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<p>The impacts of conservation tillage on photosynthetic carbon (C) allocation to crop components and soil microbial assimilation remain poorly understood. This study quantified photosynthetic C allocation, rhizosphere C flux, and microbial utilization in rhizosphere and bulk soils using in-site <sup>13</sup>C isotope labelling in fields managed for 15-years under no-tillage (NTS), conventional plow tillage (CTS), and rotary tillage (RTS). Compared with CTS and RTS, NTS significantly increased photosynthetic C fixation during wheat flowering by 60% and 57%, respectively, and during maize tasseling by 57% and 69%, respectively. Photosynthetic C allocation to the rhizosphere in NTS were 170.0% and 46.3% higher during wheat flowering and maize V8 (1&#xa0;day after labelling) compared to CTS, respectively. This improved assimilative efficiency under NTS created synergies between crop growth and rhizosphere C allocation. Moreover, NTS enhanced the capacity of arbuscular mycorrhizal fungi (AMF) to acquire rhizosphere assimilates, while decreasing that of gram-positive bacteria (G+). Positive correlations between <sup>13</sup>C and total <sup>13</sup>C-phospholipid fatty acid (PLFA) in bulk soil during the wheat season and rhizosphere soil during the maize season suggested that microbial utilization of assimilates contributed to SOC sequestration. In addition, <sup>13</sup>C-CO<sub>2</sub> loss was positively correlated with the fungi to bacteria ratio of <sup>13</sup>C-PLFA, underscoring the role of fungal assimilation in C cycling. Overall, conservation tillage improved rhizosphere C allocation efficiency and AMF assimilation capacity, thereby facilitating enhanced sequestration of rhizosphere organic matter.</p>

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A 13C-PLFA approach to assess the crop carbon allocation efficiency and arbuscular mycorrhizal assimilation capacity under conservation tillage

  • 期刊论文

  • 发表日期：

    2025年10月11日

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  • Wen-Sheng Liu,
  • Shuo Yao,
  • Zhuo-Jun Lin,
  • Olatunde Pelumi Oladele,
  • Yash Pal Dang,
  • Xin Zhao,
  • Hai-Lin Zhang

摘要

The impacts of conservation tillage on photosynthetic carbon (C) allocation to crop components and soil microbial assimilation remain poorly understood. This study quantified photosynthetic C allocation, rhizosphere C flux, and microbial utilization in rhizosphere and bulk soils using in-site 13C isotope labelling in fields managed for 15-years under no-tillage (NTS), conventional plow tillage (CTS), and rotary tillage (RTS). Compared with CTS and RTS, NTS significantly increased photosynthetic C fixation during wheat flowering by 60% and 57%, respectively, and during maize tasseling by 57% and 69%, respectively. Photosynthetic C allocation to the rhizosphere in NTS were 170.0% and 46.3% higher during wheat flowering and maize V8 (1 day after labelling) compared to CTS, respectively. This improved assimilative efficiency under NTS created synergies between crop growth and rhizosphere C allocation. Moreover, NTS enhanced the capacity of arbuscular mycorrhizal fungi (AMF) to acquire rhizosphere assimilates, while decreasing that of gram-positive bacteria (G+). Positive correlations between 13C and total 13C-phospholipid fatty acid (PLFA) in bulk soil during the wheat season and rhizosphere soil during the maize season suggested that microbial utilization of assimilates contributed to SOC sequestration. In addition, 13C-CO2 loss was positively correlated with the fungi to bacteria ratio of 13C-PLFA, underscoring the role of fungal assimilation in C cycling. Overall, conservation tillage improved rhizosphere C allocation efficiency and AMF assimilation capacity, thereby facilitating enhanced sequestration of rhizosphere organic matter.