Search

To gain insight into the microbial mechanisms associated with the replacement of chemical fertilizers with organic or bio-organic fertilizers to mitigate soil nitrous oxide (N 2 O) emissions, we measured N 2 O emissions from greenhouse vegetable soils through field observations and pot experiments. Results showed that organic substitution suppressed N 2 O emissions by reducing soil mineral N content and stimulating the abundance of the nosZII gene. The trade-off effect of bio-organic substitution on N 2 O emissions may be due to the stimulated activity of the AOA-amoA gene, resulting in unfavorable conditions for N 2 O production and thus reduced N 2 O loss. We also linked the inhibitory effect of organic and bio-organic substitution on N 2 O emissions to the increased abundance of key species in bacterial co-occurrence networks represented by Patescibacteria as they were significantly and negatively correlated with N 2 O emissions. However, the mitigation effect of bio-organic substitution on N 2 O emissions was conteracted by an increase in Bacillus abundance due to the direct negative effect of Bacillus on the nosZII gene abundance. These findings suggest that conventional or bio-organic substitution is a promising strategy for alleviating the environmental costs of crop production., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

The fruit has become the third-largest agricultural planting industry after cereals and vegetables in China. Fertilization regimes (e.g., application rate and method) in fruit orchards typically differ from cereal croplands, which would incur a pronounced difference in fertilizer-induced nitrous oxide (N 2 O) emissions between them. However, fertilizer-induced direct N 2 O emissions from orchard fields remain poorly understood. We conducted a field experiment in a peach orchard and a global meta-analysis of N 2 O emissions from fruit orchards. The emission factor (EF) of fertilizer N for N 2 O averaged 0.81%, with a background N 2 O emission of 3.4 kg N ha–1 yr-1 in our field study. A global meta-analysis suggested that the linear regression model was the best to fit N 2 O emissions by fertilizer N input for most fruit types compared to the nonlinear models. When averaging all global data, the linear model projected the EF of N 2 O from orchards to be 0.84%, with the background emission of 1.96 kg N ha–1. The estimate of direct N 2 O derived from the orchard-specific nonlinear model was substantially lower than those from the nonlinear model with global cropland measurements. The fertilizer-induced direct N 2 O emission from Chinese orchards during the 2000s was estimated to be 32–49 Gg N yr–1, equivalent to about 14% of total direct N 2 O emissions from Chinese uplands. Therefore, orchard cultivation constitutes a hotspot of N 2 O emissions in the agricultural sector, and priority should be given to emissions reduction to achieve the transition to climate-smart agriculture. [Display omitted] • N 2 O emissions from global orchards were summarized and meta-analyzed. • N 2 O emission was 32–49 Gg N yr–1 from Chinese orchards during the 2000s. • Orchard cultivation is one of the hotspots of agricultural N 2 O emissions. • Orchard N 2 O emissions were similar to emissions from vegetables and tea cultivation. [ABSTRACT FROM AUTHOR]