Abstract
Forest fine root litter enters agricultural soils in some cases and its decomposition would change the soil's properties. However, how this process further influences the ammonia (NH(3)) volatilization and nitrous oxide (N(2)O) emission from agricultural soil receiving fertilizer nitrogen (N) is unknown. Here, we conducted a soil pot experiment to investigate the responses of the aforementioned gaseous N losses during wheat season to fine root litters derived from Populus deltoides (RP) and Metasequoia glyptostroboides (RM) incorporations. The results showed that two forest fine root litters reduced total NH(3) losses by 30.6-31.9% from 180 kg N ha(-1) applied to farmland soil, and this effect was attributed to decreased soil urease activity and ammonium-N during the basal N fertilization period. Whether receiving fertilizer N or not, N(2)O emissions from farmland soil were significantly (p < 0.05) mitigated by 62.8-68.2% and 43.0-50.0% following the RP and RM incorporation, respectively. Lower N(2)O emission was ascribed to increased soil pH but decreased soil nitrate-N and bulk density. In addition, less AOA and AOB amoA but more nosZ gene abundances explained the fine root litter-induced N(2)O mitigation effect. Neither forest fine root litter exerted a negative effect on wheat grain yield and crop N use efficiency in N-added agriculture soil. In conclusion, forest fine root litter incorporation could help to mitigate gaseous N losses via NH(3) volatilization and N(2)O emission from fertilizer-N-applied agricultural soils, and without crop production loss.