Eastern Gamagrass Responds Inconsistently to Nitrogen Application in Long-Established Stands and within Diverse Ecotypes

Abstract

Eastern gamagrass (Tripsacum dactyloides) is a highly productive, highly palatable native grass tolerant to 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 have yet to be reported. The objectives were to measure the responses of long-established eastern gamagrass with different N application rates in two bottomland hay pastures and two upland grazed sites, and to measure the N responses for six diverse ecotypes in a common garden. A randomized block design was used with ecotype as the main block and fertilizer rate as the subplot. In the long-established sites, 75 N peak yields were not statistically different to those of 0 N, while upland yields across the season were consistently higher for 150 N but varied for the bottomland. The common garden ecotypes had no significant difference in yield between treatments when averaged across years. Roaring Springs showed the most consistent and greatest benefit to additional N, more than doubling the dry weight of the control. All remaining ecotypes, however, had more modest responses. Eastern gamagrass responds inconsistently to applications of 75 N, whereas most applications of 150 N generally result in higher yield, though significant increases are not guaranteed.