AUTHOR=Liu Jin , Li Yang , Han Chaoqun , Yang Dongling , Yang Jianjun , Cade-Menun Barbara J. , Chen Yuanquan , Sui Peng 

TITLE=Maize-soybean intercropping facilitates chemical and microbial transformations of phosphorus fractions in a calcareous soil

JOURNAL=Frontiers in Microbiology

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2022.1028969

DOI=10.3389/fmicb.2022.1028969

ISSN=1664-302X

ABSTRACT=<p>Intercropping often substantially increases phosphorus (P) availability to plants compared with monocropping, which could be an effective strategy for soil legacy P recovery and agricultural production. However, the biogeochemical interactions among plants, microbes, and soil that mobilize P remain largely unknown in intercropping systems. Pot experiments with maize-soybean intercropping in a calcareous soil were conducted to investigate the potential chemical and biological transformation mechanisms of inorganic P (P<sub>i</sub>) and organic P (P<sub>o</sub>) using sequential extraction and Illumina MiSeq sequencing. Compared to monocropping of each crop, maize-soybean intercropping significantly enhanced total P uptake of the two crops by mobilizing Ca<sub>2</sub>-P<sub>i</sub> [extracted by bicarbonate (NaHCO<sub>3</sub>)], Al-P<sub>i</sub>/P<sub>o</sub> [extracted by ammonium fluoride (NH<sub>4</sub>F)] and Fe-P<sub>i</sub> [extracted by sodium hydroxide and sodium carbonate (NaOH-Na<sub>2</sub>CO<sub>3</sub>)] fractions. Furthermore, there were significant increases in the organic carbon content and alkaline phosphomonoesterase (ALP) and phosphodiesterase (PDE) activities as well as the abundances of <italic>Microvirga</italic>, <italic>Lysobacter</italic>, <italic>Microlunatus</italic> and <italic>Sphingomonas</italic> under maize-soybean intercropping relative to monocropping. In contrast, compared to monocroppping, no significant change in the soil pH was observed under maize-soybean intercropping. Therefore, the enhanced P uptake of the maize-soybean intercropping probably resulted from a synergistic effect of rhizosphere organic carbon deposit, increased activities of ALP and PDE, together with the bacteria (<italic>Microvirga</italic>, <italic>Lysobacter</italic>, <italic>Microlunatus</italic> and <italic>Sphingomonas</italic>) which showed correlation with soil P forms, while the generally recognized rhizosphere acidification was excluded in this investigated calcareous soil. Moreover, the selected bacterial genera exhibited a closer network in the rhizosphere of soybean compared to maize, suggesting enhanced interactions among bacteria in the soybean rhizosphere. These results provide theoretical bases for the recovery of soil legacy P by maize-soybean intercropping.</p>