To evaluate long-term effect of biochar application on yield-scaled greenhouse gas emissions (YSGE) in a paddy rice cropping system, a 4-year field experiment by static chamber - gas chromatograph ...method was conducted in South China. Principal component analysis and terminal restriction fragment length polymorphism (T-RFLP) and real-time qPCR was used to unravel the microbial mechanisms of biochar addition. Six treatments were included: control (CK), application of 5tha−1 biochar (BC1), application of 10tha−1 biochar (BC2), application of 10tha−1 biochar (BC3), rice straw return at 2400kgha−1(RS) and inoculated rice straw return at 2400kgha−1(RI). The results indicated that biochar amendment significantly decreased methane (CH4) and gross greenhouse gas (GHG) emissions. This may primarily be ascribed to the stimulated biodiversity and abundance of methanotrophic microbes, increased soil pH and improved aeration by reducing bulk density after biochar incorporation. Compared with CK, RS and RI, 26.18%, 70.02%, 66.47% of CH4 flux and 26.14%, 70.16%, 66.46% of gross GHG emissions were reduced by biochar (mean of three biochar treatments), respectively. Furthermore, biochar significantly increased harvest index of double rice production (p<0.05). In comparison with CK, RS and RI, 29.14%, 68.04%, 62.28% of YSGE was reduced by biochar, respectively, and the highest biochar addition rate (20tha−1) contributed most to the mitigation of GHG emissions (36.24% decrease compared to CK) and improvement of rice yield (7.65% increase compared to CK). Results of our study suggested that long-term application of biochar should be the potential way to mitigate GHGs emissions and simultaneously improve rice productivity in the paddy rice system.
Relative change ratio of different biochar amendments and rice straw residues to CK treatment during the rice growing seasons from 2012 to 2015.
* and *** stand for significant at 0.05 and 0.001 probability level, respectively. Display omitted
•Biochar addition significantly reduced YSGE in paddy rice field.•Biochar stimulated biodiversity and abundance of methanotrophic microbes.•Biochar increased soil pH and aeration by reducing soil bulk density.•Genetic techniques excavated the microbial mechanisms of biochar effect.•Long-term effect of biochar favors both food security and low carbon agriculture.
The combined impacts of modified nitrogen (N) fertilizers and water saving irrigation (WSI) on greenhouse gas (GHG) emissions and grain yield of rice paddies have not previously been documented. GHG ...emissions from rice paddies under modified N fertilizers and WSI deserve attention because water and N are being used extensively to attain higher grain yield. A field experiment was conducted to evaluate the influence of modified N fertilizers and WSI on methane (CH4) and nitrous oxide (N2O) emissions and grain yield in rice paddies. Four treatments were applied: urea with conventional irrigation (U+CI), urea with shallow water depth with alternate wetting-drying water saving irrigation (U+SWD), polymer-coated controlled release urea with SWD (CRU+SWD), and nitrapyrin-urea composition plus hydroquinone with SWD (NU+HQ+SWD). Compared to U+CI, CH4 emissions significantly decreased by 26% and 31%, and N2O emissions increased by 52% and 42% under U+SWD in the early and late rice growing seasons respectively (p<0.05). Although SWD increased N2O emissions, total GHG emissions (TGHG) reduced by 20% and 25% in the two rice seasons under U+SWD, and GHG emission intensity (GHGI) decreased by 24% on average. Modified N fertilizer applications also affected grain yield and GHG emissions under SWD. Compared with U+SWD, CRU+SWD and NU+HQ+SWD reduced CH4, N2O emissions and TGHG by 28–49%, 12–44% and 26–45%, respectively, while grain yield increased by 6–35%. Reduction in CH4 emissions occurred because, compared to urea, CRU and NU+HQ can inhibit CH4 production and transport by controlling development of invalid tillers, while their nitrogen release patterns were more favorable for CH4 consumption. In summary, modified N fertilizers in combination with SWD are a win-win strategy to improve grain production while reducing GHG emissions in the rice cropping system.
