Abstract:

In agricultural production, the combined application of organic fertilizer and chemical fertilizer is often used to reduce the negative effects of single application of chemical fertilizer, but the unreasonable proportion of organic fertilizer instead of chemical fertilizer can easily lead to crop yield reduction, and the effect of organic fertilizer instead of chemical fertilizer on farmland N₂O emission is not uniform. To explore the impact of organic fertilizers instead of chemical fertilizers on N₂O emissions and crop yields in farmland, the sunflower fields in the Hetao irrigation district of Inner Mongolia were used as the study site. Five fertilization treatments with chemical fertilizer (T0), organic fertilizer replacing 25% (T25), 50% (T50), 75% (T75) and 100% (T100) were set up in the experimental base of Ganzhao temple of Bayannur Academy of Agricultural and Animal Husbandry Sciences in 2023. The N₂O emission was determined by static chamber−gas chromatography. Combined with quantitative analysis of soil carbon and nitrogen indicators, enzyme activity and sunflower yield, the N₂O emission law and its relationship with soil indicators were clarified. Explore the appropriate proportion of organic fertilizer substitution in local sunflower production. The results showed that after additional fertilizer (July 13−August 10) was the peak stage of N₂O emissions. Compared with the T0 treatment, the T25, T50, T75 and T100 treatments significantly reduced the cumulative N₂O emissions from farmland during the growing season by 30%, 45%, 52% and 64% respectively. Compared with T0 treatment, the contents of soil soluble carbon and nitrogen (DOC and DON) were significantly increased by 11%−30% and 38%−53%, respectively. Nitrous oxide reductase (NOS) activity was significantly increased by 11%−32%; nitric oxide reductase (NOR) activity was significantly reduced by 14%−30%. The contents of DOC and DON were significantly correlated with NOS activity, and the content of DON was significantly correlated with NOR activity. The increase in NOS activity and the decrease in NOR activity resulted in a decrease in the cumulative N₂O emission from the farmland. Compared with T0 treatment, the sunflower yield of T25 treatment was significantly increased by 30%, and the sunflower yield of T50 treatment was not significantly reduced, and the N₂O emission intensity of T25 and T50 treatments was lower, which was suitable for the local stable production and emission reduction of organic fertilizer instead of chemical fertilizer fertilization scheme.

Key words: Organic fertilizer instead of chemical fertilizer, Farmland N2O emissions, Enzymatic activity, Sunflower yield