Relations of shoot C, root C and root length with root-released C of two barley cultivars and the decomposition of root-released C in soil

The production and utilization of root-derived C is fundamental to the functioning of ecosystems. The objectives of this experiment were to quantify the amount of root-released C produced by two barley (Hordeum vulgare L.) cultivars, to evaluate the direct and indirect effects of shoot C, root C and root length on the root-released C and to quantify the kinetics of the decomposition of root-released C in soil for two barley cultivars. Seedlings of two barley cultivars, Abee and Samson, were cultured in nutrient solution for 20 d and then pulse-labelled with 14 C for 5 d. Samson released more C than Abee during the entire experimental period. Root length had the greatest direct effect on root-released C for the two barley cultivars. Kinetics analysis of the decomposition of root-released C added to soil showed that the labile components of the added material was 87.3% for Abee and 74.4% for Samson with half-lives of 4.3 d and 4.5 d, respectively. The half-lives of the resistant components of the root-released C added to soil and microbially-derived material were 37.7 d for Abee and 29.6 d for Samson, respectively. The amount of root-released C and its decomposition rate in soil varied with cultivars used.