Contrasting rhizosphere nitrogen dynamics in Andropogoneae grasses

Authors: HSU, SHENG-KAI - Cornell University; Emmett, Bryan; HAAFKE, ALEXANDRIA - Orise Fellow; COSTA-NETO, GERMANO - Cornell University; SCHULZ, AIMEE - Cornell University; Lepak, Nicholas; LA, THUY - Cornell University; AUBUCHON-ELDER, TAYLOR - Donald Danforth Plant Science Center; HALE, CHARLES - Cornell University; RAGLIN, SIERRA - University Of Illinois; OJEDA-RIVERA, JONATHON - Cornell University; KENT, ANGELA - University Of Illinois; KELLOG, ELIZABETH - Donald Danforth Plant Science Center; ROMAY, CINTA - Cornell University; Buckler Iv, Edward

Submitted to: The Plant Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/23/2025
Publication Date: 7/5/2025
Citation: Hsu, S., Emmett, B.D., Haafke, A.J., Costa-Neto, G., Schulz, A.J., Lepak, N.K., La, T., Aubuchon-Elder, T.M., Hale, C.O., Raglin, S.S., Ojeda-Rivera, J., Kent, A.D., Kellog, E.A., Romay, C.M., Buckler Iv, E.S. 2025. Contrasting rhizosphere nitrogen dynamics in andropogoneae grasses. The Plant Journal. https://doi.org/10.1111/tpj.70319.
DOI: https://doi.org/10.1111/tpj.70319

Interpretive Summary: Application of nitrogen (N) fertilizer in agricultural systems can contribute to environmental pollution in waterways and the production of nitrous oxide, an important greenhouse gas. Thus, keeping N in the field for plant use is important for both agricultural productivity and environmental concerns. Plants interact with soil microorganisms to influence N cycling in multiple ways that can either increase N losses or conserve N in the soil. Nitrification, which converts ammonium to nitrate is a critical step in the N cycle. Ammonium is relatively stable in soil, while nitrate is mobile. Therefore, nitrification can lead to N losses. It is believed that plants that slow the nitrification process can help keep N in agricultural fields. In this work, researchers tested whether grass species closely related to corn could decrease nitrification and retain N in soil. Contrary to expectations, short-lived annuals such as corn and sorghum slowed nitrification. While longer-lived perennial species tended to increase nitrification rates. Several plant genes involved in taking up nutrients from soil and in the production of plant compounds known to inhibit nitrification were strongly related to variation in N cycling observed among the plant species. This information will help plant breeders and geneticists to develop corn varieties that maximize nitrogen retention and increase the efficiency of N use in agricultural systems. The work will be of value to researchers of soil N and land managers who desire better nitrogen management.

Technical Abstract: Background: Nitrogen (N) fertilization in crop production significantly impacts ecosystems, often disrupting natural plant-microbe-soil interactions and causing environmental pollution. Our research tested the hypothesis that phylogenetically related perennial grasses might preserve rhizosphere management strategies conducive to a sustainable N economy for crops. Methods: We analyzed the N cycle in the rhizospheres of 36 Andropogoneae grass species related to maize and sorghum, investigating their impacts on N availability and losses. This assay is supplemented with the collection and comparison of native habitat environment data for ecological inference as well as cross-species genomic and transcriptomic association analyses for candidate gene discovery. Results: Contrary to our hypothesis, all examined annual species, including sorghum and maize, functioned as N "Conservationists," reducing soil nitrification potential and conserving N. In contrast, some perennial species enhanced nitrification and leaching ("Leachers"). Yet a few other species exhibited similar nitrification stimulation effects but limited NO3- losses ("Nitrate Keepers"). We identified significant soil characteristics as influential factors in the eco-evolutionary dynamics of plant rhizospheres, and highlighted the crucial roles of a few transporter genes in soil N management and utilization. Conclusion: These findings serve as valuable guidelines for future breeding efforts for global sustainability.