Effects of phosphorus application on CH4 fluxes in an Acacia mangium plantation with and without root exclusion

The application of phosphorus (P) fertilization on industrial tropical leguminous forest plantations may affect methane (CH4) exchange between the soil surface and the atmosphere, by influencing microbial methanotrophic and methanogenesis activity and root growth. In this study, we examined the effects of P fertilization on CH4 fluxes in an Acacia mangium plantation in South Sumatra, Indonesia. To understand the role of microbial and plant root activities separately, we prepared both root-excluded and root-existing plots. Two-way (root exclusion and P application) ANOVA showed that P application significantly stimulated the CH4 uptake at day 106 (P=0.032), and tended to stimulate mean CH4 uptake during the experiment (P=0.071). The result could be attributed to stimulated methanotrophic activites and/or inhibited methanogenesis activities by P application. However, the change in CH4 fluxes by P application was not clear in the root-existing plots. These results imply that, in the root-existing plots, the effects of P application might be reduced by P utilization by root or stimulated methanogenesis by increased carbon supply of root residue. We suggest that the effects of P application on CH4 fluxes in a tropical leguminous plantation are trivial.