Date of Graduation
Davis College of Agriculture, Natural Resources and Design
Agroecosystems occupy a large portion of the United States and receive a disproportionally high amount of terrestrial nitrogen inputs. As application rates increase, nitrogen use efficiency declines leading to higher rates of nitrogen loss. To develop sustainable agricultural practices, the long-term effects of management practices on the soil microorganisms that perform central roles in the transformation of nitrogen need to be studied. To study the long-term impacts of compost application and pasture integration in crop rotation, samples were collected from the existing 19-year-old Organic Crop Livestock Field (OCLF) experiment on the WVU organic research farm. The OCLF experiment includes a crop rotation treatment with a pasture period, a compost amendment treatment, and the combination of the two on a four-year crop rotation. The compost-input and pasture integrated rotation treatments increased soil organic matter, respiration, and extracellular enzyme activity, suggesting enhanced soil microbial activity.
Soil prokaryotic community composition was affected by the long-term treatments, including compost driven increases in the abundance of ammonia oxidizing organisms (AOO), rapid ammonification, higher rates of potential nitrification, and higher concentrations of nitrate early in the season, but these effects were all greatly mitigated by the pasture integration. The rate of nitrification was correlated with the abundance of AOO, indicating the importance of this group of organisms to the nitrogen cycle and highlights the connection between nitrification, ammonium availability, and community composition and function. As crop yields were unaffected by pasture integration, this management practice could reduce the potential for nitrogen loss without reducing productivity.
Walkup, Jeth GV, "Crop rotations that integrate pasture are less vulnerable to nitrogen leaching due to changes in microbial community composition and reduced nitrification" (2018). Graduate Theses, Dissertations, and Problem Reports. 3696.