TY - JOUR

T1 - Maize rhizosphere priming: field estimates using 13C natural abundance

AU - Kumar, Amit

AU - Kuzyakov, Yakov

AU - Pausch, Johanna

PY - 2016/12/1

Y1 - 2016/12/1

N2 - Introduction: Root-mediated changes in soil organic matter (SOM) decomposition, termed rhizosphere priming effects (RPE), play crucial roles in the global carbon (C) cycle, but their mechanisms and field relevance remain ambiguous. We hypothesize that nitrogen (N) shortages may intensify SOM decomposition in the rhizosphere because of increase of fine roots and rhizodeposition. Methods: RPE and their dependence on N-fertilization were studied using a C 3-to-C 4 vegetation change. N-fertilized and unfertilized soil cores, with and without maize, were incubated in the field for 50 days. Soil CO 2 efflux was measured, partitioned for SOM- and root-derived CO 2, and RPE was calculated. Plant biomass, microbial biomass C (MBC) and N (MBN), and enzyme activities (β-1,4-glucosidase; N-acetylglucosaminidase; L-leucine aminopeptidase) were analyzed. Results: Roots enhanced SOM mineralization by 35 % and 126 % with and without N, respectively. This was accompanied by higher specific root-derived CO 2 in unfertilized soils. MBC, MBN and enzyme activities increased in planted soils, indicating microbial activation, causing positive RPE. N-fertilization had minor effects on MBC and MBN, but it reduced β-1,4-glucosidase and L-leucine aminopeptidase activities under maize through lower root-exudation. In contrast, N-acetylglucosaminidase activity increased with N-fertilization in planted and unplanted soils. Conclusions: This study showed the field relevance of RPE and confirmed that, despite higher root biomass, N availability reduces RPE by lowering root and microbial activity.

AB - Introduction: Root-mediated changes in soil organic matter (SOM) decomposition, termed rhizosphere priming effects (RPE), play crucial roles in the global carbon (C) cycle, but their mechanisms and field relevance remain ambiguous. We hypothesize that nitrogen (N) shortages may intensify SOM decomposition in the rhizosphere because of increase of fine roots and rhizodeposition. Methods: RPE and their dependence on N-fertilization were studied using a C 3-to-C 4 vegetation change. N-fertilized and unfertilized soil cores, with and without maize, were incubated in the field for 50 days. Soil CO 2 efflux was measured, partitioned for SOM- and root-derived CO 2, and RPE was calculated. Plant biomass, microbial biomass C (MBC) and N (MBN), and enzyme activities (β-1,4-glucosidase; N-acetylglucosaminidase; L-leucine aminopeptidase) were analyzed. Results: Roots enhanced SOM mineralization by 35 % and 126 % with and without N, respectively. This was accompanied by higher specific root-derived CO 2 in unfertilized soils. MBC, MBN and enzyme activities increased in planted soils, indicating microbial activation, causing positive RPE. N-fertilization had minor effects on MBC and MBN, but it reduced β-1,4-glucosidase and L-leucine aminopeptidase activities under maize through lower root-exudation. In contrast, N-acetylglucosaminidase activity increased with N-fertilization in planted and unplanted soils. Conclusions: This study showed the field relevance of RPE and confirmed that, despite higher root biomass, N availability reduces RPE by lowering root and microbial activity.

KW - C3/C4vegetation change

KW - Enzyme activities

KW - Microbial biomass

KW - N-fertilization

KW - SOM decomposition

KW - Soil CO2

KW - Ecosystems Research

UR - http://www.scopus.com/inward/record.url?scp=84974827666&partnerID=8YFLogxK

U2 - 10.1007/s11104-016-2958-2

DO - 10.1007/s11104-016-2958-2

M3 - Journal articles

VL - 409

SP - 87

EP - 97

JO - Plant and Soil

JF - Plant and Soil

SN - 0032-079X

IS - 1-2

ER -