Litter quality impacts short- but not long-term soil carbon dynamics in soil aggregate fractions

Complex molecules are presumed to be preferentially stabilized as soil organic carbon (SOC) based on the generally accepted concept that the chemical composition of litter is a major factor in its rate of decomposition. Hence, a direct link between litter quality and SOC quantity has been assumed, accepted, and ultimately incorporated in SOC models. Here, however, we present data from an incubation and field experiment that refutes the influence of litter quality on the quantity of stabilized SOC. Three different qualities of litter (Tithonia diversifolia, Calliandra calothyrsus, and Zea mays stover; 4 Mg C.ha -1.yr-1) with and without the addition of mineral N fertilizer (0 or 120 kg N.ha-1.season-1) were added to a red clay Humic Nitisol in a 3-yr field trial and a 1.5-yr incubation experiment. The litters differed in their concentrations of N, lignin, and polyphenols with the ratio of (lignin polyphenols) :N ranging from 3.5 to 9.8 for the field trial and from 2.3 to 4.0 for the incubation experiment in the order of T. diversifolia