Potential ammonia volatilization from 39 different novel biobased fertilizers on the European market – A laboratory study using 5 European soils

Current political focus on promoting circular economy in the European Union drives great interest in developing and using more biobased fertilizers (BBFs, most often waste or residue-derived). Many studies have been published on environmental emissions, including ammonia (NH₃) volatilization from manures, but there have only been a few such studies on BBFs. Ammonia volatilization from agriculture poses a risk to the environment and human health, causing pollution in natural ecosystems when deposited and formation of fine particulate matter (PMₓ). Furthermore, NH₃ volatilization results in removal of plant-available N from agricultural systems, constituting an economic loss for farmers. The aim of this laboratory study was to determine the potential NH₃ volatilization from 39 different BBFs commercially available on the European market. In addition, this study aimed to investigate the effect of incorporation, application rate, soil type, and soil moisture content on potential NH₃ volatilization in order to derive suggestions for the optimal field application conditions. Results showed a great variation between BBFs in potential NH₃ volatilization, both in terms of their temporal pattern of volatilization and amount of NH₃ volatilized. The potential NH₃ volatilization varied from 0% of applied total N (olive oil compost) to 64% of applied total N (manure and crop digestate) during a 27- or 44-day incubation period. Characteristics of BBFs (pH, NH₄⁺-N, NO₃⁻-N, DM, C:N) and their interaction with time could explain 89% of the variation in accumulated potential NH₃ volatilization. Incorporation of BBFs into an acidic sandy soil effectively reduced potential NH₃ volatilization by 37%–96% compared to surface application of BBFs. Potential NH₃ volatilization was not significantly affected by differences in application rate or soil moisture content, but varied between five different soils (with different clay and organic matter content), with the highest NH₃ volatilization potential from the acidic sandy soil.