Abstract: This study aimed to (1) quantify the impact of different cropping systems on greenhouse gas emission amount and intensity in North China Plain under climate change, (2) clarify the spatial variations of annual yields, resource use efficiencies and greenhouse gas emissions in North China Plain under different water and nitrogen managements, (3) provide a scientific basis for the smart water and nitrogen managements of main cropping systems in North China Plain to adapt to climate change. Based on the meteorological data, soil data and crop data of 44 meteorological stations in North China Plain from 1981 to 2020, the agricultural production systems sIMulator (APSIM) model was used to simulate the yield and greenhouse gas emissions of spring maize single-cropping and wheat-maize double-cropping systems in North China Plain. The changes of greenhouse gas emissions with the increase of annual yield in wheat-maize double-cropping system compared with spring maize single-cropping system were analyzed. On this basis, APSIM model was used to simulate the annual yields and greenhouse gas emissions of wheat-maize double-cropping system in North China Plain under different water and nitrogen managements, and their agronomic efficiencies of applied N and water productivities were also calculated. Besides, the normalization method was adopted to clarify whether each management achieve the multi-objective synergistic effects of high annual yield, high resource use efficiency and low greenhouse gas emission. In addition, the smart water and nitrogen managements for main cropping systems to adapt to climate change in the study area were proposed. The results showed that：(1) from 1981 to 2020, the annual greenhouse gas emission amount of spring maize single-cropping system in the study area was 0.48×104−1.65×104kg CO2-eqha−1, while the annual greenhouse gas emission amount of wheat-maize double-cropping system was 2.36×104−4.11×104kg CO2-eqha−1. The greenhouse gas emission amount of wheat-maize double-cropping system increased by 406.7% compared with that of spring maize single-cropping system in the study area. (2) From 1981 to 2020, the greenhouse gas emission intensity of spring maize single-cropping system in the study area was 0.08−0.35kg CO2-eq  kg−1, while the greenhouse gas emission intensity of wheat-maize double-cropping system was 0.19−0.47kg CO2-eqkg−1. The greenhouse gas emission intensity of wheat-maize double-cropping system increased by 153.8% compared with that of spring maize single-cropping system in the study area. (3) With the increase of irrigation amount of winter wheat, annual yields and greenhouse gas emissions of wheat-maize double-cropping system increased. However, irrigation stage of winter wheat had no significant effect on annual yields and greenhouse gas emissions. (4) The annual yields and greenhouse gas emissions increased significantly with the increase of nitrogen application when the total nitrogen application of each crop was 0−225kgha−1 for wheat-maize double-cropping system. However, once the total nitrogen application of each crop reached 225kgha−1 for wheat-maize double-cropping system in North China Plain, the annual yields had no significant change but the greenhouse gas emissions still significant increased with the increase of nitrogen application of each crop. The results indicate that the adoption of climate-smart water-nitrogen managements can achieve both high annual yield and relatively low greenhouse gas emissions in wheat-maize double-cropping system in North China Plain.

Key words: Climate-smart, Greenhouse gas, Cropping system, Water and nitrogen managements, North China Plain