•Water saving irrigation significantly reduced CH4 and total GHG emissions in rice paddies.•Modified N fertilizers significantly reduced CH4 emissions by influencing CH4 production, oxidation, and transport.•Combination of water saving irrigation and modified N fertilizers further reduce GHG emissions while improving rice yield.
Assessment of indirect emission factors (EF5r) of nitrous oxide (N2O) from agricultural river networks remains challenging, and results are uncertain due to limited data availability. This study ...compared two methods of assessing EF5r using data from long-term observations at high temporal resolution in a typical agricultural catchment in subtropical central China. The concentration method (method 1) and the Intergovernmental Panel on Climate Change (IPCC) 2006 method (method 2) were employed to evaluate the emission factor. EF5r estimated using method 1 (i.e., EF5r1) was 0.00077 ± 0.00025 (0.00038–0.00097). EF5r calculated using method 2 (i.e., EF5r2) was lower than EF5r1, with a mean value of 0.00004 (0.000015–0.00012). Both EF5r1 and EF5r2 were significantly lower than the IPCC 2006 default value of 0.0025, suggesting that N2O emissions from China and world river networks may be grossly overestimated. A complex N2O production pathway and diffusion mechanism were responsible for the transfer of N2O from the sediment to river water and then to the atmosphere. These findings provide essential data for refining national greenhouse gas inventories and contribute evidence for downward revision of indirect emission factors adopted by the IPCC.
Based on the remote sensing and meteorological data collected from the 1981-2004 period, we calculated the alpine grassland Net Primary Productivity (NPP) in Northern Tibet using the ...Carnegie-Ames-Stanford Approach (CASA), and subsequently analyzed the trend of grassland NPP changes and its response to climate change from 1981 to 2004. The results show that alpine grassland NPP in Northern Tibet was very low in the last 24 years with a relatively large yearly variation. Most of the grassland area (88.61%) in Northern Tibet did not show a significant annual NPP change. The area with a significant decrease of annual NPP variation accounted for only 11.30% of the total grasslands surface, whereas that with a significant increase accounted for 0.09%. In recent years, the precipitation variation in Northern Tibet resulted in an increase of grassland NPP, though solar radiation resulted in decreased grassland NPP. During the 1981-2004 period, total solar radiation, precipitation and temperature, with a decreasing impact magnitude factor, have impacted the grassland NPP in Northern Tibet. The impact of regional climate change on grassland NPP was overall more detrimental than positive.
The kiwifruit (Actinidia arguta var. purpurea) produces oval shaped fruits containing a slightly green or mauve outer exocarp and a purple-flesh endocarp with rows of tiny black seeds. The flesh ...color of the fruit results from a range of anthocyanin compounds, and is an important trait for kiwifruit consumers. To elucidate the molecular mechanisms involved in anthocyanin biosynthesis of the sarcocarp during A. arguta fruit development, de novo assembly and transcriptomic profile analyses were performed. Based on significant Gene Ontology (GO) biological terms, differentially expressed genes were identified in flavonoid biosynthetic and metabolic processes, pigment biosynthesis, carbohydrate metabolic processes, and amino acid metabolic processes. The genes closely related to anthocyanin biosynthesis, such as phenylalanine ammonia-lyase (PAL), chalcone synthase (CHS), and anthocyanidin synthase (ANS), displayed significant up-regulation during fruit development according to the transcriptomic data, which was further confirmed by qRT-PCR. Meanwhile, a series of transcription factor genes were identified among the DEGs. Through a correlation analysis. AaMYB1 was found to be significantly correlated with key genes of anthocyanin biosynthesis, especially with CHS. Through a transient expression assay, AaMYB1 induced anthocyanin accumulation in tobacco leaves. These data provide an important basis for exploring the related mechanisms of sarcocarp anthocyanin biosynthesis in A. arguta. This study will provide a strong foundation for functional studies on A. arguta and will facilitate improved breeding of A. arguta fruit.
