Abstract: This study aims at exploring the nitrous oxide (N₂O) emissions and key impact factors under alternative organic fertilizer substitution managements from Guangdong province, which has hot and rainy climate, acidic soils, and high multiple cropping index cultivation. We conducted one year in situ observations (from November 22, 2022, to December 3, 2023) by using the static opaque chamber method. Flowering Chinese cabbage (P1), lettuce (P2), sweet corn (P3) and flowering Chinese cabbage (P4) were cultivated in turn in this study. Five treatments were implemented: only chemical fertilizer application (R), substitution 15% and 30% of chemical fertilizer nitrogen with commercial organic fertilizer (M15% and M30%), substitution 15% of chemical fertilizer nitrogen with composted vegetable residue (S15%), and no nitrogen fertilizer application (CK). The results show there was no significant difference in crop yield between organic fertilizer replacement treatment and R treatment. During the whole observation period, the peak of N₂O emission of each nitrogen application treatment generally occurred within 2 ~ 6 days after the irrigation event, and the N₂O emission flux of each treatment ranged from 2.85 ~ 2446.49 μg N₂O m^-2 h^-1. The annual N₂O emission of R treatment was 2.66 kg N hm^-2 , and the N₂O emission of each organic fertilizer treatment increased by 25.56% ~ 52.25%. The total N₂O emissions of P1, P2, P3, P4 were 0.22, 0.30, 1.24, 0.35 and 0.55 kg N hm^-2, respectively, they accounted for 8.13%, 11.37%, 46.69%, 13.31% and 20.50% of the total annual emissions respectively. There was no significant difference between substituting organic manure for compound treatments and R treatment in seasonal emissions for P1 and P2. Seasonal emissions were higher in substituting organic manure for compound treatments than that in R treatment for P3, and which were lower for P4(P < 0.05). The annual N₂O emission factors ranged from 0.15% to 0.31% . The mean N₂O emission flux increased with the increase of soil temperature, and there was a significant negative correlation between N₂O emission flux and WFPS (P < 0.05). N₂O emission peak appeared with high soil NO₃^--N contents. Under patterns of grain and vegetable rotation in Guangdong province, organic fertilizer substitution managements increased annual N₂O emissions, but they had different impacts on seasonal N₂O emissions. Nitrogen fertilizer application, type of organic fertilizer, soil temperature and moisture were identified as primary factors influencing soil N₂O emissions.