减磷改变了土壤微生物群落结构和功能, 促进棉花根系生长

Reducing phosphorus alters the soil microbial community structure and function, promoting cotton root growth

  • 摘要: 土壤微生物直接参与磷素循环, 影响作物生长发育, 研究不同磷素水平下棉花根际微生物群落多样性的变化, 对活化土壤磷素和合理施肥具有重要意义。本文以连续9年磷肥定位试验为基础, 设置低磷(LP, 3.06 mg·kg−1有效磷)、中磷(MP, 19.44 mg·kg−1有效磷)、高磷(HP, 63.35 mg·kg−1有效磷) 3个磷水平处理, 研究不同磷素水平下土壤理化性质、根系形态、根际磷循环微生物多样性和关键功能基因的变化。结果表明: 土壤无机磷、有机磷和总磷含量随磷素水平增加而显著增加。与HP处理相比, LP处理的土壤有机质和全氮含量分别显著增加22.76%和35.48%, MP处理的碱解氮含量显著增加17.61%。与HP处理相比, LP处理棉花叶片、秸秆、籽棉的磷含量和P2O5携出量均显著减少, MP处理磷肥利用率显著增加。棉花0~20 cm和0~60 cm土层根长及0~20 cm土层根表面积、根冠比和比根长均随磷素水平增加而减少, 而0~20 cm土层根体积随磷素水平增加而显著增加。与HP处理相比, MP处理籽棉产量无显著差异, 而LP处理的籽棉产量显著减少7.54%。棉花根际微生物在各分类单元数量随磷素水平增加呈降低趋势; 与HP处理相比, MP处理微生物基因的Simpsom指数无显著变化, LP处理微生物基因的Simpsom指数显著增加; 在属水平上, 与HP处理相比, 除溶杆菌属(Lysobacter)、贪噬菌属(Variovorax)外, MP处理相对丰度排名前10的微生物种群排序一致; 而LP处理天山中慢生根瘤菌属(Mesorhizobium)、鞘氨醇单胞菌属(Sphingomonas)、假单胞菌属(Pseudomonas)、根瘤菌(Rhizobium)相对丰度增加, 黄色类固醇杆菌属(Steroidobacter)、慢生根瘤菌属(Bradyrhizobium)、溶杆菌属、贪噬菌属、链霉菌属(Streptomyces)、苯基杆菌属(Phenylobacterium)相对丰度减少, 其中与根系生长发育密切相关的贪噬菌属相对丰度下降52.31%。与HP处理相比, LP处理的解磷微生物芽孢杆菌属(Bacillus)、节杆菌属(Arthrobacter)相对丰度均上调, 黄杆菌属(Flavobacterium)、沙门氏菌属(Salmonella)、产碱杆菌属(Alcaligenes)和根霉菌属(Rhizopus)相对丰度均下调; MP处理的黄杆菌属相对丰度上调, 产碱杆菌属相对丰度下调。与HP处理相比, LP处理的磷养分活化过程基因丰度升高, MP处理的磷养分吸收过程基因丰度升高。因此减少施磷会增加根际土壤微生物基因多样性, 增强磷养分的活化和吸收过程, 促进根系生长, 棉花生产中可适量减少磷肥施用量, 冀中南一般棉田磷肥推荐用量(P2O5)为90 kg·hm−2

     

    Abstract: Microorganisms participate directly in the phosphorus cycle and affect crop growth and development. Studying the changes in microbial community diversity in the cotton rhizosphere under different phosphorus levels has important theoretical and practical significance for the rational application of phosphorus fertilizers. In this study, based on P2O5 application at the test field location over nine years, three phosphorus levels were established: low phosphorus (LP), medium phosphorus (MP), and high phosphorus (HP). Changes and correlation analyses of soil physical and chemical properties, cotton root morphology, rhizospheric phosphorus cycling, microbial diversity, and key functional genes were studied under different phosphorus levels. The results showed that inorganic, organic, and total phosphorus contents increased with an increase in the soil available phosphorus content. Compared with the HP treatment, the soil organic matter and total nitrogen contents significantly increased by 22.76% and 35.48% in the LP treatment, the alkaline hydrolyzed nitrogen content significantly increased by 17.61% in the MP treatment. Compared with the HP treatment, the phosphorus content and P2O5 uptake in cotton leaves, stalks, and seed cotton were significantly decreased in the LP treatment, while the phosphorus fertilizer use efficiency was significantly increased in the MP treatment. The root length and root surface area in the 0−20 cm soil layer under LP treatment were significantly increased compared with those under MP and HP treatments, while the root volume was significantly decreased compared with that under MP and HP treatments. The total root length, root-shoot ratio and specific root length in the 0−60 cm soil layer decreased significantly with the increase of phosphorus level. Compared with the HP treatment, the MP treatment showed no significant difference in seed cotton yield, whereas the LP treatment resulted in a significant 7.54% reduction in yield. With an increase in phosphorus levels, the number of rhizospheric microorganisms in each taxon decreased. Compared with HP treatment, there was no significant change in the Simpson index of microbial genes in MP treatment, while the Simpson index of microbial genes in LP treatment increased significantly. At the genus level, compared with the HP treatment, the MP treatment showed consistent ranking of the top 10 microbial taxa in relative abundance except for Lysobacter and Variovorax. In contrast, the LP treatment exhibited increased relative abundances of Mesorhizobium, Sphingomonas, Pseudomonas, and Rhizobium, while decreasing the abundances of Steroidobacter, Bradyrhizobium, Lysobacter, Variovorax, Streptomyces and Phenylobacterium. Notably, the abundance of Variovorax was significantly reduced by 52.31% in LP treatment. Compared with the HP treatment, the LP treatment showed increased relative abundances of phosphate-solubilizing microorganisms including Bacillus and Arthrobacter, while decreasing the abundances of Flavobacterium, Salmonella, Alcaligenes, and Rhizopus. In contrast, the MP treatment exhibited higher abundance of Flavobacterium but lower abundance of Alcaligenes. Compared with the HP treatment, the gene abundance of phosphorus nutrient activation process in LP treatment increased, the gene abundance of phosphorus nutrient absorption process in MP treatment increased. Therefore, reducing phosphorus application can increase the genetic diversity of rhizospheric soil microorganisms, enhance the activation and uptake of phosphorus nutrients, and promote root growth. In cotton production, the P2O5 application rate can be appropriately reduced. The recommended amount of P2O5 for cotton in Hebei Province is 90 kg·hm−2.

     

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