in rice root rhizosphere soil appeared much higher levels during an earlier period than the control.This period was just N utilization peak by rice.Hence,DCD and DCD plus HQ could,to some extent,eliminate the potential for urea-derived N loss in rice root rhizosphere soil.The plant-free soil is apparently not a satisfactory control treatment to study the dynamics of ammonium and nitrate in the rhizosphere soil compared to the non-rhizosphere soil(>3 cm from rice rhizosphere).