Eastern gamagrass responds inconsistently to nitrogen application in long-established stands and within diverse ecotypes

Authors: KINIRY, JAMES - Retired ARS Employee; Williams, Amber; JACOT, JACQUELINE - Oak Ridge Institute For Science And Education (ORISE); KIM, SUMIN - Dankook University; Schantz, Merilynn

Submitted to: Agronomy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/23/2024
Publication Date: 4/26/2024
Citation: Kiniry, J.R., Williams, A.S., Jacot, J., Kim, S., Schantz, M.C. 2024. Eastern gamagrass responds inconsistently to nitrogen application in long-established stands and within diverse ecotypes. Agronomy. 2024, 14, 907.
DOI: https://doi.org/10.3390/agronomy14050907

Interpretive Summary: Eastern gamagrass is a highly productive, highly palatable native grass tolerant of both drought and flooding. The objectives of this study were to measure responses of long-established eastern gamagrass with different N application rates in two bottomland hay pasture sites and two upland grazed sites; and to measure N responses for six diverse ecotypes of eastern gamagrass in a common garden. The four long-established sites 150 N treatment resulted in an increase of 49% average peak dry weight relative to zero N in 2019, and 64% in 2021. The 75 N showed an inconsistent response relative to zero N. 3 of the 4 cases were less than the zero N in 2019, and in 2021, peak yields relative to the zero N had an average increase of 41%. The ecotypes plot N response results were inconsistent among the three years. Averaging all years, 4 out of 6 ecotypes had increased yields with addition of nitrogen. Eastern gamagrass responds inconsistently to applications of 75 N, whereas most applications of 150 N saw increased yield more often than not, though significant increases are not guaranteed.

Technical Abstract: Eastern gamagrass (Tripsacum dactyloides) is a highly productive, highly palatable native grass tolerant of both drought and flooding. It has frequently shown great response to nitrogen (N) applications, but the responses of southern native ecotypes in upland and bottomland sites has yet to be reported. The objectives of this study were to measure responses of long-established eastern gamagrass with different N application rates in two bottomland hay pasture sites and two upland grazed sites; and to measure N responses for six diverse ecotypes of eastern gamagrass in a common garden. The experimental design was a randomized block design with ecotype as the main block and fertilizer rate as the subplot. For the four long-established sites, in 2019, the 150 kg N ha-1 treatment resulted in an average increase of 49% in peak dry weight relative to zero N. The 75 kg N ha-1 showed an inconsistent response in 2019 with 3 of the 4 sites being less than the zero N. In 2021, the 150 kg N ha-1and 75 kg N ha-1 treatments showed an average increase of 64% and 41% in peak yields relative to the zero N. The responses of ecotypes to 150 kg N ha-1 rate were inconsistent among the three years. The average of all years indicated an increase of biomass in 3 of the 6 ecotypes when 150 N was applied. Roaring Springs showed the most consistent and greatest benefit to additional N inputs more than doubling the dry weight of the control. However, all remaining ecotypes had more modest responses. Eastern gamagrass responds inconsistently to applications of 75 N, whereas most applications of 150 N saw increased yield more often than not, though significant increases are not guaranteed.