The rise in atmospheric CO2 is creating alarming environmental impacts, fostering the replacement of fossil fuels by renewable energy sources, in order to sequester C into the soil. Root morphology and distribution in the soil profile is deeply involved in crop ability to support yield under stress conditions, and recent studies have demonstrated that deeper root systems favour soil carbon storage. Aim of this research was to describe the root shape in two sorghum genotypes and to test their potential ability to resist dry conditions and to store carbon into the soil. A field experiment was carried out in 2008 in Cadriano (BO), with a two factor (genotype and soil depth) split-plot design on four blocks. Two sorghum hybrids were compared: B133 and Trudan Headless (TH), the former a typical fibre sorghum; the latter a forage genotype. At crop harvest (Sept. 22), soil core 1.2 m deep were collected, divided into 0.2 m segments and freeze-stored. Afterwards, Roots Length Density (RLD; cm cm-3), was analyzed after roots scanning. Then the samples were dried at 105° C to determine the Root Dry Weight (RDW; kg ha-1). RLD and RDW data were fitted using an equation describing root shape as a function of soil depth: Y = 1− βd. The closer to 1 the β value, the more even is the distribution along soil profile. Root morphology significantly varied between the two genotypes in the top layer, where TH exhibited a much higher RLD than B133. This difference faded in the deeper layers, where the two genotypes averaged the same RLD. A similar trend was shown for RDW), although the difference between TH and B133 in the top layer was not so large as for the previous trait. As a whole, B133 had 42% and 48% of the root system in the top third of soil profile (0.4 m), respectively in terms of root density (RLD) and biomass (RDW). Conversely, in the same profile TH was proportionally more expanded (60% of the total RLD) than heavy (45% of the total RDW), indicating an increased root biomass in the deeper layers (0.4-1.2 m). Considering the whole profile, TH had a more expanded (+29%) and heavier (+27%) root system than B133. Fitting the equation, RLD β resulted significantly higher (P ≤ 0.01) in B133 than in TH; this means a more even distribution in the former than in the latter hybrid, which may counterbalance B133 lower density over the whole profile. Conversely, RDW β did not significantly vary between TH and B133; therefore, TH advantage over B133 in terms of overall RDW was not offset by a less favourable distribution. This translates into a higher potential of C storage into the soil, counterbalancing soil organic matter mineralization (Ma et al., 2000) and easing crop access to deep water and nutrient resources. On concluding. two morphologically-different genotypes of biomass sorghum exhibited major differences in root system density and growth only in the top 0.2 m soil. Both appeared basically well fit for cropping with low nutrient and water inputs, but the forage genotype (TH) seemed potentially better suited for a storage of carbon in the soil profile, than the fibre genotype (B133).

Root shape characterization in two sorghum genotypes

ZATTA, ALESSANDRO;VECCHI, ANGELA;PRITONI, GIUSEPPE;MONTI, ANDREA;BARBANTI, LORENZO
2010

Abstract

The rise in atmospheric CO2 is creating alarming environmental impacts, fostering the replacement of fossil fuels by renewable energy sources, in order to sequester C into the soil. Root morphology and distribution in the soil profile is deeply involved in crop ability to support yield under stress conditions, and recent studies have demonstrated that deeper root systems favour soil carbon storage. Aim of this research was to describe the root shape in two sorghum genotypes and to test their potential ability to resist dry conditions and to store carbon into the soil. A field experiment was carried out in 2008 in Cadriano (BO), with a two factor (genotype and soil depth) split-plot design on four blocks. Two sorghum hybrids were compared: B133 and Trudan Headless (TH), the former a typical fibre sorghum; the latter a forage genotype. At crop harvest (Sept. 22), soil core 1.2 m deep were collected, divided into 0.2 m segments and freeze-stored. Afterwards, Roots Length Density (RLD; cm cm-3), was analyzed after roots scanning. Then the samples were dried at 105° C to determine the Root Dry Weight (RDW; kg ha-1). RLD and RDW data were fitted using an equation describing root shape as a function of soil depth: Y = 1− βd. The closer to 1 the β value, the more even is the distribution along soil profile. Root morphology significantly varied between the two genotypes in the top layer, where TH exhibited a much higher RLD than B133. This difference faded in the deeper layers, where the two genotypes averaged the same RLD. A similar trend was shown for RDW), although the difference between TH and B133 in the top layer was not so large as for the previous trait. As a whole, B133 had 42% and 48% of the root system in the top third of soil profile (0.4 m), respectively in terms of root density (RLD) and biomass (RDW). Conversely, in the same profile TH was proportionally more expanded (60% of the total RLD) than heavy (45% of the total RDW), indicating an increased root biomass in the deeper layers (0.4-1.2 m). Considering the whole profile, TH had a more expanded (+29%) and heavier (+27%) root system than B133. Fitting the equation, RLD β resulted significantly higher (P ≤ 0.01) in B133 than in TH; this means a more even distribution in the former than in the latter hybrid, which may counterbalance B133 lower density over the whole profile. Conversely, RDW β did not significantly vary between TH and B133; therefore, TH advantage over B133 in terms of overall RDW was not offset by a less favourable distribution. This translates into a higher potential of C storage into the soil, counterbalancing soil organic matter mineralization (Ma et al., 2000) and easing crop access to deep water and nutrient resources. On concluding. two morphologically-different genotypes of biomass sorghum exhibited major differences in root system density and growth only in the top 0.2 m soil. Both appeared basically well fit for cropping with low nutrient and water inputs, but the forage genotype (TH) seemed potentially better suited for a storage of carbon in the soil profile, than the fibre genotype (B133).
Proceedings of "Agro 2010 the XIth ESA Congress"
595
596
Zatta A.; Vecchi A.; Pritoni G.; Monti A.; Barbanti L.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11585/92644
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