AUTHOR=Lu Jiayu , Yang Jinfeng , Keitel Claudia , Yin Liming , Wang Peng , Cheng Weixin , Dijkstra Feike A. 

TITLE=Belowground Carbon Efficiency for Nitrogen and Phosphorus Acquisition Varies Between Lolium perenne and Trifolium repens and Depends on Phosphorus Fertilization

JOURNAL=Frontiers in Plant Science

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2022.927435

DOI=10.3389/fpls.2022.927435

ISSN=1664-462X

ABSTRACT=<p>Photosynthetically derived carbon (C) is allocated belowground, allowing plants to obtain nutrients. However, less is known about the amount of nutrients acquired relative to the C allocated belowground, which is referred to as C efficiency for nutrient acquisition (CENA). Here, we examined how C efficiency for nitrogen (N) and phosphorus (P) acquisition varied between ryegrass (<italic>Lolium perenne</italic>) and clover (<italic>Trifolium repens</italic>) with and without P fertilization. A continuous <sup>13</sup>C-labeling method was applied to track belowground C allocation. Both species allocated nearly half of belowground C to rhizosphere respiration (49%), followed by root biomass (37%), and rhizodeposition (14%). With regard to N and P, CENA was higher for clover than for ryegrass, which remained higher after accounting for relatively low C costs associated with biological N<sub>2</sub> fixation. Phosphorus fertilization increased the C efficiency for P acquisition but decreased the C efficiency for N acquisition. A higher CENA for N and P in clover may be attributed to the greater rhizosphere priming on soil organic matter decomposition. Increased P availability with P fertilization could induce lower C allocation for P uptake but exacerbate soil N limitation, thereby making N uptake less C efficient. Overall, our study revealed that species-specific belowground C allocation and nutrient uptake efficiency depend on which nutrient is limited.</p>