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Research Project: Sustainable Production and Pest Management Practices for Nursery, Greenhouse, and Protected Culture Crops

Location: Application Technology Research

Title: Container grown plants are gassy

item BROWN, FORREST - Virginia Tech
item Owen Jr, James - Jim
item NIEMIERA, ALEX - Virginia Tech

Submitted to: International Plant Propagators Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 3/13/2023
Publication Date: 7/17/2023
Citation: Brown, F.J., Owen Jr, J.S., Niemiera, A. 2023. Container grown plants are gassy. International Plant Propagators Proceedings. 72:79-86.

Interpretive Summary: Daily fertilization is essential in containerized nursery crop production. Nitrogen (N) is applied to containerized nursery crops typically as a controlled release fertilizer (CRF) formulated with a combination of ammonium (NH4), nitrate (NO3), or urea [CO(NH2)2]. Applied N remains complex and not well understood due to the numerous, and potentially concurrent, chemical and biological pathways within the growing media. This adds another layer of complexity to the question, “Where is the applied N going?” Fourier Transform Infrared Spectroscopy (FTIR) is an analytical method to determine N gas emissions in the field, ammonia and NOx simultaneously, in real-time with a ‘rugged’ instrument. Utilizing this technology, our objective was to better understand gaseous N losses from container-grown plants using two different commercially available CRF N formulations: (1) urea-ammonium-nitrate (UAN) or (2) ammonium-nitrate. There was no difference in gaseous species emitted between fertilizer treatments when individually pooled over three periods of the growing season: (early, mid, and late production), however, the sum of all N gaseous species (NOx) emitted were different between CRF treatments, UAN being the greatest. Afternoon (PM) N emissions were typically greater than morning measures. Based on this research, we estimate gasses emitted from containers from highest to lowest concentration are: N2 > NO > N2O. Further investigation into the influence of the zone of saturation within the container, irrigation regime, fertilizer placement, and substrate physical properties as factors that may influence N gaseous losses in nursery production are needed. Understanding N fate can help pave the way for a more economically efficient and environmentally friendly nursery production.

Technical Abstract: Rising mineral nutrient and polymer costs are placing a direct economic burden on nursery crop producers utilizing controlled-release fertilizer (CRF). Nitrogen (N) inputs in the containerized crop production have potential inefficiencies under a broad scope of cultural practices. While N gas emissions have been investigated in other forms of crop production, emission research on container-grown nursery production has been limited due to analytical methodology and the complexity of gaseous fate. The objective was to compare two CRFs, ammonium nitrate (AN) versus urea ammonium nitrate (UAN), to determine the gaseous emissions in the morning and afternoon using fourier transform infrared spectroscopy. These data were then used to estimate seasonal flux loss over a 53-day period. Results showed there was a higher degree of variability of gaseous flux [nitrous oxide (N2O), nitric oxide (NO), and nitrogen dioxide (NO2)] in the beginning of the season when CRFs began releasing, more consistent fluxes were exhibited during the mid to late production season. Gaseous fluxes of N species were similar regardless of CRF and time for all N species; only summation of N species ('NOx) showed statistical differences. The study of gaseous emissions in nursery production is still in its infancy and more research is necessary to gain a better understanding of gaseous flux and factors influencing flux for container-grown crops.