Litter Dynamics in a Green Panic (Panicum maximum var. trichoglume) Pasture in Queensland

Decline of productivity of sown pastures is related to nitrogen (N) deficiency in the presence of high C:N ratio litter. We therefore examined litter dynamics in 2 20-year•old green panic pastures (high and low N) on a clay soil. Litter inputs, decomposition in litter bags, and in sit11 changes in undisturbed litter were measured. The standing crop of coarse litter peaked in early summer and troughed in mid­winter. The N concentration was 0.60% (C:N 70), At least 1.7 t/ha of dead tops containing 0.44% N entered the litter pool in one year. Annual turnover of coane litter was c. 1.0. Rainfall controlled decay rate. In litter bags, half the fresh litter disappeared in 1 year, but N concentration doubled and 90% of the N was retained. Partially decomposed fine litter decomposed slowly. We conclude that litter dynamics contributes to the so-called run-down of ageing sown grass pastures.