Photoassimilated carbon allocation in a wheat plant-soil system as affected by soil fertility and land-use history

Carbon (C) cycling in terrestrial ecosystems is influenced by the distribution of photo-assimilated C in the plant-soil system. Photo-assimilated C allocation in a wheat cropping system was examined to identify the links between soil fertility, C partitioning and soil C sequestration. A pulse labelling experiment was conducted where (CO2)-C-14 was introduced to wheat plants grown in two groups of soils of varying fertility: arable soils spiked with nutrients, and soils with differing land-use histories. Wheat shoot, root and soil samples were taken 1, 14 and 28 days after pulse labelling to examine the fluxes of C-14 in the plant-root-soil system. The partitioning of C-14 in wheat plant-root-soil system was found to vary with time, nutrient spiked soil fertility and land-use history. At the end of the experiment using spiked soils, a positive correlation was observed between the allocation of C-14 in the shoots and soil fertility, whereas in the roots, this relationship was negative. The overall allocation of C-14 in the plant-root system differed significantly between the land-use histories; while in the spiked arable soils C-14 allocation in the shoots and roots systematically followed their fertility status. There was a weak relationship between C allocation and soil fertility in the soils of different land-use history compared to the strong relationship in the spiked arable soils. This suggests that other factors in the soils under different land uses were more important than nutrient status alone in driving photo-assimilated C allocation. This study demonstrated that soil fertility and land-use history have a crucial role in the allocation of photo-assimilated C in the plant-soil system and are important factors by which C sequestration in soil may be impacted.