Impacts of monoculture cropland to alley cropping agroforestry conversion on soil <scp>N<sub>2</sub>O</scp> emissions
Guodong Shao, Guntars O. Martinson, Marife D. Corre, Jie Luo, Dan Niu, Xenia Bischel, Edzo Veldkamp
Abstract
Abstract Monoculture croplands are a major source of global anthropogenic emissions of nitrous oxide (N 2 O), a potent greenhouse gas that contributes to ozone depletion. Agroforestry has the potential to reduce N 2 O emissions. Presently, there is no systematic comparison of soil N 2 O emissions between cropland agroforestry and monoculture systems in Central Europe. We investigated the effects of converting the monoculture cropland system into the alley cropping agroforestry system on soil N 2 O fluxes at three sites (each site has paired agroforestry and monoculture) in Germany, where agroforestry combined crop rows and poplar short‐rotation coppice (SRC). We measured soil N 2 O fluxes monthly over 2 years (March 2018–January 2020) using static vented chambers. Annual soil N 2 O emissions from agroforestry ranged from 0.21 to 2.73 kg N ha −1 year −1 , whereas monoculture N 2 O emissions ranged from 0.34 to 3.00 kg N ha −1 year −1 . During the rotation of corn crop, with high fertilization rates, agroforestry reduced soil N 2 O emissions by 9% to 56% compared to monocultures. This was mainly caused by low soil N 2 O emissions from the unfertilized agroforestry tree rows. Soil N 2 O fluxes were predominantly controlled by soil mineral N in both agroforestry and monoculture systems. Our findings suggest that optimized fertilizer input will further enhance the potential of agroforestry for mitigating N 2 O emissions.