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Plant–plant competitive and facilitative interactions might strongly affect the biodiversity effect and field productivity of intercropping system under the condition of limited resources such as available phosphorus (P). To test this hypothesis, the maize–grass pea intercropping system with five P application gradients (from low- to high-P) was experimentally investigated and the global meta-analysis validation was simultaneously performed. The main objectives of this study included as: 1) to examine the characteristics of plant–plant interaction variations along soil P addition gradients; 2) to identify the shift from interspecific complementarity to selection effect regarding the productivity and nutrient uptake and its driving mechanism; 3) to verify the universality of above phenomenon via global meta-analysis and explore the general pattern of P-dependent plant–plant interactions in the intercropping systems. Regardless of growing seasons, the total net effect of intercropping system was always >0, showing net facilitative effects of plant–plant interactions on field productivity and nutrient uptake efficiency, relative to monoculture systems. On average, the yield, biomass, N and P uptake were elevated by 3.0–13.7%, 3.2–12.8%, 7.5–20.1% and 5.6–18.9% in intercropping respectively, relative to those of monoculture. On the other hand, the contribution of complementarity effect to the total net effect was up to 78.7%, much more than that of selection effect (21.3%). The relative interaction index tended to decline remarkably with increasing soil P availability (from 0.097–0.126 to 0.027–0.029), suggesting that the facilitation (rather than the competition) dominated in intercropping under the low-P condition. Furthermore, the intercropped grass pea decreased the harvest index and allocated more biomass to vegetative growth as a result of the enhanced interspecific competition under the P-sufficient condition. Finally, the meta-analysis demonstrated that intercropping system had greater relative benefits regarding field productivity and N/P acquisition and utilization than monoculture system. In the meanwhile, the intensity of interspecific facilitative effect was enhanced under the P-deficient condition. Field observations presented the evidences regarding the P-dependent plant-plant interactions and its effects on field productivity in the maize-grass pea intercropping system. The meta-analysis confirmed that high P application decreased the interspecific facilitative effects in terms of field productivity and nutrient utilization in the intercropping systems. But the low-P condition led to the opposite trend, i.e. facilitative effect dominated in the intercropping for greater productivity efficiency. Graphical abstract elucidates the plant-plant interaction pattern in maize-grass pea intercropping system according to field observation and meta-analysis [Display omitted] • Effect of interspecific competition & facilitation on field productivity along soil P gradients in intercropping system is unclear • To examine how the plant–plant interactions affected crop productivity and nutrient uptake via field observations & meta-analyses • Intercropping led to greater net effects on productivity and N/P uptake efficiency via facilitative interactions than monoculture • Complementarity effect was dominant to ensure productivity benefit in low-P soil, yet competitive effect dominated in high-P soil • P-dependent plant-plant interaction efficiently mediated relative field productivity and resource benefits in intercropping system. [ABSTRACT FROM AUTHOR]

Background and Aims: Selection effect (SE) and complementarity effect (CE) are often considered as two key indicators to mediate the positive diversity-productivity relationship in the maize-legume intercropping system, as intercropping generally enables crops to use the available resources more efficiently than monoculture. Yet, it is unclear whether soil moisture drives the SE and CE transformation, plant-plant interaction, and accordingly affect the productivity. Methods: A two-year field experiment was conducted to explore the impacts of soil water status (with and without plastic mulching) on interspecific interaction and productivity and its key mechanism in the maize-faba bean intercropping system. Results: Low soil moisture reduced the net effect (NE) and land equivalent ratio (LER) with evident yield loss (NE < 0 and LER = 1.05), whereas the improved soil moisture reversed this trend and resulted in overyielding (NE > 0 and LER = 1.13). Regardless of soil moisture, faba bean was the dominant species and maize was the inferior one. Low soil moisture promoted the contribution of SE to productivity (P < 0.05). In contrast, high moisture turned to lower the competition intensity of faba bean against maize and accordingly promote the transformation of biodiversity effect from SE to CE. The main mechanism was that the water competition imposed by faba bean strips on maize ones decreased the NE through reducing photosynthetic rate and water use efficiency of maize. Conclusion: The adaptive transitions of interspecific relationship and the biodiversity effect were driven by soil water availability. This novel phenomenon should be emphasized in the crop diversity management of intercropping system in the rainfed region. [ABSTRACT FROM AUTHOR]

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]

Plastic film residuals are increasingly remaining in cultivated lands. However, it is a critical issue how residual plastic type and thickness affect soil properties and crop yield. To address this issue, in situ landfill was conducted using thick polyethylene (PEt1), thin polyethylene (PEt2), thick biodegradable (BIOt1), thin biodegradable (BIOt2) residues, and CK (control) with no residues landfill in a semiarid maize field. The findings demonstrated that the impact of various treatments on soil characteristics and maize yield varied considerably. Soil water content decreased by 24.82% in PEt1 and 25.43% in PEt2, compared to BIOt1 and BIOt2, respectively. BIOt2 treatment increased soil bulk density by 1.31 g cm−3 and lowered soil porosity by 51.11%, respectively; it also elevated the silt/clay proportion by 49.42% relative to CK. In contrast, microaggregate composition in PEt2 was higher (43.02%). Moreover, BIOt2 lowered soil nitrate (NO 3 −) and ammonium (NH 4 +) content. Compared with other treatments, BIOt2 resulted in significantly higher soil total nitrogen (STN) and lower SOC/STN. Finally, BIOt2 exhibited the lowest water use efficiency (WUE) (20.57 kg ha−1 mm−1) and yield (6896 kg ha−1) among all the treatments. Therefore, BIO film residues exhibited detrimental impacts on soil quality and maize productivity compared to PE film ones. Considering film thickness, thin residual films more evidently influenced soil quality and maize productivity than thick film ones. [Display omitted] • BIO enhanced soil bulk density and lowered porosity, while thick PE residues didn't. • BIO significantly reduced SOC/STN, but thick PE residues exhibited a minor effect. • Relative to thick PE and CK, BIO residue lowered soil inorganic nitrogen. • WUE and yield decreased under BIO residues, while thick PE ones had a slight effect. • Thick PE and thin BIO residues had the least and most harmful impact, respectively. [ABSTRACT FROM AUTHOR]