Effects of Carbon Sequestration Methods on Soil Respiration and Root Systems in Microcosm Experiments and In Vitro Studies

Antonio Gelsomino, Maria Rosaria Panuccio, Agostino Sorgona, Maria Rosa Abenavoli, and Maurizio Badiani

Abstract In the framework of an interdisciplinary research devoted at increasing soil capacity to act as carbon sink by means of innovative and sustainable strategies (the MESCOSAGR Project), we studied, in microcosm-scale model systems, changes of selected soil chemical properties, soil CO2 efflux, and root morpho-topology after addition of either mature compost or a biomimetic catalyst (CAT) (synthetic water-soluble iron-porphyrin), as single addition or in combination of the two treatments. Direct effects of CAT on seed germination, seedling establishment, and plant growth were also evaluated in model plant species. When applied to bare soil, CAT was able to reduce CO2 emission from soil. Soil amendment of compost alone stimulated CO2 emission from soil, whereas its combined addition with CAT strongly depressed the compost-induced CO2 release. In planted microcosms, the contribution of the rhizosphere-derived CO2 efflux markedly increased the total soil respiration and CAT addition further stimulated CO2 release from soil. It is thus suggested that iron-porphyrin, growth of maize root, and CO2 release are functionally interconnected. The increased total soil respiration observed in planted systems may be due to a larger contribution of the rhizosphere-derived CO2 efflux, as a consequence of secondary actions or specific mutual interactions of the catalyst-root system. The direct CAT effect on model plant species implied a complex pattern of dose-dependent, and, remarkably, species-specific responses, as observed in both root systems and aerial plant parts. The observed strong CAT promotion of the synthesis of photosynthetic pigments might indicate an in planta uptake and translocation of the CAT molecule, prompting to envisage potential applications of this molecule in a wider agro-biotechnological context.

A. Gelsomino (*) • M.R. Panuccio • A. Sorgona • M.R. Abenavoli • M. Badiani Dipartimento BIOMAA, Universita Mediterranea, Salita Melissari, 89124 Reggio Calabria, Italy e-mail: [email protected]

A. Piccolo (ed.), Carbon Sequestration in Agricultural Soils,

DOI 10.1007/978-3-642-23385-2_10, © Springer-Verlag Berlin Heidelberg 2012

Abbreviations

CAT

[meso-tetra(2,6-dichloro-3-sulfonatophenyl) porphyrinate of Fe(III)

chloride]

CEC

Cation exchange capacity

Chl

Chlorophyll

Chlide

Chlorophyllide

EC

Electrical conductivity

F

Root fineness

LR

Root length

MS

Murashige and Skoog medium

Pchlide

Protochlorophyllide

POR

NADPH:protochlorophyllide oxidoreductase

RMR

Root mass ratio

SOM

Soil organic matter

TD

Tissue mass density

TI

Topological index

TN

Total nitrogen

TOC

Total organic carbon

VR

Root volume

WP

Plant dry weight

WR

Root dry weight

WS

Shoot dry weight

10.1 Introduction

Enhancing CO2 sequestration in soil - that is, the transfer of atmospheric CO2 into a persistent terrestrial pool - can be considered an efficient strategy for balancing the atmospheric CO2 enrichment due to anthropogenic emissions, which is one of the main factors contributing to global climate change (Lal 2007).

Recent new insights into the soil organic carbon cycle suggest that some sustainable management practices, such as (1) protecting easily biodegradable organic fraction by means of humified and hydrophobic organic compounds, such as compost from agricultural by-products (Piccolo and Teshale 1998), and (2) oxidative polymerization of soil organic matter (SOM) by catalysis, or biomimetic photosensitization in the presence of solar radiation (Piccolo et al. 2011), appears to be particularly promising to increase carbon sequestration by agricultural soils and reduce greenhouse gas emissions.

In such context, Piccolo et al. (2005) and Smejkalova and Piccolo (2005) have been recently proposing the use of a synthetic, water-soluble iron-porphyrin [meso-tetra(2,6-dichloro-3-sulfonatophenyl) porphyrinate of Fe(III)chloride] as a chemical catalyst (CAT, in the following) capable to mimic the action of soil microbial enzymes involved in the oxidative polymerization of natural precursor of humic molecules (see Chap. 1).

The MESCOSAGR Project has been an interdisciplinary effort specifically devoted to increase the carbon sink capacity of soils by means of innovative and sustainable strategies, as they affect physical, chemical, biological, and agronomic soil quality. As a contribution to the MESCOSAGR Project, we studied, in soil microcosm experiments, the changes of selected soil chemical properties, soil CO2 efflux, and root morpho-topology after addition of either mature compost or a synthetic, water-soluble iron-porphyrin biomimetic catalyst (CAT), as single addition or in combination of the two treatments.

Enclosed model ecosystems, such as microcosms, have become a major research tool in soil ecology to enable scientific investigations in less complex ecosystems than in natural ones (Kampichler et al. 2001). Soil microcosms are nowadays increasingly being used to also investigate changes in soil CO2 emission in differing soil-plant systems under differing treatments (Smart and Penuelas 2005). Even though they suffer from disadvantages and limitations (i.e., distance from reality and scale problems), soil microcosms allow a large number of replicates in short-time periods and at reasonable costs. Moreover, they are useful for developing hypotheses about soil-plant relationships, before being further tested at the appropriate scale in field experiments (Lukkari et al. 2006). In a comparative study, Tingey et al. (2008) recently provided evidence that results from enclosed ecosystems can be extrapolated to field conditions. In fact, they found that enclosed model ecosystems displayed similar patterns as to field experiments, when measuring photosynthesis and soil respiration in a soil-litter-plant system. Finally, enclosed model ecosystems such as mesocosms or microcosms units have been efficiently used in recent studies to investigate changes in soil respiration, as induced by compost amendment, nature and properties of the growth medium, or CAT additions (Gelsomino et al. 2010; Tortorella and Gelsomino 2011).

Furthermore, direct CAT effects on seed germination, seedling establishment, and plant growth were evaluated during the early growth phases of seedlings belonging to model plant species, namely garden cress (Lepidium sativum L.), carrot (Daucus carota L.), and Arabidopsis thaliana (L.) Heynh, grown under sterile conditions. Particular attention was paid to the effects on roots, because of their well-known ability to modulate quickly their own morphology and development in response to changing conditions in soil, as well as in response to a multitude of external stimuli.

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