Effects of urea enhanced with different weathered coal-derived humic acid components on maize yield and fate of fertilizer nitrogen

Humic acid (HA) is a readily available and low-cost material that is used to enhance crop production and reduce nitrogen (N) loss. However, there is little consensus on the efficacy of different HA components. In the current study, a soil column experiment was conducted using the 15N tracer technique in Dezhou City, Shandong Province, China, to compare the effects of urea with and without the addition of weathered coal-derived HA components on...