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Extensive studies have been conducted on the impacts of plastic film residue on crop productivity in dryland agriculture. However, the relevant results were inconsistent or even opposite, which was most probably affected by both the size and concentration of residual films. To clarify this issue, a three-year (2019–2021) field experiment was conducted to examine plastic residue landfill effects on maize productivity using three sizes (0.4 × 0.4 cm2 (small), 4 × 4 cm2 (medium), and 10 × 10 cm2 (large)) under the low and high addition concentrations in an irrigated maize field. The data indicated that medium-sized residues significantly reduced maize yield by 7.3% and 13.8% in low and high addition levels respectively, relative to non-landfill group (CK) (p < 0.05). Large and small-sized residues under low level had no significant impact on yield (p > 0.05), while high amounts of small residues turned to positively influence yield. This trend was closely correlated with soil temperature, soil moisture, key enzyme activities, macroaggregate proportion, soil organic carbon and total nitrogen contents. Structural equation modelling and relative importance analyses demonstrated soil hydrothermal (27.4%), soil nitrogen (22.0%), and physical properties (21.1%) as primary drivers. A general trend was that the sizes of residues showed evidently greater impacts than their addition levels. Moreover, medium residues showed negative effects, while large and small ones had neutral or positive effects. For the first time, our findings confirmed the size- and concentration-dependent effects of plastic residues on crop productivity and provided a novel insight into plastic film pollution assessment & management in agricultural ecosystems. • Medium plastic residues evidently reduced maize yield across the concentrations. • Large and small plastic ones turned to neutrally and positively affect maize yield. • Soil hydrothermal and nutrient status were affected by residue size & concentration. • Residue size showed greater impacts on maize productivity than its concentration. • This study filled knowledge gap in understanding plastic residue production effect. [ABSTRACT FROM AUTHOR]

• The specific surface area of MPs is positively correlated with bacterial diversity. • The continuity between MPs and the soil interface influences bacterial diversity. • The shapes of MP dominate the assembly of soil bacterial communities. • The importance of MP concentration is not as high as expected. • Community assembly under MPs follows both stochastic and deterministic processes. Polyethylene film mulching is a key technology for soil water retention in dryland agriculture, but the aging of the films can generate a large number of microplastics with different shapes. There exists a widespread misunderstanding that the concentrations of microplastics might be the determinant affecting the diversity and assembly of soil bacterial communities, rather than their shapes. Here, we examined the variations of soil bacteria community composition and functioning under two-year field incubation by four shapes (ball, fiber, fragment and powder) of microplastics along the concentration gradients (0.01%, 0.1% and 1%). Data showed that specific surface area of microplastics was significantly positively correlated with the variations of bacterial community abundance and diversity (r=0.505, p <0.05). The fragment- and fiber-shape microplastics displayed more pronounced interfacial continuity with soil particles and induced greater soil bacterial α-diversity, relative to the powder- and ball-shape ones. Strikingly, microplastic concentrations were not significantly correlated with bacterial community indices (r=0.079, p >0.05). Based on the variations of the βNTI, bacterial community assembly actually followed both stochastic and deterministic processes, and microplastic shapes significantly modified soil biogeochemical cycle and ecological functions. Therefore, the shapes of microplastics, rather than the concentration, significantly affected soil bacterial community assembly, in association with microplastic-soil-water interfaces. [Display omitted] [ABSTRACT FROM AUTHOR]

The intercropping-led diversified tillage is crucial for sustainable development in dryland agriculture. However, the plant-plant interaction transition and its effects on soil physiochemical characteristics along soil phosphorus (P) levels are not clear. To address this issue, maize-grass pea intercropping system was used to investigate the variations in plant-plant facilitation along soil P gradients (low- to high-P) and their effects on rhizosphere soil N and P availability and microbial biomass. The data showed that total net effect (NE) was always positive, indicating facilitative effects of intercropping on total community productivity. Specifically, the relative yield (RY) for both species was greater than 0.5 in the P-deficient soils, representing mutually facilitated effects. Yet, under the P-sufficient condition, maize and grass pea acted as facilitated species and facilitator respectively. Rhizosphere phosphatase activity was significantly enhanced in the P-deficient soils, accordingly fostering P mineralization for higher P availability and N utilization. The contents of microbial biomass carbon, nitrogen and phosphorus (i.e., MBC, MBN and MBP) were evidently elevated in intercropping systems than those of monoculture. Also, global meta-analysis verified above phenomenon, showing that high P addition decreased facilitation intensity with type shift, regarding plant productivity, N and P utilization and vice versa. We confirmed a relatively full picture of P-driven facilitation intensity and type shift along stress gradients by field observation and meta-analysis. The findings provided a new insight of biodiversity in soil physiochemical traits and also revealed a critical mechanism affecting resource utilization in the P-limited soils. [Display omitted] • Plant facilitation was significantly enhanced in low soil phosphorus conditions. • Meta-analysis confirmed P availability altering interspecific facilitation model. • The universality of stress gradient hypothesis was validated in intercropping. [ABSTRACT FROM AUTHOR]

The polyethylene (PE) film mulching as a water conservation technology has been widely used in dryland agriculture, yet the long-term mulching has led to increasing accumulation of secondary pollutants in soils. The decomposition of PE film-sourced pollutants is directly associated with the enrichment of specific bacterial communities. We therefore hypothesized that plant biomass may act as an organic media to mediate the pollutant decomposition via reshaping bacterial communities. To validate this hypothesis, plant biomass (dried maize straw and living clover) was embedded at the underlying surface of PE film, to track the changes in the composition and function of bacterial communities in maize field across two years. The results indicated that both dry crop straw and alive clover massively promoted the α-diversity and abundance of dominant bacteria at plastisphere, relative to bulk soil. Bacterial communities tended to be clustered at plastisphere, forming the bacteria islands to enrich pollutant-degrading bacteria, such as Sphingobacterium , Arthrobacter and Paracoccus. As such, plastisphere bacteria islands substantially enhanced the degradation potential of chloroalkene and benzoate (p < 0.05). Simultaneously, bacterial network became stabilized and congregated at plastisphere, and markedly improved the abundance of plastisphere module hubs and connectors bacteria via stochastic process. Particularly, bacterial community composition and plastic film-sourced pollutants metabolism were evidently affected by soil pH, carbon and nitrogen sources that were mainly derived from the embedded biomass. To sum up, plant biomass embedding as a nature-based strategy (NbS) can positively mediate the decomposition of plastic-sourced pollutants through plastisphere bacteria island effects. [ABSTRACT FROM AUTHOR]