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1. Crop diversity management is widely used to increase agricultural productivity and sustainability. Recent studies have demonstrated that maize root exudates can drive interspecific facilitation to enhance N 2 fixation of bean in intercropping systems. However, the mechanisms of N 2 fixation enhancement stimulated by root exudates in the intercropping systems remain unclear.2. Four experiments were designed to provide a progressively deeper understanding of how root exudates stimulate microbial-mediated N 2 fixation. First, the effects of faba bean/maize intercropping on yields and soil microbial communities were determined in a field experiment. Second, root-derived interspecific facilitation was evaluated using a root partitioning approach. Third, the key microbial taxa in the faba bean rhizosphere were traced using 13 C-labelled maize root exudates.Fourth, the co-driven mechanism of maize root exudates and micro-organisms in the faba bean rhizosphere were explored.3. Faba bean/maize intercropping with maize residue return increased the yields of faba bean (26%), maize (27%) and broccoli (9.1%) compared to that under monocropping. Nodulin-like 4 (NODL4), chalcone-flavanone isomerase (CFI) and early nodulin-like (ENODL2) gene expression in faba bean roots intercropped with maize increased by 1.5-2.3-fold compared to that observed under monoculture.More than half of the N 2 fixation of faba bean increase under intercropping was due to interactions with micro-organisms. Nine key bacterial genera in the faba bean rhizosphere were identified by 13 C-DNA-based stable isotope probing analysis. Among them Agromyces, Arthrobacter, Bacillus, Lysobacter and Paenibacillus directly fix N 2 , while Gemmatimonas, Heliobacillus, Natronocella and Sorangium increase the N 2 fixation capacity of Azotobacter by providing additional carbon sources. These key bacteria triggered by maize root exudates played an important role in the rhizosphere facilitation of intercropping.

Arbuscular mycorrhizal fungi (AMFs) and biochar are two common alternatives to chemical fertilizers applied to soil to improve crop growth. However, their interactive effects on maize (Zea mays L.) growth, nutrient absorption, and physiological properties remain poorly understood. In this study, maize plants were grown in pots treated with biochar and AMFs Diversispora eburnea, alone or in combination. The results showed that the individual application of AMFs or biochar increased maize growth and mineral contents in shoots and roots (including P, K, Ca, Na, Mg, Fe, Mn, and Zn). The chlorophyll a, chlorophyll b, and total chlorophyll contents in AMF-treated leaves were significantly higher than those in the control treatment group. However, AMFs had no synergistic effects with biochar on maize growth, nutrient absorption, nor photosynthetic pigments. The application of biochar to the soil significantly reduced mycorrhizal colonization by 40.58% in the root tissues, accompanied by a significant decline in mycorrhizal dependency from 80.57% to −28.67%. We conclude that the application of biochar and AMFs can affect maize growth, nutrient uptake, and physiological properties. Our study can provide vital information for further resource use optimization in agroecosystems.

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A new series of uranium coordination polymers have been hydrothermally synthesized by using 1,4-naphthalene dicarboxylic acid (HNDC), namely, (HO)[(UO)(NDC)]·HO (1), (H-bpp)[(UO)(NDC)]·EtOH·5HO (2), (H-bpe)[(UO)(NDC)]·EtOH (3), (H-bpp)[(UO)(NDC)]·5HO (4), (H-bpp)[(UO)(HNDC)(NDC)]·2HO (5), and (H-bpy)[(UO)(NDC)] (6) [bpp = 1,3-di(4-pyridyl) propane, bpe = 4,4'-vinylenedipyridine, bpy = 4,4'-bipyridine]. Single-crystal X-ray diffraction demonstrates that complex 1 represents the uranyl-organic polycatenated framework derived from a simple two-dimensional honeycomb grid network structure via a HNDC linker. Complexes 2-4 contain the dinuclear motifs of the two UO pentagonal and one UO hexagonal bipyramids which are linked by NDC anions creating a (UO)(NDC) unit, and further extend to a 2D layer through NDC anions. Complex 5 displays a 1D zigzag double chain structure, in which the carboxylate groups of the NDC anions adopt a chelate mode and further extends to a 2D framework via hydrogen bonds. The 1D structure of complex 6 is similar to the zigzag chain of complex 5. In addition, powder X-ray diffraction, elemental analysis, IR, thermal stability and luminescence properties of all complexes have also been investigated in this paper. The photocatalytic properties of the six complexes for the degradation of tetracycline hydrochloride (TC) under UV irradiation have been examined. Moreover, density functional theory (DFT) calculations were carried out to explore the electronic structural and bonding properties of the uranyl complexes 1-6.