Development and Verification of a Model Simulating Ammonia Volatilization from Soil and Manure

Abstract

AbstractThe VOLAT model was developed to simulate ammonia volatilization in manure and soil and to be integrated as a submodel into a larger model called Manurial Nitrogen Management: Environmental Aspects (MANIMEA). The MANIMEA model simulated the transformation and transportation processes affecting N in manure‐amended soils. A major feature of MANIMEA is that the manure and soil can be considered as separate components. This is important because manure is usually left on the soil surface for a period following application and prior to its incorporation into the soil; a significant amount of ammonia is lost by volatilization during this period. The VOLAT model was based on a nonpoint source and used a first‐order governing equation. An overall rate constant was used to take into account the effects of temperature, soil cation exchange capacity (CEC), and the air flow rate on volatilization. The VOLAT model was verified by comparing it to an analytical solution and by using experimental conditions and data given in the literature. Comparison of results demonstrated similar trends with some differences that can be attributed to the ability of VOLAT to account for variations in temperature, CEC, and air flow rates.Simulations were done for two manure application methods: surface application and injection. Results demonstrated that VOLAT rendered a simulation of N loss through volatilization that fell within acceptable limits.