Abstract:In order to reveal the effects of long-term application of different chemical nitrogen (N) fertilizers on soil N supply capacity in greenhouse vegetable fields, soil samples were selected from a 15-year vegetable experiment field, and then the effects of long-term N fertilizer dosage on soil N mineralization and nitrification were studied by aerobiotic soil incubation method, in which five N application rates were designed as:no chemical N fertilization (CK), conventional chemical N rate (100%N), and the conventional chemical N rate reduction of 20% (80%N), 40% (60%N) and 60% (40%N), respectively. The results showed that compared with the initial, the mineralized N of CK, 40%, 60%, 80% and 100%N treatments after incubation were 38.9, 44.7, 20.6, -32.7 and -87.6 mg/kg, respectively. The mineralized N of CK, 40%N and 60%N treatments accounted for 2.7%, 2.5% and 1.0% of the total soil N content, respectively. The mineralized N of 80%N and 100%N treatments decreased by 1.3% and 3.1% compared with the initial. The nitrification rates under CK, 40%, 60%, 80% and 100%N treatments were 19.3, 11.2, 4.9, 5.2 and 1.2 mg/(kg soil·d), respectively. Long-term high rate of chemical N input (80%N and 100%N) significantly reduced soil N mineralization and nitrification rates and decreased soil N supply capacity in greenhouse vegetable field. The reduction of soil pH may be one of the reasons for the inhibition of soil mineralization and nitrification. In view of this, the greenhouse vegetable production system should reduce the amount of chemical N rate, and promote scientific and optimal fertilization in order to guarantee the sustainable utilization of vegetable soils.