Phosphorus application reduces N2O emissions from tropical leguminous plantation soil when phosphorus uptake is occurring

Abstract

We examined the effects of phosphorus (P) fertilization on N2O emissions from an Acacia mangium plantation in Indonesia. We focused on the roles of microbial and plant root activities using a trenching method to prepare root-excluded and root-including plots. In root-excluded plots, P application did not change the amount of N2O emissions. By contrast, in root-including plots, P application significantly reduced N2O emissions (from 71.1 ± 20.2 to 19.3 ± 5.1 mg N m−2 106 days−1). Lower total P, Bray-2 P, and Bio-P (microbial P determined by chloroform fumigation extraction method) contents in the soils of root-including plots as compared to root-excluded plots a few days after P application shows that acacia trees absorbed P fertilizer rapidly. This rapid P uptake probably relieved the P limitation of acacia and might have consistently increased root N uptake. This interpretation is supported by lower inorganic N content in P-applied soils (the average of three sampling times is 8.9 and 11.3 μg N g soil−1 in P-applied soils and soils without P application, respectively), which in turn decreased N2O emissions. Our study suggests that P fertilizer suppresses N2O emissions from tropical leguminous forest plantations.