Abstract:
Farmland N
2O emission is a hot topic in current climate change research. Climate change (elevated CO
2 concentration and increased temperature) and farmland management measures are the key factors affecting N
2O emission in soil. Slow-release fertilizers are considered to have a positive effect on reducing N
2O emissions. It is unclear how the interaction between climate change and slow-release fertilizers would affect N
2O emissions, thus we innovatively combined the local two crop cultivation model to investigate the potential impact of applying slow-release fertilizers on soil N
2O emissions during the growing season of subsequent crops under celevated CO
2 concentration and increased temperature. In this study, two air temperatures (ambient temperature and ambient temperature +2℃) and two CO
2 concentrations (400 μmol mol
−1 and 600 μmol mol
−1) were set in the controlled chambers. Two types of fertilizers (conventional urea and slow-release urea) were applied during the wheat season under various environmental treatments in the wheat soybean rotation system, and no fertilizer was applied during the soybean growing season. CK referred to the ambient environmental CO
2 concentration and temperature simulated in the controlled chamber (the ambient environmental CO
2 concentration in this experiment was 400 μmol mol
−1, and the environmental temperature was controlled by the intelligent control system to be consistent with the external environment). N
2O emission during the whole growth period of soybean season, the contents of soil ammonium nitrogen and nitrate nitrogen, and the activities of enzyme involved in nitrification and denitrification at drumming stage and ripening stage in soybean-grown soil were measured. The results indicated that N
2O emissions in soybean-grown soil were mainly concentrated in the later growth period of soybean. Compared with the application of conventional urea, the application of slow-release fertilizer in wheat-grown soil reduced the total N
2O emissions by 38.46% in soybean growth period under increased temperature (ET) alone, while the application of slow-release fertilizer increased the total N
2O emissions in soybean-grown soil by 80.76%, 82.75%, and 11.96% under CK, elevated CO
2 concentration (EC) alone, and co-elevation of atmospheric CO
2 concentration and temperature (ECT) treatments, respectively. Compared with CK treatment, ET accelerated the conversion of ammonium nitrogen to nitrate nitrogen in soybean-grown soil at filling stage, thereby promoting nitrate reductase activity and increasing N
2O emissions. In addition, EC alone had no effect on N
2O emissions in soybean-grown soil compared with CK treatment. ECT resulted in a slight increase in nitrate and ammonium nitrogen content in soybean-grown soil compared with CK treatment, which mainly attributed to the increase in nitrate reductase activity that might promote N
2O emissions, but there was no significant difference in N
2O emissions in soybean-grown soil when ECT compared with ET under conventional urea. In conclusions. N
2O emission will not increase with elevated CO
2 concentration alone. N
2O emissions will increase under elevated temperature in the future, and the rational application of slow-release fertilizer in wheat-grown soil can increase the available nitrogen content in the soil, thus reducing N
2O emission in soybean-grown soil. Our study highlights that slow-release fertilizer hold a greater potential of reducing N
2O emission under climate change scenarios.