Biomass production and nutrient cycling in Eucalyptus short rotation energy forests in New Zealand: II. Litter fall and nutrient return

Litter fall and nutrient return via the litter fall were measured during the first 3-yr rotation of three Eucalyptus short rotation forest species (E. botryoides, E. globulus and E. ovata) irrigated with meatworks effluent compared with no irrigation. Up to 13.4 oven dry t/ha/yr of annual litter fall was recorded with nutrient returns of up to 159 kg N/ha/yr, 9 kg P/ha/yr, 28 kg K/ha/yr, 125 kg Ca/ha/yr, 22 kg Mg/ha/yr, and 32 kg Mn/ha/yr. Effluent irrigation increased the litter fall and the return of some nutrients. More litter fall with higher nutrient return was found under E. globulus than under the other two species. However, the amounts of litter fall and nutrient return were highly dependent on the degree of biomass production and nutrient uptake. During the 3-yr period, up to 20% of the total above ground biomass produced was in the form of litter, and via the litter fall, up to 24% of the total N uptake was returned to the soil surface.