Abstract
Urea (U) is the most important nitrogen (N) fertilizer in agriculture worldwide, and as N fertilizer can result in large gaseous losses of NH3 and N2O. Thus, urease inhibitors (UIs) and nitrification inhibitors (NIs) have been coupled with U fertilizers to mitigate NH3 and N2O emissions. However, it is still unclear whether adding NIs and/or UIs to U stimulates other pollutants, while reducing one pollutant. Furthermore, part of the NH3 deposition to earth is converted to N2O, leading to indirect N2O emission. To estimate direct and indirect effect of UIs and NIs on the N2O-N and NH3-N losses from U; therefore, we analyzed multi-year field experiments from the same site during 2004 to 2005 and 2011 to 2013. The field experiments with U fertilization with or without UI (IPAT, N-isopropoxycarbonyl phosphoric acid triamide) and NI (DCD/TZ, Dicyandiamide/1H-1, 2, 4-Triazol) in winter wheat and with calcium ammonium nitrate (CAN) were conducted in southern Germany. Fluxes of NH3 or N2O emissions were determined following each split N fertilization in separate experiments on the same site. Our results showed that U with NIs considerably reduced N2O emissions, and adding UIs decreased NH3 emissions. However, the effect on N2O emissions exerted by (U + UIs) or (U + UIs + NIs) was inconsistent. In contrast to the treatment of (U + UIs + NIs), the addition of NIs alone to U stimulated NH3 emission compared to treatment with U. When 1% indirect N2O emission from NH3 (IPCC emission factor (EF4)) was considered to estimate the indirect N2O emission, total N2O emissions from (U + NIs) were approximately 29% compared to that from U alone and 36% compared to that from (U + UI), indicating that indirect N2O emission from NH3 induced by NIs may be negligible.
Highlights
IntroductionA large quantity of mineral nitrogen (N) fertilizer was produced using the
Over the past century, a large quantity of mineral nitrogen (N) fertilizer was produced using theHaber–Bosch process that converts atmospheric N2 to ammonia (NH3 ) in order to meet the rapid increase in population for food production [1]
The results in this study showed an emission factor of 4.5% of the applied N based on the average of a two-year study (Table 6), which was lower than the NH3 emission from U
Summary
A large quantity of mineral nitrogen (N) fertilizer was produced using the. Haber–Bosch process that converts atmospheric N2 to ammonia (NH3 ) in order to meet the rapid increase in population for food production [1]. In mineral N fertilizer production, the use of urea (U). Urea is the most important N fertilizer in the world, accounting for 55% of mineral N fertilizer production in 2018, and U is expected to increase to Atmosphere 2020, 11, 782; doi:10.3390/atmos11080782 www.mdpi.com/journal/atmosphere. There are problems resulting from large gaseous losses using U as an N fertilizer, which are due to the increase in pH resulting from U hydrolysis. There is consensus regarding the higher ammonia emissions resulting from U fertilization compared to those of CAN, there are contrasting reports regarding N2 O losses of these fertilizers [4]. There is a need to further compare N2 O emissions from U to those of CAN
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