Impact of climate and agricultural management practices on carbon fluxes using a CLM5 land surface model

Carbon exchange from agroecosystems contributes to the fluctuations of the carbon cycle. The present research employs the Community Land Model version 5 (CLM5) to examine the effects of climate and agricultural management methods, such as fertilization and irrigation, on carbon fluxes in the primary agroecosystems of India. In this study, CLM5 is calibrated and validated against the crop phenology dataset of spring wheat and rice. The crop phenology data is an unprecedented dataset that we have compiled by gathering information from many agricultural institutes around India. The crop dataset covers the period from 1970 to 2020. We have comprehensively tested and validated the CLM5 crop module in the Indian region. Subsequently, regional-scale simulations were conducted. The findings indicated that there are large variations in fluxes among different climatic regions of India, primarily due to disparities in growing circumstances. Throughout the study period, all fluxes exhibited statistically significant upward trends (p<0.1). Further numerical experiments are performed to examine the potential impact of natural factors, such as variations in temperature and levels of carbon dioxide (CO2), as well as agricultural techniques like nitrogen fertilizer and water availability, on the previously observed upward trends. The tests demonstrated that elevated levels of carbon dioxide (CO2), nitrogen fertilization, and irrigation water resulted in heightened carbon fluxes, with nitrogen fertilization exerting the most pronounced impact.