Green Manuring with Oilseed Rape Emissions in a Rice-Ratooning System in Central China

• Published in: Agriculture (Basel) Vol. 14; no. 6
• Main Authors: Yao, Lai, Zhu, Jie, Yang, Wei, Zhao, Dongzhu, Zhou, Yong, Li, Shaoqiu, Nie, Jiangwen, Yi, Lixia, Liu, Zhangyong, Zhu, Bo
• Format: Journal Article
• Language: English
• Published: MDPI AG 01-06-2024
• Subjects: Air pollution; Greenhouse gases; Methane; Nitrous oxide; Organic fertilizers; China
• ISSN: 2077-0472; 2077-0472
• DOI: 10.3390/agriculture14060839

The use of oilseed rape (OS, Brassica napus L.) as a winter green manure is crucial for enhancing soil fertility and reducing chemical N application in paddy fields. However, the impacts of replacing varying amounts of chemical N with OS on CH[sub.4] and N[sub.2]O emissions in paddy soils have not been well evaluated. In this study, GHG emissions, soil properties and OS decomposition in a rice-ratooning system with different OS-urea N replacement rates (0%, 25%, 50%, 75% and 100%) were investigated. Our results indicate that 84.7–90.7% of the initial C and 97.5–98.4% of the N were released during the 192-day decomposition process, and that the mineralization patterns of net C and net N in the OS residue were consistent with a single exponential decay model. The lowest CH[sub.4] emissions (9.97 g m[sup.−2]) were observed at 0% OS, while the highest N[sub.2]O emissions (0.40 g m[sup.−2]) were observed at this level of substitution. Conversely, the highest CH[sub.4] emissions (20.71 g m[sup.−2]) and lowest N[sub.2]O emissions (0.07 g m[sup.−2]) were observed at 100% OS. Compared to 0% substitution, 25% substitution significantly decreased GWP and GHGI without reducing rice grain yield. Environmental parameters such as soil redox, NH[sub.4] [sup.+]-N and residual N and C were shown to be significantly associated with CH[sub.4] emissions, whereas soil redox, NH[sub.4] [sup.+]-N and residual C were the main drivers of N[sub.2]O emissions. In conclusion, 25% substitution of OS was the most cost-effective measure for balancing greenhouse gas emission and rice yield.