Intensive monocropping of bananas decreases the soil acid buffering capacity via ammonia-oxidizing bacteria

Ammonia-oxidizing microorganisms (AOM) are vital for soil nitrogen cycling, nutrient availability, and soil health during sustainable agriculture. Long-term continuous cultivation of bananas and improper chemical fertilization affect the adaptability of AOM; however, the underlying basis for this phenomenon is unclear. This study utilized 16S rRNA gene and metagenomic sequencing techniques to examine soil from banana plantations that were continuously cultivated for 2, 3, 7, 10, 12, and 13 years (Y2, Y3, Y7, Y10, Y12, and Y13, respectively). The results indicated a significant decrease in soil acidity buffering capacity (pHBC) with increasing years of continuous cropping. Furthermore, compared with forest soil (Y0), Y7, Y10, Y12, and Y13 soils exhibited a significantly increased potential nitrification rate (PNR) as well as an abundance of ammonia-oxidizing archaea (AOA) and bacteria (AOB), with no significant difference in complete ammonia oxidizers (comammox). Principal component analysis (PCA) further demonstrated marked differences in chemical properties and ammonia-oxidizing microbial community structures between the soils under long-term (Y7, Y10, Y12, Y13) and short-term (Y2, Y3) banana cultivation. In addition, metagenome analysis results indicated that the relative abundance of Nitrososphaera-AOA and Ca. Nitrosocosmicus-AOA as well as Nitrosospira-AOB, Nitrosovibrio-AOB, Nitrosomonas-AOB, and comammox Nitrospira jacus was significantly higher in Y7 and Y13 soils than in Y0 controls. Redundancy analysis (RDA) identified pHBC, CEC, and NH₄⁺ as the primary chemical factor responsible for the differences in AOM microbial communities, whereas random forest analysis revealed that Nitrosospira-AOB significantly contributed to PNR. In summary, long-term continuous banana cultivation primarily stimulates AOB promote soil ammonia oxidation, leading to soil acidification.

Graphical Abstract