Cultivating ecological benefits in agricultural systems through greenhouse gas emission reduction will offer extra economic benefits for farmers. The reported studies confirmed that organic fertilizer application could promote soil carbon sequestration and mitigate greenhouse gas emissions under suitable tillage practices in a short period of time. Here, a field experiment was conducted using a two-factor randomized block design (organic fertilizers and tillage practices) with five treatments. The results showed that the application of microbial fertilizers conserved soil heat and moisture, thereby significantly reducing CO₂ emissions (6.9–18.9%) and those of N₂O and CH₄ fluxes during corn seasons, compared with chemical fertilizer application. Although deep tillage increased total CO₂ emissions by 4.9–37.7%, it had no significant effect on N₂O and CH₄ emissions. Application of microbial organic fertilizer increased corn yield by 21.5%, but it had little effect on the yield of wheat. Overall, application of microbial fertilizers significantly reduced soil GHG emission and concurrently increased yield under various tillage practices in a short space of time. With this, it was critical that microbial fertilizer be carefully studied for application in wheat–corn cropping systems.

Soil inorganic carbon (SIC) represents the main soil carbon pool in drylands with a high geologic residence time for carbon sequestration. Recent studies have shown that SIC is not stable as previously supposed, and can be employed by certain microbes and transformed into organics in soils; however, this transformation remains largely unexplored. We performed in situ ¹³C tracing in desert bulk soil and employed metagenomics to predict the microbial metabolic processes associated with carbon transformation. The tracing data showed that the ¹³C signature profile in soil organic carbon (SOC) originated from SIC with a carbon transformation content of 6.881 mg m⁻² during the feeding periods, corresponding to a rate of 3.276 μg kg⁻¹ d⁻¹. Metagenomic analysis identified genes encoding enzymes related to microbial CO₂ and fixation, accounting for 0.448% (based on Kyoto Encyclopedia of Genes and Genomes database) and 0.668% (based on Evolutionary genealogy of genes: Non‐supervised Orthologous Groups database) of all ascertained genes. Soil microbes, from a broad taxonomic range, harboring these genes mainly contributed toward chemoautotrophic and heterotrophic carbon fixation. Our results demonstrated that the microbes employed the chemoautotrophic and heterotrophic pathways, namely, dark microbial pathways, for SIC transformation into SOC. Although the amount of SOC derived from the dark microbial fixation process was not assessed, the present study highlights a neglected carbon transformation process mediated by soil microbes in drylands and provides insights into carbon transformation of SIC to SOC in dryland soil.

Agricultural straw waste and livestock manure are often misplaced resources. The separation of planting and breeding has induced significant pressure on the environment. Thus, there is a growing need for a system that can integrate crop and livestock farming to improve resource efficiency. To clarify the current state of crop–livestock systems in China and elsewhere, a bibliometric analysis was conducted for a total of 18,628 published English and 3460 published Chinese research articles and dissertations on circular agriculture. The published research papers were taken from the ISI Web of Science and CNKI database to explore research hotpots, research methods, theme trends, and mainstream technical models of crop–livestock systems from 1981 to 2021. Recent progress in crop–livestock systems was analyzed from ecological, economic, social benefits, and stakeholder perspectives. The research results showed that compared with traditional agricultural models, crop–livestock systems had far more ecologic and social benefits, including gaining higher net income and input-output ratio, improving soil quality, and mitigating global warming. The drivers of crop–livestock systems’ development were also analyzed from stakeholders’ perspectives. The study provides insights into the development of circular agriculture by reducing the pollution risks of agricultural waste and improving both ecological and economic benefits of the system.

The formation of soil inorganic carbon in saline–alkali lands is of great significance for enhancing soil carbon sequestration. As for the formation mechanisms, in addition to the discovered abiotic mechanisms, the microbial mechanisms remain unclear. To address this, soil microbes were isolated from the saline–alkali farmland of the Yellow River Delta in north China. Then, their capacity for carbonate precipitation formation was determined. Ten microbial strains were obtained from the soil. Of these, seven strains (four bacterial strains and three fungal strains), belonging to Rhodococcus sp., Pseudomonas sp., Bacillus sp., Streptomyces sp., Aspergillus sp., Cladosporium sp., and Trichoderma sp., formed carbonate precipitates in the range of 89.77~383.37 mg. Moreover, the formation of carbonate precipitates was related to specific metabolisms by which microbes can raise the pH (from 7.20 to >8.00), suggesting that soil microbes that can enhance pH values by specific metabolisms containing the function of carbonate formation. Although an in situ experiment is needed to confirm such capacity, these results showed that soil bacteria and fungi existing in the saline–alkali farmland soil can form carbonate precipitates. The present study provided a microbial perspective for the mechanism of soil inorganic carbon formation, further implying a microbial potential of soil carbon sequestration in saline–alkali farmlands.