Doctor of Philosophy (PhD)


School of Plant, Environmental, and Soil Sciences

Document Type




Forage systems are important for animal production. Nitrogen fertilization and herbicides use has led to a significant increase in forage production. Therefore, this study aimed to investigate the effects of biochar and N-(n-butyl) thiophosphoric triamide + dicyandiamide (NBPT+DCD) application on manure and urea fertilized soil by focusing on nitrogen fertilizer efficiency use, greenhouse gases emissions, microbial community, soil aggregate stability, and organic carbon functional groups. In addition, herbicides effect on greenhouse gases emission was assessed. Biochar and NBPT+DCD increased nitrogen use efficiency of both fertilizers managements and reduced the N2O emissions following manure fertilization. However, NBPT+DCD was a better tool to enhance the use efficiency of both fertilizers and to reduce the N2O emission of urea fertilization. The use of manure as nitrogen fertilizer and biochar appeared to increase microbial biomass, bacteria and fungi relative abundances in the soil. In contrast, the use of NBPT+DCD presented to be detrimental to microbial biomass, especially for bacteria and saprophytic fungi. Manure fertilization and biochar application increased soil aggregation and stability. Manure application contributed to more aliphatic components (non-polar) and polysaccharides (binding agent) of soil organic matter in larger aggregates. On the other hand, biochar application increased carboxylic functional groups in smaller aggregates. Indaziflam increased CH4 emissions from a pasture soil, while nicosulfuron plus metsulfuron-methyl and oxadiazon reduced N2O emission. These findings will improve sustainable farming practices on forage production systems in southern region of United States.



Committee Chair

Wang, Jim