Characteristics of Greenhouse Gas Emissions from Yellow Paddy Soils under Long-Term Organic Fertilizer Application

Abstract

Reducing greenhouse gas emissions from rice fields is essential to respond to the national “dual-carbon” strategy, achieve green agricultural development, and ensure food security. The substitution of organic fertilizers for chemical fertilizers is an important means to achieve zero growth and has a positive impact on crop yield and soil nutrients; however, the impact on the greenhouse effect is inconsistent. The effects of organic fertilizers on soil greenhouse gas emissions vary depending on factors such as soil, geography, ecological environment, and human management. However, previous research has shown that the combined application of organic fertilizer can increase soil carbon storage and increase crop yield, and may be an effective fertilization measure to reduce greenhouse gas emissions from yellow paddy fields. To clarify the effects of different ratios of organic fertilizer on the greenhouse gas emission characteristics of Guizhou yellow paddy soil, CH4, CO2, and N2O emissions from rice fields were monitored by static opaque chamber-gas chromatography, and the effects of different fertilization treatments on the cumulative greenhouse gas emissions and global warming potential (GWP) were investigated. Results showed that organic fertilizer application increased CH4 emissions from rice fields, and the effect increased with increasing organic fertilizer application. The peak period was from the heading stage to the filling and ripening stage, and there was almost no emission during the fallow period. Compared with the balanced application of chemical fertilizer (NPK), the treatment with organic fertilizer alone (M) significantly increased CO2 emissions, but the replacement of 1/2 chemical fertilizer nitrogen with 1/2 organic fertilizer (1/2 M + 1/2 N-PK) and the replacement of 1/4 chemical fertilizer nitrogen with 1/4 organic fertilizer (1/4 M + 3/4 N-PK) did not significantly increase CO2 emissions; emissions were 5% lower in the 1/2 M + 1/2 N-PK treatment than in the NPK treatment. Compared with the NPK treatment, the application of organic fertilizer alone significantly reduced N2O emissions by 32.16%, while the 1/2 M + 1/2 N-PK and 1/4 M + 3/4 N-PK treatments increased N2O emissions by 6.31% and 16.02%, respectively. However, there were no significant differences between the organic–inorganic combined treatments and NPK. During the flooding period, N2O emissions were relatively low, but the emissions increased rapidly after field drying. The application of organic fertilizer increased the GWP of rice fields. Compared with the NPK treatment, the M treatment increased GWP by 47.07%, 1/2 M + 1/2 N-PK increased GWP by 10.16%, and the 1/4 M + 3/4 N-PK treatment increased GWP by 2.93%. Except for the M treatment, the differences between treatments were not significant. Our results concluded that replacement of chemical fertilizers with organic fertilizers at a ratio of 1/4 to 1/2 did not significantly increase greenhouse gas emissions in rice fields, besides, it mitigate the greenhouse effect and increase soil carbon sequestration and yield in rice fields.