Root carbon input in organic and inorganic fertilizer-based systems
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Background and aims
In agroecosystems, carbon (C) inputs come from plant roots, retained shoot residues and in some cases from applied manures. Manure and shoot derived C inputs are relatively easy to determine. Conversely, high costs associated with root measurements have caused knowledge on root C input to remain scant. This study aimed at determining macro-root C input and topsoil root related respiration in response to nutrient management and soil fertility building measures.
We sampled roots and shoots of cereals and catch crops in inorganic and organic fertilizer-based arable cropping systems in a long-term experiment in 2 years, 2008 and 2010. Sampled shoots and macro-roots of catch crop mixtures and cereals were characterized for dry matter (DM) biomass (C was estimated as 45 % of DM biomass). We also measured topsoil root-related soil respiration throughout the growing season of winter wheat by subtracting soil respiration from soil with and without exclusion of roots.
Catch crop roots accounted for more than 40 % of total plant C. For spring barley in 2008 and spring wheat in 2010, root C was higher in the organic than in the inorganic fertilizer-based systems. However, for winter wheat in 2008 and spring barley in 2010, there were similar amounts of root C across systems. The measurements of topsoil root-derived respiration also showed no difference across systems, despite large differences in harvested cereal yields. Cereal biomass shoot-to-root (S/R) ratio was higher (31–131 %) in inorganic than in organic fertilizer-based systems.
Our findings show that macro-roots of both cereal crops and catch crops play a relatively larger role in organically managed systems than in mineral fertilizer based systems; and that the use of fixed biomass S/R ratios to estimate root biomass leads to erroneous estimates of root C input.
KeywordsCarbon sequestration Catch crop Root dry matter biomass Shoot dry matter biomass
- Amthor JS (2000) Plant respiratory responses to the environment and their effects on the carbon balance. In: Wilkinson RE (ed) Plant-environment interactions. Marcel Dekker, New York, pp 501–504Google Scholar
- Djurhuus J, Olesen JE (2000) Characterisation of four sites in Denmark for long-term experiments on crop rotations for organic farming. DIAS Report Plant Production No. 33Google Scholar
- Gregory P (2006) Plant roots: Growth, activity and interaction with soils. Blackwell Publishing ISBN 978-1-4051-1906-1Google Scholar
- Gyldenkærne S, Petersen BM, Olesen JE (2007) Konsekvenser og muligheder ved Danmarks deltagelse i Kyoto-protokollens artikel 3.4 på landbrugsområdet (Consequences and possibilities in participation of Denmark in the Kyoto Protocol article 3.4 within agriculture). Working Report from Environmental Protection Agency 5/2007. Ministry of Environment, CopenhagenGoogle Scholar
- Hilbert DW (1990) Optimization of plant root:shoot ratios and internal N concentration. Ann Bot 66:91–99Google Scholar
- Kalra YP, Maynard DG (1991) Methods manual for forest soil and plant analysis. Informations Report NOR-X-319. Northwest Region, CanadaGoogle Scholar
- Kang JG, van Iersel MW (2004) Nutrient solution concentration affects shoot:root ratio, leaf area ratio, and growth of subirrigated Salvia (Salvia splendens). HortSci 39:49–54Google Scholar
- Luo Y, Zhou X (2006) Soil respiration and the environment. Academic press, Elsevier, ISBN 978-0-12-088782-8Google Scholar
- Olesen JE, Askegaard M, Rasmussen IA (2000) Design of an organic farming crop-rotation experiment. Acta Agric Scand B-S P 50:13–21Google Scholar
- Oliveira MG, van Noordwijk M, Gaze SR, Brouwer SB, Mosca G, Hairiah K (2000) Auger sampling, ingrowth cores and pinboard methods In: Smit AL, Bengough AG, Engels C et al (eds) Root methods: A handbook. Springer, ISBN 3-540-66728-8, p 205Google Scholar
- Plantedirektoratet (1994) Fælles arbejdsmetoder for jordbundsanalyser. Plantedirektoratet, CopenhagenGoogle Scholar
- SAS Institute (1996) SAS/STAT™ Software: changes and enhancements through release 6.11. SAS Institute, CaryGoogle Scholar
- Schjønning P, de Jonge LW, Munkholm LJ, Moldrup P, Christensen BT, Olesen JE (2012) Drivers for dispersibility and soil friability – test of the clay carbon saturation concept. Vadose Zone J (in press)Google Scholar