Vegetable production in Subtropical China is distinguished by excessive nitrogen (N) fertilization, frequent irrigation, and multiple crop rotations in a single year. The aforementioned variables are closely related to soil nitrous oxide (N₂O) and methane (CH₄) emissions. Hence, we conducted a field trial to measure N₂O and CH₄ emissions using static chamber–gas chromatograph. Four treatments were used: control (CK) with no fertilizer, 100% chemical N fertilization (CN), the conventional 30% chicken manure N plus 70%CN (CMN + CN), and 30% chicken manure biochar N plus 70%CN (CMBN + CN). The annual cumulative N₂O emissions reached 12.4, 63.5, 111.8, and 44.1 kg N₂O-N ha⁻¹ for the CK, CN, CMN + CN, and CMBN + CN treatments, respectively. Compared to the CN and CMN + CN treatments, the CMBN + CN treatment reduced N₂O emissions by 35.9%–65.7%, while it simultaneously increased the total vegetable yield by 16.1% compared to the CN treatment. Seven seasons mean N₂O emission factors are 1.3% for CN, 3.8% for CMN + CN, and 0.9% for CMBN + CN. The CH₄ emission was negligible, ranging from 0.07 kg CH₄-C ha⁻¹ for the CK treatment to 0.8 kg CH₄-C ha⁻¹ for the CN treatment. N₂O emissions peaked under the conditions of an interior chamber temperature of around 31.9 °C and the water-filled pore space (WFPS) of the soil being approximately 60%. Future climate change will intensify, triggering higher N₂O emissions from subtropical vegetable fields. CMB can be one of the best substitutes for direct chicken manure application as a soil supplement because it has a beneficial effect on improving vegetable yield and reducing N₂O emissions in Subtropical China.