Humic substances from various coal sources alter 15 N-Labeled urea nitrogen distribution in soil

Le résumé fourni par la source

Humic substances (HSs) are used as urea supplements to enhance fertilizer efficiency, but their origin significantly influences the distribution of urea-derived nitrogen (N) in soils due to their distinct characteristics. This study compared the properties of HSs derived from different coal sources: fulvic acid from weathered coal (FA1) and lignite coal (FA2), and humic acid from weathered coal (HA1) and lignite coal (HA2). The distribution of urea-derived N, using 15N-labeled urea and HSs, was analyzed under flooded and 60% water-filled pore space (WFPS) conditions during a 120-day incubation. The addition of HSs, regardless of their coal source, significantly increased soil urea-derived N storage. The distribution of urea-derived soil N pools was largely determined by the structure of the HSs. In flooded treatments, FAU1, FAU2, HAU1, and HAU2 enhances urea N retention in the soil mineral N, respectively. HSs from weathered coal, which have high aromatic carbon content, afforded greater urea mineral N retention in soil compared to those from lignite coal. Under 60% WFPS, humic acid from lignite coal increases urea N remaining in soil fixed N and organic N pools, and FA from lignite coal more effectively increased soil exchangeable NO3−-N derived from urea than other HS treatments. These findings suggest that the addition of HSs can improve 15N-labeled urea N retention, but their effects on soil N pools derived from urea mitigation are influenced by both the structure of the HSs and the moisture condition. This research enhances our understanding of urea-soil N transformation and aids in optimizing HS application for improved N management.

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