ABSTRACT
We investigated the effects of maize straw and its biochar application on soil organic carbon chemical composition, the abundance of carbon degradation genes (cbhI) and the composition of cbhI gene community in a Moso bamboo forest, to provide the theoretical and scientific basis for enhancing carbon sequestration. We conducted a one-year field experiment in a subtropical Moso bamboo forest with three treatments: control (0 t C·hm-2), maize straw (5 t C·hm-2), and maize straw biochar (5 t C·hm-2). Soil samples were collected at the 3rd and 12th months after the treatment. Soil organic carbon chemical composition, the abundance and community composition of cbhI gene were determined by solid-state 13C NMR, real-time fluorescence quantitative PCR, and high-throughput sequencing, respectively. The results showed that compared with the control, maize straw treatment significantly increased the content of O-alkyl C and decreased aromatic C content, while maize straw biochar treatment showed an opposite effect. Maize straw treatment significantly increased the abundance of cbhI gene and the relative abundance of Penicillium, Gaeumannomyces and Marasmius. However, maize straw biochar treatment reduced the abundance of this gene. The relative abundance of dominant cbhI in soils was positively correlated with the content of O-alkyl C and negatively correlated with the content of aromatic C. Results of redundancy analysis showed that maize straw treatment had a significant effect on the microbial community composition of cbhI gene by changing soil O-alkyl C content, while maize straw biochar affected the microbial community composition of cbhI gene by changing soil pH, organic carbon, and aromatic C content. Maize straw biochar treatment was more effective in increasing soil organic carbon stability and reducing microbial activity associated with carbon degradation in the subtropical Moso bamboo forest ecosystem compared with maize straw treatment. Therefore, the application of biochar has positive significance for maintaining soil carbon storage in subtropical forest ecosystems.
Subject(s)
Carbon , Microbiota , Carbon/analysis , Zea mays , Soil/chemistry , Charcoal/chemistry , Poaceae , Forests , Organic ChemicalsABSTRACT
The functionalization of indoles in the carbocyclic ring has been achieved via organocatalytic enantioselective Friedel-Crafts benzhydrylation of hydroxyindoles with in situ generated ortho-quinomethanes in oil-water biphases, allowing an efficient access to varied diarylindolylmethanes with a wide substrate scope. The high yields, excellent stereoselectivities, mild conditions, low catalyst loading, and easy scalability also demonstrated the interest of this novel methodology.
ABSTRACT
A highly enantioselective homogeneous fluorination of cyclic ß-keto esters catalyzed by diphenylamine linked bis(oxazoline)-Cu(OTf)2 complexes has been established in a continuous flow microreactor. The microreactor allowed an efficient transformation with reaction times ranging from 0.5 to 20 min, and the desired products were afforded in high yields (up to 99%) with excellent enantioselectivities (up to 99% ee) at a low catalyst loading of 1 mol%.
ABSTRACT
A highly regioselective and enantioselective N-alkylation of isoxazol-5-ones with para-quinone methides promoted by bi-functional squaramide catalysts was developed. This unexpected asymmetric N-addition of isoxazolinones afforded a series of enantioenriched N-diarylmethane substituted isoxazolinones with high yields and enantioselectivities (up to 97 : 3 er). This reaction not only provides a useful approach for intermolecular chiral C-N bond formation but also demonstrates the immense potential of isoxazol-5-ones as N-nucleophiles in catalytic asymmetric reactions.
ABSTRACT
With the growing concerns on global climate change and food security, low carbon agriculture in food production attracts more attention. Low carbon agriculture needs to balance higher-level crop yields and lower greenhouse gas emission in production process. Improving nitrogen mana-gement may help mitigate greenhouse gas emission and achieve stable or higher crop yields in crop production systems. In this study, we investigated the effects of nitrogen application rates (150, 225, 300 kg N·hm-2) on the carbon footprint of spring maize-late rice rotation system in paddy field using the life cycle assessment. The results showed that greenhouse gas emission and carbon footprint increased with the nitrogen fertilizer application rates in both crops. Nitrogen fertilizer was the most important contributor to carbon footprint of spring maize ecosystem, accounting for 36.2%-50.2%. Methane emission increased with nitrogen fertilizer input and contributed the most to the carbon footprint of late rice production, accounting for 42.8%-48.0%. When the nitrogen application rate was reduced by 25% (225 kg N·hm-2) and 50% (150 kg N·hm-2), greenhouse gas emission of maize production decreased by 21.9% and 44.3%, and the carbon footprint decreased by 20.3% and 39.1%, respectively. Meanwhile, the greenhouse gas emissions of late rice decreased by 12.3% and 20.4%, and the carbon footprint of late rice decreased by 13.7% and 16.7%, respectively. The reduction of nitrogen fertilizer rate had no significant effect on maize yield, with the treatment of 225 kg N·hm-2 rate holding the highest yield in late rice ecosystem. The treatment of 150 kg N·hm-2 rate in spring maize production and 225 kg N·hm-2 rate in late rice production was the sustainable N fertilizer application rate for achieving high grain yield and reducing the carbon footprint in crop system.
Subject(s)
Agriculture/methods , Carbon Footprint , Fertilizers , Nitrogen , Oryza , Zea maysABSTRACT
A 52-day incubation experiment was conducted to investigate the effects of maize straw decomposition with combined medium element (S) and microelements (Fe and Zn) application on arable soil organic carbon sequestration. During the straw decomposition, the soil microbial biomass carbon (MBC) content and CO2-C mineralization rate increased with the addition of S, Fe and Zn, respectively. Also, the cumulative CO2-C efflux after 52-day laboratory incubation significantly increased in the treatments with S, or Fe, or Zn addition, while there was no significant reduction of soil organic carbon content in the treatments. In addition, Fe or Zn application increased the inert C pools and their proportion, and apparent balance of soil organic carbon, indicating a promoting effect of Fe or Zn addition on soil organic carbon sequestration. In contrast, S addition decreased the proportion of inert C pools and apparent balance of soil organic carbon, indicating an adverse effect of S addition on soil organic carbon sequestration. The results suggested that when nitrogen and phosphorus fertilizers were applied, inclusion of S, or Fe, or Zn in straw incorporation could promote soil organic carbon mineralization process, while organic carbon sequestration was favored by Fe or Zn addition, but not by S addition.
