Rhizosphere priming promotes plant nitrogen acquisition by microbial necromass recycling

• Published in: Plant, cell and environment Vol. 47; no. 6; pp. 1987 - 1996
• Main Authors: Pausch, Johanna, Holz, Maire, Zhu, Biao, Cheng, Weixin
• Format: Journal Article
• Language: English
• Published: United States Wiley Subscription Services, Inc 01.06.2024
• Subjects: 13CO2 continuous labelling; 15N natural abundance; Carbon - metabolism; crops; Decomposition; Design of experiments; Experimental design; Exudates; Exudation; Labeling; legumes; Microorganisms; Nitrogen; Nitrogen - metabolism; Nitrogen Isotopes; Organic matter; Organic soils; plant nutrition; Plant Roots - metabolism; Plant Roots - microbiology; Plant Shoots - metabolism; Plant Shoots - microbiology; Plant species; Plants - metabolism; Plants - microbiology; Priming; Recycling; Rhizosphere; Rhizosphere microorganisms; Soil - chemistry; Soil horizons; Soil Microbiology; Soil microorganisms; Soil organic matter; soil respiration; Soil types; Soils; Subsoils; Topsoil; plant nutrition; legumes; soil respiration; 13CO2 continuous labelling; crops; 15N natural abundance
• ISSN: 0140-7791; 1365-3040
• DOI: 10.1111/pce.14858

Nitrogen availability in the rhizosphere relies on root‐microorganism interactions, where root exudates trigger soil organic matter (SOM) decomposition through the rhizosphere priming effect (RPE). Though microbial necromass contribute significantly to organically bound soil nitrogen (N), the role of RPEs in regulating necromass recycling and plant nitrogen acquisition has received limited attention. We used 15N natural abundance as a proxy for necromass‐N since necromass is enriched in 15N compared to other soil‐N forms. We combined studies using the same experimental design for continuous 13CO2 labelling of various plant species and the same soil type, but considering top‐ and subsoil. RPE were quantified as difference in SOM‐decomposition between planted and unplanted soils. Results showed higher plant N uptake as RPEs increased. The positive relationship between 15N‐enrichment of shoots and roots and RPEs indicated an enhanced necromass‐N turnover by RPE. Moreover, our data revealed that RPEs were saturated with increasing carbon (C) input via rhizodeposition in topsoil. In subsoil, RPEs increased linearly within a small range of C input indicating a strong effect of root‐released C on decomposition rates in deeper soil horizons. Overall, this study confirmed the functional importance of rhizosphere C input for plant N acquisition through enhanced necromass turnover by RPEs. Summary statement Interactions between roots and microorganisms in the rhizosphere enhance nitrogen availability through the rhizosphere priming effect (RPE). Our study confirmed that increasing RPEs promote higher plant nitrogen uptake and indicate enhanced turnover of necromass‐nitrogen through rhizosphere priming.