Preceding clover cover and liming were implemented to mitigate the adverse effects of acidic soil on choy sum (Brassica rapa var. parachinensis) production, observing significant variations in phenotypic traits under different nitrogen (N) application rates. This study investigated the dose-dependent effects of urea rates on the nutrient uptake, morphological traits, biomass and rhizosphere microbiome and metabolome profiles of choy sum, to underlying the growth variations in a winter clover-based system. A new choy sum cultivar “Yuetai No.1” was evaluated in a choy sum-maize-white clover rotation system in acidic soils in 2021 and 2022, supplied with 0 kg (N0), 25 kg (N25), 50 kg (N50), 100 kg (N100), 150 kg (N150) and 200 kg (N200) nitrogen (N)/ha. Combining 16 S rRNA sequencing and UHPLC-MS/MS metabolomics was used to evaluate the bacterial diversity and metabolic responses for N0, N100 and N200 with significantly phenotypic variations. Assessing vegetative growth revealed significant N dose-dependent growth inhibition, with N200 reducing plant height 38.8% (40.0%), root length 76.6% (45.8%), and biomass 60.9 (39.5%) in comparison to N0 in 2022 (2021), respectively. Both N100 and N200 treatments notably decreased bacteria abundance and diversity compared to N0. Notably, N200 significantly enriched Pseudomonadota, while N0 favored Gemmatimonadota, Myxococcota, and Nitrospirota. Key genera such as Bryobacter, Nitrospira, Candidatus_Solibacter, and Gemmatimonasin were more abundant in N0 soils. Co-occurrence network analysis highlighted the ecological importance of Pedosphaeraceae, Mucilaginibacter, Pedobacter, Rhodanobacter, Nitrospira, Subgroup_5, MND1 and Pseudarthrobacter. These bacterial taxa exhibited significant correlations with soil metabolites, including 1-Guanidino-1-deoxy-scyllo-inositol 4-phosphate, 5’-Butyrylphosphouridine, 1-O-(2-methoxy-4Z-hexadecenyl)-sn-glycero-3-phosphocholine, C16 Sphinganine, Palatinose, PC (17:0/0:0) and Quinoline-3-carboxamides. We conclude that N application exceeding 100 kg/ha disrupts the growth of “Yuetai No.1”, promoting a dwarf phenotype while depleting rhizosphere biodiversity and perturbing key metabolic pathways. This study underscores the critical role of soil health and root microenvironment in achieving high vegetable yields.

Winter Clover Cover Enables Reduced Nitrogen Fertilization and Sustain Choy Sum Growth and Rhizosphere Microbial-Metabolic Profiles in Acidic Soil

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发表日期：

2026年5月12日

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Si Chen,
Ningyu Li,
Zhenjiang Zhou,
Lijuan Han

摘要

Preceding clover cover and liming were implemented to mitigate the adverse effects of acidic soil on choy sum (Brassica rapa var. parachinensis) production, observing significant variations in phenotypic traits under different nitrogen (N) application rates. This study investigated the dose-dependent effects of urea rates on the nutrient uptake, morphological traits, biomass and rhizosphere microbiome and metabolome profiles of choy sum, to underlying the growth variations in a winter clover-based system. A new choy sum cultivar “Yuetai No.1” was evaluated in a choy sum-maize-white clover rotation system in acidic soils in 2021 and 2022, supplied with 0 kg (N0), 25 kg (N25), 50 kg (N50), 100 kg (N100), 150 kg (N150) and 200 kg (N200) nitrogen (N)/ha. Combining 16 S rRNA sequencing and UHPLC-MS/MS metabolomics was used to evaluate the bacterial diversity and metabolic responses for N0, N100 and N200 with significantly phenotypic variations. Assessing vegetative growth revealed significant N dose-dependent growth inhibition, with N200 reducing plant height 38.8% (40.0%), root length 76.6% (45.8%), and biomass 60.9 (39.5%) in comparison to N0 in 2022 (2021), respectively. Both N100 and N200 treatments notably decreased bacteria abundance and diversity compared to N0. Notably, N200 significantly enriched Pseudomonadota, while N0 favored Gemmatimonadota, Myxococcota, and Nitrospirota. Key genera such as Bryobacter, Nitrospira, Candidatus_Solibacter, and Gemmatimonasin were more abundant in N0 soils. Co-occurrence network analysis highlighted the ecological importance of Pedosphaeraceae, Mucilaginibacter, Pedobacter, Rhodanobacter, Nitrospira, Subgroup_5, MND1 and Pseudarthrobacter. These bacterial taxa exhibited significant correlations with soil metabolites, including 1-Guanidino-1-deoxy-scyllo-inositol 4-phosphate, 5’-Butyrylphosphouridine, 1-O-(2-methoxy-4Z-hexadecenyl)-sn-glycero-3-phosphocholine, C16 Sphinganine, Palatinose, PC (17:0/0:0) and Quinoline-3-carboxamides. We conclude that N application exceeding 100 kg/ha disrupts the growth of “Yuetai No.1”, promoting a dwarf phenotype while depleting rhizosphere biodiversity and perturbing key metabolic pathways. This study underscores the critical role of soil health and root microenvironment in achieving high vegetable yields.