Tree-based intercropping may reduce, while fertilizer nitrate may increase, soil methane emissions

Abstract

Tree-based intercropping (TBI) systems have shown some promise in mitigating greenhouse gas emissions, such as by sequestering carbon and decreasing soil nitrous oxide emissions. However, the effects of TBI on soil methane fluxes remain unknown. In a field study, we failed to show differences in soil CH4 production between TBI and conventional monocropping (CM) systems. Within TBI plots, however, we found significantly lower CH4 concentrations near the middle of the alleys than closer to tree rows. Soil CH4 concentrations also decreased with soil depth, even dipping below mean global atmospheric concentrations. Laboratory assays revealed a higher CH4 oxidation potential in soils collected from TBI plots compared with CM plots. These assays also revealed a decrease in CH4 oxidation potential after soils were amended with nitrate. We conclude that TBI could potentially reduce soil CH4 emissions, whereas fertilizer nitrate may increase them.