Abstract
AimsExtensive knowledge of perennial forage root systems is essential, given their critical role in below-ground C input.MethodsRoot length and diameter were quantified periodically from 2016 to 2018 with minirhizotrons in a field experiment with three forage management systems: mixture of timothy (Phleum pratense L.) and tall fescue (Festuca arundinacea Schreb.) fertilized with (i) dairy cattle slurry or (ii) calcic ammonium nitrate, and (iii) mixture of timothy, tall fescue, and alfalfa (Medicago sativa L.) without N fertilization. Root biomass was measured yearly by coring.ResultsManagement systems with the two fertilization sources did not differ in root elongation, but the management system with alfalfa resulted in a slower root elongation after the first defoliation and a lower root mortality in the fall. Root length turnover was greater in the topsoil with dairy cattle slurry than with calcic ammonium nitrate. Fine roots dominated the surface soil and coarse roots the deeper soil layers.ConclusionsRoot growth and mortality were more contrasted between systems that differed by the presence of alfalfa than by fertilizer source. As many root characteristics are drivers of soil C storage, the choice of perennial species in mixtures appears as a key management factor for sustainable farming systems.
Highlights
Root-related ecosystem services provided by perennial forage crops are fundamental to the sustainability of modern farming, especially for livestock-based systems (Gregory et al 2013; Ojeda et al 2017; Soussana et al 2014)
Root growth and mortality were more contrasted between systems that differed by the presence of alfalfa than by fertilizer source
This study improves our understanding of many important drivers of C dynamics in soils under perennial crops, especially those affecting C inputs such as root elongation, mortality, turnover, and depth distribution
Summary
Root-related ecosystem services provided by perennial forage crops are fundamental to the sustainability of modern farming, especially for livestock-based systems (Gregory et al 2013; Ojeda et al 2017; Soussana et al 2014). The trait-based approach is usually favoured by plant ecologists to assess functions, changes, and shifts in plant tissues in response to environmental gradients in ecosystems and to estimate the effect of these changes on ecosystem functioning This approach is well-suited for agroecosystems in order to understand how management practices influence ecosystem processes such as soil C storage and nutrient cycling (Bardgett et al 2014; De Deyn et al 2008; Martin and Isaac 2015), and promote sustainable agricultural intensification (Faucon et al 2017). Root biomass combines two “functional compartments”, namely the acquisitive fine, short-lived, and absorptive roots, and the conservative thick roots and rhizomes dedicated to water transport and resource storage (Klimesova et al 2018) These two types of roots could contribute in different ways to below-ground C input (Freschet et al 2017; Poirier et al 2018). Legumes and grass-legume mixtures were overlooked, while they are thought to induce different rooting patterns than grasses (Hernandez and PiconCochard 2016)
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