Mitigating microplastic stress on peanuts: The role of biochar-based synthetic community in the preservation of soil physicochemical properties and microbial diversity.

Tire-derived rubber crumbs (RC), as a new type of microplastics (MPs), harms both the environment and human health. Excessive use of plastic, the decomposition of which generates microplastic particles, in current agricultural practices poses a significant threat to the sustainability of agricultural ecosystems, worldwide food security and human health. In this study, the application of biochar, a carbon-rich material, to soil was explored, especially in the evaluation of synthetic biochar-based community (SynCom) to alleviate RC-MP-induced stress on plant growth and soil physicochemical properties and soil microbial communities in peanuts. The results revealed that RC-MPs significantly reduced peanut shoot dry weight, root vigor, nodule quantity, plant enzyme activity, soil urease and dehydrogenase activity, as well as soil available potassium, and bacterial abundance. Moreover, the study led to the identification highly effective plant growth-promoting rhizobacteria (PGPR) from the peanut rhizosphere, which were then integrated into a SynCom and immobilized within biochar. Application of biochar-based SynCom in RC-MPs contaminated soil significantly increased peanut biomass, root vigor, nodule number, and antioxidant enzyme activity, alongside enhancing soil enzyme activity and rhizosphere bacterial abundance. Interestingly, under high-dose RC-MPs treatment, the relative abundance of rhizosphere bacteria decreased significantly, but their diversity increased significantly and exhibited distinct clustering phenomenon. In summary, the investigated biochar-based SynCom proved to be a potential soil amendment to mitigate the deleterious effects of RC-MPs on peanuts and preserve soil microbial functionality. This presents a promising solution to the challenges posed by contaminated soil, offering new avenues for remediation.

The impact of arbuscular mycorrhizal fungi and endophytic bacteria on peanuts under the combined pollution of cadmium and microplastics.

It remains unclear how symbiotic microbes impact the growth of peanuts when they are exposed to the pollutants cadmium (Cd) and microplastics (MPs) simultaneously. This study aimed to investigate the effects of endophytic bacteria Bacillus velezens SC60 and arbuscular mycorrhizal fungus Rhizophagus irregularis on peanut growth and rhizosphere microbial communities in the presence of Cd at 40 (Cd40) or 80 (Cd80) mg kg-1 combined without MP or the presence of low-density polyethylene (LDPE) and poly butyleneadipate-co-terephthalate (PBAT). This study assessed soil indicators, plant parameters, and Cd accumulation indicators. Results showed that the application of R. irregularis and B. velezens significantly enhanced soil organic carbon and increased Cd content under the conditions of Cd80 and MPs co-pollution. R. irregularis and B. velezens treatment increased peanut absorption and the enrichment coefficient for Cd, with predominate concentrations localized in the peanut roots, especially under combined pollution by Cd and MPs. Under treatments with Cd40 and Cd80 combined with PBAT pollution, soil microbes Proteobacteria exhibited a higher relative abundance, while Actinobacteria showed a higher relative abundance under treatments with Cd40 and Cd80 combined with LDPE pollution. In conclusion, under the combined pollution conditions of MPs and Cd, the co-treatment of R. irregularis and B. velezens effectively immobilized Cd in peanut roots, impeding its translocation to the shoot.

Plastic footprint deteriorates dryland carbon footprint across soil-plant-atmosphere continuum.

Plastic fragments are widely found in the soil profile of terrestrial ecosystems, forming plastic footprint and posing increasing threat to soil functionality and carbon (C) footprint. It is unclear how plastic footprint affects C cycling, and in particularly permanent C sequestration. Integrated field observations (including 13C labelling) were made using polyethylene and polylactic acid plastic fragments (low-, medium- and high-concentrations as intensifying footprint) landfilling in soil, to track C flow along soil-plant-atmosphere continuum (SPAC). The result indicated that increased plastic fragments substantially reduced photosynthetic C assimilation (p < 0.05), regardless of fragment degradability. Besides reducing C sink strength, relative intensity of C emission increased significantly, displaying elevated C source. Moreover, root C fixation declined significantly from 21.95 to 19.2 mg m-2, and simultaneously root length density, root weight density, specific root length and root diameter and surface area were clearly reduced. Similar trends were observed in the two types of plastic fragments (p > 0.05). Particularly, soil aggregate stability was significantly lowered as affected by plastic fragments, which accelerated the decomposition rate of newly sequestered C (p < 0.05). More importantly, net C rhizodeposition declined averagely from 39.77 to 29.41 mg m-2, which directly led to significant decline of permanent C sequestration in soil. Therefore, increasing plastic footprint considerably worsened C footprint regardless of polythene and biodegradable fragments. The findings unveiled the serious effects of plastic residues on permanent C sequestration across SPAC, implying that current C assessment methods clearly overlook plastic footprint and their global impact effects.

Plastic mulching reduces nitrogen footprint of food crops in China: A meta-analysis.

Sustainably feeding the growing population amid rising global temperatures and dwindling resources is a grand challenge facing mankind. Plastic mulching (PM) is widely used in China aiming to the increase of crop productivity. However, the impact of PM on reactive nitrogen (Nr) emissions and nitrogen (N) footprint has not been explicitly described. In this study, we collected 4051 observations from 394 published papers for potato (Solanum tuberosum L.), maize (Zea mays L.), and wheat (Triticum aestivum L.), and used meta-analysis to investigate how PM affected crop yield, net economic return, Nr emissions, and N footprints including nitrogen footprint per unit of output energy (NFo) and nitrogen footprint per unit of net economic return (NFe) at regional scale and across a range of precipitation and N fertilization gradients in China. The meta-analysis showed that compared to non-PM practice, PM increased grain yield by 25, 27, and 20% in potato, maize, and wheat, respectively, and enhanced net economic return by 19, 29, and 22%, respectively, with corresponding reduction in NFo of 24, 36, and 18% and NFe of 19, 37, and 19%, respectively. Potato and maize had greater energy output and net economic return than wheat. Plastic mulching was more effective in improving net economic return (or energy output) and reducing N footprints (i.e., NFe and NFo) in the semiarid region (i.e., annual precipitation <600 mm) when N was applied at 100-200 kg N ha-1, especially in potato and maize. Our analysis suggests that the use of PM enhanced grain yield and net economic return while lowering the N footprint without increasing Nr emission. Therefore, PM has great potential to mitigate Nr loss in China when crop species, N fertilization rate, and local environmental factors (i.e., growing region and annual precipitation) are appropriately considered.