# Forest Fine Root Litter Mitigates the NH3 Volatilization and N2O Emission from N-Applied Agriculture Soil

## TL;DR

Forest fine root litter can reduce ammonia and nitrous oxide emissions from fertilized agricultural soils without harming crop yields.

## Contribution

This study reveals that forest fine root litter mitigates gaseous nitrogen losses in agricultural soils without affecting crop productivity.

## Key findings

- Forest fine root litter reduced ammonia losses by 30.6−31.9% in fertilized soils.
- N2O emissions were reduced by 62.8–68.2% with Populus deltoides litter and 43.0−50.0% with Metasequoia glyptostroboides litter.
- Soil pH increase and reduced nitrate-N and bulk density explained the lower N2O emissions.

## 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 (NH3) volatilization and nitrous oxide (N2O) 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 NH3 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, N2O 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 N2O 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 N2O 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 NH3 volatilization and N2O emission from fertilizer-N-applied agricultural soils, and without crop production loss.