Abstract: A field experiment was conducted on two soil types in the Changsha suburb of Hunan Province to study the effects of hydroquinone (HQ),dicyandiamide (DCD) and thiourea (TU) on the nitrate content in soil and pakchoi and on the yield of pakchoi.The results showed that all the test nitrification inhibitors could significantly decrease the nitrate content in soil and pakchoi during whole growth stage,among which,DCD had the best effect,but the effect was differed on different soil types.Nitrification inhibitors could increase pakchoi yield,DCD was also the best one,and the effect was significantly better on vegetable garden red soil than on vegetable garden alluvial soil.The nitrate content in soil and pakchoi was the highest about 40 days after pakchoi transplanting.

Key words: Sacred groves, Yi nationality, Chuxiong, Biodiversity conservation