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Healthy soil is essential for maintaining food security and enhancing ecosystem functions. Green manure application improves soil fertility and is an alternative to chemical fertilizers; however, research on optimizing soil health assessment systems and providing comprehensive and accurate information for local farmland green manure management models remains limited. In this study, we used maize and potato intercropped with green manure farmland in the main crop production area of a semi‐arid irrigation area in Northwest China as the research object, integrated the regional soil environment characteristics, and used principal component analysis and other methods to establish a minimum index data set including physicochemical, biological, and yield indices. A soil health assessment system applicable to the study region was constructed and optimized by drawing the scoring curve. The results showed that green manure treatment exerted a positive effect on the soil bulk density, nutrient content, extracellular enzyme activity, and the yield of maize and potato fields. This evaluation method showed that both green manure treatments could improve the soil health index of two major crop fields, with scores of 6.9 (3.7–8.6) and 6.2 (4.5–7.0) for maize and potato farmland, respectively, with a greater positive effect caused on maize. This evaluation system can not only reflect the soil conditions of farmland accurately given the application of green manure in the semi‐arid irrigation areas of northwest China but also provide reference for the promotion of organic fertilizers such as green manure and the resolution of regional soil health differences. [ABSTRACT FROM AUTHOR]

Year‐to‐year stability in crop production is a crucial aspect of feeding a growing global population. Evidence from natural ecosystems shows that increasing plant diversity generally increases the temporal stability of productivity; however, we have little knowledge of the mechanisms by which diversity affects stability. In fact, understanding the drivers of stability is a major knowledge gap in our understanding of biodiversity and ecosystem function in general. We varied resource inputs into crop monocultures and intercropping of maize/pea and maize/rapeseed for 3 years in field experiments to create a wide range of values for temporal stability, complementarity effects, selection effects, competition, and facilitation. We correlated whole‐system temporal stability in productivity with these values and the stability of competitively subordinate species and competitively dominant species in the intercrops. We then used structural equation modeling (SEM), which combines complex path models with latent variables, to estimate how interspecific interactions for water, nitrogen, and phosphorus affected the relationships between stability and these values. Intercropping treatments did not increase stability, but the wide range of stability created by our experiments allowed us to explore the relationship of many factors with stability. Complementarity correlated positively with the temporal stability of grain yield and aboveground biomass, suggesting that either facilitative interactions or niche partitioning shifted over time in ways that promoted stability. Furthermore, the temporal stability of total productivity of intercropping relied most on the stability of more productive species. However, facilitation tested by relative interaction index independently did not correlate with stability, but the temporal stability of the whole system increased as the competitive effects of competitively dominant species (pea and rapeseed) on competitively subordinate species (maize) decreased and was highest when these competitive effects were virtually zero. SEM indicated that as competition for soil nitrogen from competitively dominant species on competitively subordinate species decreased, the overall temporal stability of whole‐system aboveground biomass increased. This stability then led to greater stability in grain production. Our findings indicate that complex shifts in complementarity and competitive intensities are likely to be key mechanisms that maintain temporal stability in species‐diverse agriculture and, potentially, in natural systems. [ABSTRACT FROM AUTHOR]

Although the importance of the soil microbiome in mediating plant community structures and functions has been increasingly emphasized in ecological studies, the biological processes driving crop diversity overyielding remain unexplained in agriculture. Based on the plant–soil feedback (PSF) theory and method, we quantified to what extent and how soil microbes contributed to intercropping overyielding.Soils were collected as inocula and sequenced from a unique 10‐year field experiment, consisting of monoculture, intercropping and rotation planted with wheat (Triticum aestivum), maize (Zea mays) or faba bean (Vicia faba). A PSF greenhouse study was conducted to test microbial effects on three crops' growth in monoculture or intercropping.In wheat & faba bean (W&F) and maize & faba bean (M&F) systems, soil microbes drove intercropping overyielding compared to monoculture, with 28%–51% of the overyielding contributed by microbial legacies. The overyielding effects resulted from negative PSFs in both systems, as crops, in particular faba bean grew better in soils conditioned by other crops than itself. Moreover, faba bean grew better in soils from intercropping or rotation than from the average of monocultures, indicating a strong positive legacy effect of multispecies cropping systems. However, with positive PSF and negative legacy benefit effect of intercropping/rotation, we did not observe significant overyielding in the W&M system.With more bacterial and fungal dissimilarities by metabarcoding in heterospecific than its own soil, the better it improved faba bean growth. More detailed analysis showed faba bean monoculture soil accumulated more putative pathogens with higher Fusarium relative abundance and more Fusarium oxysporum gene copies by qPCR, while in heterospecific soils, there were less pathogenic effects when cereals were engaged. Further analysis in maize/faba bean intercropping also showed an increase of rhizobia relative abundance.Synthesis and applications. Our results demonstrate a soil microbiome‐mediated advantage in intercropping through suppression of the negative PSF of pathogens and increasing beneficial microbes. As microbial mediation of overyielding is context‐dependent, we conclude that the dynamics of both beneficial and pathogenic microbes should be considered in designing cropping systems for sustainable agriculture, particularly including combinations of legumes and cereals. [ABSTRACT FROM AUTHOR]