Carbon mineralization in soil of roots from twenty crop species, as affected by their chemical composition and botanical family

Our objective was to relate chemical composition of roots of a wide range of annual crops to root decomposition, so as to assess roots potential contribution to soil carbon (C). Roots from 20 different crops and 4 botanical families, collected under field conditions were incubated in soil for 120 days at 25 A degrees C. The initial chemical composition of roots was determined. The C mineralization was assessed by the continuous measurement of CO2 release and using single exponential model. PCA analysis was used to explore qualitative pattern in root quality and decomposition. PCA analysis showed that chemical characteristics (traits) differentiated plant families. The mineralization of root C varied greatly in terms of kinetics and in the total amount of C mineralized (36 % to 59 % of added C). Mineralization constant (k value) was negatively correlated with hemicelluloses and positively with N content. Poaceae roots that combined high hemicelluloses, low cellulose and low total N, showed low degradation rate and cumulative C mineralization. The chemical composition of roots, as for the above-ground parts of plants, can correctly predict their rate of decomposition in soils. The taxonomic affiliation enhances the understanding of the chemical determinants of quality of roots.