Edaphic Requirements and Characteristics of Purpletop 1

Cool‐season forage species are of major importance to the livestock industry in the northeastern part of the United States. Growth of these species is characterized by periods of high production followed by periods of low production. Purpletop [ Tridens flavus (L.) Hitchc.], a warm‐season grass species, makes its major growth during the summer months when cool‐season species are unproductive. It may have potential for reducing seasonal variations in forage production when grown in association with cool‐season species. In order to evaluate purpletop for forage purposes, more information is needed on its soil requirements and agronomic characteristics. In this investigation nine indigenous purpletop stands were studied relative to edaphic factors, management, and plant characteristics associated with the stands. A stepwise regression procedure was used to determine soil properties associated with the occurrence of purpletop. The sand fraction in the top 15 cm of the soil profile, as determined by a hydrometer method, was more closely associated with the occurrence of purpletop than any other factor studied. Soil pH, available P, K, Ca, and cation exchange capacity influenced the presence of purpletop in a complex interrelationship. Purpletop was found growing under different pH's, fertilities, and grazing systems, although none of the swards was under intensive management. Number of leaves (5.7), plant height (114 cm), panicle length (29.2 cm), blade length (40.8 cm), and blade width (12.7 mm) did not vary among sites, suggesting little genetic variation among indigenous populations of purpletop in West Virginia. Forage concentrations of P (0.21%), K (1.44%), Ca (0.22%), and Mg (0.14%) varied among sites but were related to soil levels of these minerals. No obvious problems were found that would suggest poor forage potential. Further investigations are needed to determine its place as a forage in livestock programs.