Location: Soil Dynamics Research2010 Annual Report
1a. Objectives (from AD-416)
Objectives include: (1) determine what carbon sequestration potentials exist within nursery systems; (2) develop strategies for increasing carbon sequestration above current levels; 3) measure greenhouse gas emissions from nursery production systems; and (4) develop practices to reduce greenhouse gas emissions from nursery production systems.
1b. Approach (from AD-416)
Measurement of potential C sequestration will be accomplished by making soil and gas sampling measurements in an existing alternative substrate study. Auburn University Horticulture Department has an ongoing effort to develop alternative substrates for horticultural production. Within this study, C sequestration levels will be monitored and compared to soil conditions which have not been disturbed by planting. In a second study, three pot sizes commonly used in the nursery industry (trade gallon, gallon, and 3 gallon) will be examined. Greenhouse gas emissions will be measured weekly from these pots over the course of the growing season.
3. Progress Report
Auburn University, in cooperation with USDA-ARS, is conducting a joint test to develop strategies for increasing carbon sequestration and to measure greenhouse gas emissions within nursery systems. The contribution of the horticultural industry to the rising level of carbon dioxide (and other trace gases) in the atmosphere is unknown. This work is being conducted at the Horticulture Research Facilities at Auburn University. In the trace gas study, dwarf yaupon holly is being grown in four commonly used container sizes (trade gallon, gallon; two gallon, three gallon) using standard production potting media and growing practices. Trace gas emissions are assessed weekly from seven containers of each size with plants and three containers of each size without plants. Gas samples are collected in situ using the static closed chamber method according to USDA’s Greenhouse Gas Reduction Through Agricultural Carbon Enhancement network (GRACEnet) protocols. Gas samples for carbon dioxide, methane, and nitrous oxide are taken at 0, 15, 30, and 45 min intervals following chamber closure to calculate gas flux rates and analyzed using gas chromatography. In the carbon sequestration study, plants were grown in containers using three differing substrates (pine bark, clean chip residual, and whole tree) for one season prior to outplanting to the field. Soil samples were collected in Summer, 2009 for determination of soil C and N at which time Automated Carbon Efflux Systems (ACES) were installed adjacent to three plant species (crape myrtle, magnolia, and Shumard oak) to monitor (24 hr d-1) C lost through soil respiration. Biomass has been and will continue to be assessed to determine the amount of C in plant material. Having information on both inputs (biomass) and outputs (respiration) will allow for determination of C sequestration potential in these potting media/plant species systems. Trace gas samples continue to be analyzed via gas chromatography and data prepared for statistical analysis. In the carbon sequestration study, crape myrtle had higher soil carbon dioxide efflux than magnolia, possibly due to a larger root system or faster growth rate. Pine bark had lower soil efflux than clean chip residual in crape myrtle, while in magnolia this relationship was reversed. However, whole tree had significantly lower soil flux than either pine bark or clean chip residual. Whole tree has a higher percentage of wood than either pine bark or clean chip residual which may cause it to break down slower, resulting in lower soil flux. With crape myrtle, all three media had significantly different soil flux values; there was no effect of media for magnolia. Soil flux data for Shumard oak are currently being analyzed. Our results indicate that C storage potential may increase with utilization of whole tree as a growing media for container crops. Additional data such as plant biomass increase and changes in soil C levels over time will also be needed to fully understand the impact of these growing media on soil carbon dioxide emission. The ADODR has monitored activities via email and telephone correspondence, collaborator meetings, and site visits.