Rhizodeposition and turnover of root-derived organic material in barley and wheat under conventional and integrated management

Abstract

Carbon fluxes in the rhizospherre of barley (Hordeum vulgare L.) and wheat (Triticum aestivum L.) were studied under the field conditions with conventional management (CONV) and integrated management (INT) using 14C-CO2 pulse labelling. As estimated by a model rhizodeposition technique, the bulk of the 14C soil/root respiration during a 3 week period after pulse labelling originated from root respiration and only a minor part was due to microbial activity. Root 14C losses during washing from soil considerable (up to 40%) and were corrected for. Most of the carbon transfer to the roots of barley and wheat occurred in the early developmental stages, with a maximum flux around tillering. Over the entire growing season, this amounted to 52% of the above-ground production. Of the annual root growth, about one-half was found to be decayed by the end of the growing period. Compared with CONV, in INT a lower transfer of carbon to the roots, a lower root growth and a lower total rhizodeposition was found. In winter wheat this was mainly due to a lower overall plant production, and not a different C distribution pattern. Total rhizodeposition constituted 29–50% of the carbon translocated below ground and was 1.5–2.1 times the amount of roots left at crop harvest. Microbial respiration of rhizodeposits was higher in CONV than in INT.