Litter dynamics of low and high tannin sericea lespedeza plants under field conditions

Sericea lespedeza [Lespedeza cuneata (Dum. Cours) G. Don.] is a perennial legume with high polyphenol (tannin) concentration. The decomposition and nutrient release of sericea lespedeza residues with two tannin levels (high = 22% or low = 16%), which were either placed on the soil surface or buried at a depth of 5 cm were studied. An experiment was carried out at two sites for 2 yr. Litter mass loss and nutrient (N, P, K, Ca, Mg, Cu, Fe, Mn, Zn, B, Mo, Co) release were recorded. Litter mass loss was higher for the low-tannin residues and for those buried. From the beginning of the experiments, the C : N ratio was lower than 25 : 1 and N was mineralized for most of the studied cases; this means that N increased in availability to plants. The release of the rest of the studied nutrients was higher at the depth of 5 cm than on the soil surface and higher for low-tannin residues than for high-tannin. The observed accumulation of some nutrients in the first months presumably depended on microbial activity. The rate of release was higher for the macronutrients than for the micronutrients, with the exception of B, which had the same behaviour as the macronutrients.