Nitrification inhibitors,HQ, DCD and TU, could all decrease nitrate contents in pakchoi significantly in three stages of pakchoi. But the effect varies with the test soil.

• 三种硝化抑制剂HQ(氢醌)、DCD(双氰胺)和TU(硫脲)在蔬菜的不同时期均不同程度的降低了蔬菜硝酸盐含量，但是不同供试土壤上的试验反映的情况不完全一致。