Barley genotype-specific variation in rhizodeposition derived C impacts mineralization of native soil organic matter and recent organic material

1. Barley genotype-specific variation in rhizodeposition derived C impacts
mineralization of native soil organic matter and recent organic material
inputs in soil: Evidence for redirecting crop breeding strategies towards root-trait selection
Acknowledgements
We gratefully acknowledge A Sim for his outstanding laboratory support. Special thanks
go to B Thornton, G Martin, L Brown, M Procee, Y Cook, S McIntyre and C Murphy of
the James Hutton Institute for their respective roles. This work was funded by a James
Hutton Institute international PhD studentship awarded to L Mwafulirwa.
Background
• Rhizodeposition is an important source of substrate for microbial
communities, supporting activities including soil organic matter
(SOM) and nutrient cycling
• Therefore, rhizodeposition is a potential root trait of interest for
crop plants, particularly in the context of variety selection for
sustainable production systems
• In sustainable agriculture, returns of organic materials to soil also
have a major impact on SOM/nutrient cycling and their turnover
by microbes is likely impacted by rhizodeposition
Conclusions and benefits
L. Mwafulirwa 1,2, E. Baggs 2, J. Russell 3, T. George 3, N. Morley 2, C. De La Fuente Canto 3 and E. Paterson 1
1 The James Hutton Institute, Craigiebuckler, Aberdeen, AB15 8QH, UK; 2 School of Biological Sciences, University of Aberdeen, Aberdeen, AB24 2TZ,
UK; 3 The James Hutton Institute, Invergowrie, Dundee, DD2 5DA, UK. Email: lumbani.mwafulirwa@hutton.ac.uk
Results
Methods
• 13C/15N enriched ryegrass root residues were added to soil,
following hot water extraction of the readily available C/N
from the residues
• Three barley genotypes were selected and grown under 13C
depleted CO2
• We partitioned the surface soil CO2 efflux, soil microbial
biomass C (MBC), dissolved organic-C (DOC), and amount C in
soil particle-size fractions into their component sources of
plant-, residue-, and SOM-derived C
• We also traced the flow of residue-derived N in soil solutions
and its uptake by plants
Figure 1: Potted plants (left) and a sketch of their planting system
(right) that allowed for CO2 and DOC measurements
Figure 2: Total-C respired as surface soil CO2
efflux (n=4)
Figure 3: Rates of SOM-derived CO2-C efflux
(n=4)
Figure 4: Rates of residue-derived CO2-C efflux
(n=4)
Figure 5: Total residue-derived N uptake by
barley plants at 34d (n=4)
Figure 6: Concentration of total DOC in soil
solution at 21 and 34 days after planting (n=4)
Highlights:
• Total CO2-C (Figure 2), and its
component sources of SOM- (Figure 3),
residue- (Figure 4) and plant-derived C
varied between genotypes
• There were small differences (though
not significant) in the uptake of residue-
derived N between genotypes (Figure 5)
• Where residues were added to soil, the
total DOC concentrations varied
between genotypes at 21d, 24d, and
28d, but did not vary between
genotypes at 34d (Figure 6)
• There were no significant differences in
total MBC between genotypes per
residue treatment
Objectives
• To quantify the individual and interactive effects of
rhizodeposition from barley genotypes and residue inputs to
soil on native SOM mineralization, C-stabilization and nutrient
cycling in soil
• To assess whether barley genotypes have equivalent impacts
on mineralization of recent plant-derived inputs and native
SOM
• To investigate whether genotypes that stimulate high
mineralization rates of organic soil amendments also directly
benefit through increased nutrient uptake
• The direction of SOM mineralization rates
between genotypes corresponded with
genotype impacts on ryegrass residue
mineralization in soil and plant uptake of
the residue-derived N
- potential to reduce chemical fertilizer
inputs to soil
• We demonstrated genotype differences in
impacting C-loss from soil as CO2 efflux and in
stimulating SOM mineralization
- potential for germplasm selection in barley
to control greenhouse gas emissions