Farmed animals produce excrement containing excessive amounts of toxic heavy metals as a result of consuming compound feed as well as receiving medical treatments, and the presence of these heavy ...metals may aggravate the risk of spreading drug-resistance genes through co-selection during manure treatment and application processes. However, research on the association between heavy metals and antimicrobial resistance is still lacking. In this study, metagenomic sequencing was used to explore the effects of the co-selection of environmentally toxic heavy metals on the resistome in manure. A relevance network analysis showed that metal-resistance genes (MRGs), especially for copper (Cu) and zinc (Zn), were positively correlated with multiple types of antibiotic-resistance genes (ARGs) and formed a complex network. Most bacteria that co-occurred with both MRGs and ARGs simultaneously are members of Proteobacteria and accounted for 54.7% of the total microbial species in the relevance network. The remaining bacteria belonged to Firmicutes, Bacteroidetes and Actinobacteria. Among the four phyla, Cu- and Zn-resistance genes had more complex correlations with ARGs than other MRG types, reflecting the occurrence of ARG co-selection under the selective pressure of high Cu and Zn levels. In addition, approximately 64.8%, 59.1% and 68.4% of MRGs that correlated with the presence of plasmids, viruses and prophages, respectively, are Cu- or Zn-resistant, and they co-occurred with various ARGs, indicating that mobile genetic elements participate in mediating ARG co-selection in response to Cu and Zn pressure. The results indicated that the use of heavy-metal additives in feed induces the increases of drug resistance genes in manure through co-selection, aggravating the risk of antimicrobial resistance diffusion from animal farm to manure land applications.
•Heavy metals facilitate ARG proliferation in manure through co-selection.•Heavy metal level determines the complexity of MRG–ARG co-occurrence pattern.•Bacterial preference occurs in ARG co-selection induced by heavy metals.•Proteobacteria are primary resistance gene carriers affected by co-selection.•Cu and Zn trigger wider responses of resistance than other heavy metals.
Pseudomonas syringae pv. actinidiae (Psa), a bacterial pathogen, is a severe threat to kiwifruit production. To elucidate the species-specific interaction between Psa and kiwifruit, ...transcriptomic-profiles analyses were conducted, under Psa-infected treatment and mock-inoculated control, on shoots of resistant Maohua (MH) and susceptible Hongyang (HY) kiwifruit varieties. The plant hormone-signal transduction and plant–pathogen interaction were significantly enriched in HY compared with MH. However, the starch and sucrose metabolism, antigen processing and presentation, phagosome, and galactose metabolism were significantly enriched in MH compared with HY. Interestingly, the MAP2 in the pathogen/microbe-associated molecular patterns (PAMPs)-triggered immunity (PTI) was significantly up-regulated in MH. The genes RAR1, SUGT1, and HSP90A in the effector-triggered immunity (ETI), and the NPR1 and TGA genes involved in the salicylic acid signaling pathway as regulatory roles of ETI, were significantly up-regulated in HY. Other important genes, such as the CCRs involved in phenylpropanoid biosynthesis, were highly expressed in MH, but some genes in the Ca2+ internal flow or involved in the reactive oxygen metabolism were obviously expressed in HY. These results suggested that the PTI and cell walls involved in defense mechanisms were significant in MH against Psa infection, while the ETI was notable in HY against Psa infection. This study will help to understand kiwifruit bacterial canker disease and provide important theoretical support in kiwifruit breeding.
Editorial on the Research Topic Agricultural non-point source pollution and greenhouse gas: emission, control, and management The migration and transformation of carbon (C), nitrogen (N) and ...phosphorus (P) in agroecosystems play an important role in global climate change, food security, and environmental protection and sustainability. ...there is a pressing need to explore options to removing ammonia from the environment. Water 5, 59. doi:10.1038/s41545-022-00202-0 www.frontiersin.orgLiang Zhang1,2, www.frontiersin.orgHongbin Liu3, www.frontiersin.orgXiaobo Qin4 and www.frontiersin.orgJian Liu5* * 1Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan, China * 2University of Chinese Academy of Sciences, Beijing, China * 3Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, Beijing, China * 4Institute of Environment and Sustainable Development in Agriculture, Chinese Academy of Agricultural Sciences, Beijing, China * 5Department of Soil and Land Use, Norwegian Institute of Bioeconomy Research, Ås, Norway
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