Bacteria in (vermi)composted organic wastes mostly survive when applied to an arable soil cultivated with wheat (Triticum sp. L.)

Exploring strategies for kitchen waste treatment and remediation from the perspectives of microbial ecology and genomics

Nowadays, the rapid growth of population has led to a substantial increase in kitchen waste and wasted sludge. Kitchen waste is rich in organic matter, including lignocellulose. Synergistic treatment involving kitchen waste and wasted sludge can enhance treatment process. Vermicomposting can facilitate microbial activities on organic matter. Nevertheless, the underlying mechanisms remain unclear. In this study, metagenomics was used to analyze microbial functional genes in vermicomposting. Redundancy analysis found that TOC, TN and DTN adversely affect earthworm growth and reproduction. The relative abundance of Bacteroidetes and Firmicutes increased with earthworms, thereby potentially augmenting lignocellulose degradation. The predominant functional genes included amino acid, carbohydrate, and inorganic ion conversion and metabolism. Metagenomics analysis demonstrated that GH1, GH3, GH5, GH6, GH9, GH12, GH44, GH48 and GH74, GT41, GT4, GT2, and GT51 were dominant. Furthermore, there was higher abundance of carbohydrate-active enzymes in the vermicomposting, particularly during the later phases (30-45 days). Co-occurrence network revealed that Cellvibrio in the vermicomposting exhibited a relatively dense positive correlation with other microbial groups. The findings elucidated the mechanism of vermicomposting as a promising approach for managing kitchen waste and wasted sludge.

Greenhouse gas emissions, carbon stocks and wheat productivity following biochar, compost and vermicompost amendments: comparison of non-saline and salt-affected soils

Understanding the impact of greenhouse gas (GHG) emissions and carbon stock is crucial for effective climate change assessment and agroecosystem management. However, little is known about the effects of organic amendments on GHG emissions and dynamic changes in carbon stocks in salt-affected soils. We conducted a pot experiment with four treatments including control (only fertilizers addition), biochar, vermicompost, and compost on non-saline and salt-affected soils, with the application on a carbon equivalent basis under wheat crop production. Our results revealed that the addition of vermicompost significantly increased soil organic carbon content by 18% in non-saline soil and 52% in salt-affected soil compared to the control leading to improvements in crop productivity i.e., plant dry biomass production by 57% in non-saline soil with vermicompost, while 56% with the same treatment in salt-affected soil. The grain yield was also noted 44 and 50% more with vermicompost treatment in non-saline and salt-affected soil, respectively. Chlorophyll contents were observed maximum with vermicompost in non-saline (24%), and salt-affected soils (22%) with same treatments. Photosynthetic rate (47% and 53%), stomatal conductance (60% and 12%), and relative water contents (38% and 27%) were also noted maximum with the same treatment in non-saline and salt-affected soils, respectively. However, the highest carbon dioxide emissions were observed in vermicompost- and compost-treated soils, leading to an increase in emissions of 46% in non-saline soil and 74% in salt-affected soil compared to the control. The compost treatment resulted in the highest nitrous oxide emissions, with an increase of 57% in non-saline soil and 62% in salt-affected soil compared to the control. In saline and non-saline soils treated with vermicompost, the global warming potential was recorded as 267% and 81% more than the control, respectively. All treatments, except biochar in non-saline soil, showed increased net GHG emissions due to organic amendment application. However, biochar reduced net emissions by 12% in non-saline soil. The application of organic amendments increased soil organic carbon content and crop yield in both non-saline and salt-affected soils. In conclusion, biochar is most effective among all tested organic amendments at increasing soil organic carbon content in both non-saline and salt-affected soils, which could have potential benefits for soil health and crop production.