Carbon-allocation dynamics in reed canary grass as affected by soil type and fertilization rates in northern Sweden

Abstract

A field experiment was conducted in northern Sweden between 1995 and 1997, with the objectives (1) to quantify the dynamics of carbon accumulation in above- and belowground crop components of reed canary grass (RCG) during the second and third year after sowing and (2) to examine the effect of fertilization and soil type (mineral vs. organic) on C allocation. Across all treatments, carbon accumulation in belowground organs in the top 20 cm was on average 3 and 3.4 Mg C by the end of the second and third year, respectively, with roots and rhizomes accounting for up to 80%. Roots contributed most to belowground C mass during the second growing season but during the preceding winter, root biomass C decreased by 44–67%, and, thereafter, during the third growing season, the proportion of rhizome C increased. The dynamics of root biomass was considerably high, suggesting high root turnover rates. Rhizomes support re-growth during spring and rhizome biomass seems to increase with crop age. Thus, early harvesting before October may impact on the productivity during the following season.

Among the factors studied, harvest date was the most influential and affected C allocation in all crop components considerably. Fertilization stimulated growth of shoots, rhizomes, and BSBs (belowground shoot bases) but not that of roots. However, root biomass was higher in the organic than in the mineral soil. In this study, we considered only plant components above 20 cm depth. More detailed studies are needed to calculate more complete soil C balances. However, high belowground biomass production and root turnover indicate a high C input to the soil, which may result in positive soil C balances. Therefore, RCG cropping could have considerable carbon-sequestration potential.