Direct measurements unveil overestimations in nitrous oxide emissions from legume-based strip intercropping

Abstract

Accurate evaluation of greenhouse gas (GHG) emissions from legume-based intercropping is key to supporting the agricultural green transition. However, current methods often ignore the direct emissions from the interspecific interaction row of legume/cereal intercropping. Here, a two-year field experiment was conducted to evaluate the difference between direct measurement and theoretical estimation of N₂O emissions and soil respiration from maize/peanut and maize/soybean strip intercropping. Results showed that theoretical estimation overestimated the N₂O emissions from interaction row by 12 – 15 % compared to direct measurement (P < 0.05). This overestimation occurred mainly during the N₂O emissions peak (lasting 5 – 7 days) after topdressing N fertilization, which accounted for 21 – 49 % of the overestimation. Soil NH₄⁺ and NO₃^- concentrations in the interaction row were 33 – 129 % and 26 – 96 % lower than the weighted average of the crop rows following topdressing N fertilization (P < 0.05). However, the soil respiration of the interaction row did not differ between direct measurement and theoretical estimation, which may indicate N is the key interaction elements for intercropped legume and cereal rather than carbon. Furthermore, the uncertainty in theoretical estimation of N₂O emissions from legume-based intercropping was increases with the decrease of strip width, which mainly due to the increasing contribution of interaction zone. In conclusion, theoretical estimation can lead to an overestimation of N₂O emissions, underscoring the necessity for direct measurement, especially as strip width narrows with increased proportion of interspecific interactions zones.