The 14C tracer study of carbon turnover in soil in a model experiment

The translocation of carbon to the soil by lettuce (Lactuca sativa L.) was studied by the C-14 pulse labeling technique. Carbon dioxide fluxes from the soil were measured over 12 days. Between 20 and 35% of the assimilated labeled carbon was found in the lettuce leaves, 1.5-5% in the roots, and about 5-8% was released as CO2 from the rhizosphere. The 60-day-old lettuce plants transferred 120-160 kg C/ha to the soil. Lettuce cultivation resulted in an accelerated decomposition of soil organic matter by a factor of 1.5-3.