A dynamical process-based model for quantifying global agricultural ammonia emissions - AMmonia-CLIMate v1.0 (AMCLIM v1.0) - Part 1: Land module for simulating emissions from synthetic fertilizer use

Ammonia (NH3) emissions mainly originate from agricultural practices and can have multiple adverse impacts on the environment. With the substantial increase in synthetic fertilizer use over the past decades, volatilization of NH3 has become a major loss of N applied to land. Since NH3 can be strongly influenced by both environmental conditions and local management practices, a better estimate of NH3 emissions from fertilizer use requires improved understanding of the relevant processes. This study describes a new process-based model, AMmonia-CLIMate (AMCLIM), for quantifying agricultural NH3 emissions. More specifically, the present paper focuses on the development of a module (AMCLIM-Land) that is used for simulating NH3 emissions from synthetic fertilizer use. Other modules, together termed as AMCLIM-Livestock, simulate NH3 emissions from agricultural livestock and are described in Part 2). AMCLIM-Land dynamically models the evolution of N species in soils by incorporating the effects of both environmental factors and management practices to determine the NH3 emissions released from the land to the atmosphere. Based on simulations for 2010, NH3 emissions resulting from the synthetic fertilizer use are estimated at 15.0 Tg N yr-1, accounting for around 17 % of applied fertilizer N. Strong spatial and seasonal variations are found. Higher emissions typically occur in agriculturally intensive countries (such as China, India, Pakistan and the US) and mostly reach the maximum in the summer season. Volatilization rates indicate that hotter environments can result in more N lost due to NH3 emissions and show how other factors including soil moisture and pH can greatly affect volatilization of NH3. The AMCLIM model also allows for estimation of how application techniques and fertilizer type have impacts on the NH3 emissions, pointing to the importance of improving management practices to tackle nutrient loss and of appropriate data gathering to record management practices internationally.