Effects of landfill leachate on growth and nitrogen fixation of two leguminous trees (Acacia confusa, Leucaena leucocephala)

The influence of landfill leachate on the rhizobia-legume systems of Acacia confusa and Leucaena leucocephala was assayed for five months with a serial dilution (73-0.58%) of leachate which had a high concentration of NH₄-N and dissolved organics. Although the acetylene reduction activity (ARA) of the nodules was suppressed by the leachate, the harvestable biomass of inoculated seedlings was higher than rhizobia-free seedlings. The total N content in rhizobia-free seedlings was higher than that for inoculated seedlings, indicating that the legumes accumulated more N from leachate- irrigated soil when they were not inoculated. Their performance was compared with that of two non-legumes (Cinnamomum parthenoxylon, Tristania conferta). These two non-legumes tolerated the highest concentration of leachate for only one month and then started to wilt. The total N contents of their tissue were less than those of the two legumes.