Variability for Ca, Mg, K, Cu, Zn, and K/(Ca + Mg) ratio among 3 wheatgrasses and sainfoin on the southern high plains

Abstract

The objective of this study was to determine the variability of Ca, Mg, K, Cu, Zn, and K/(Ca+Mg) ratio in 'Jose' tall wheatgrass [Thinopyrum ponticum (Podp.) Barkw. & D.R. Dewey], 'Luna' pubescent wheatgrass [T. intermedium subsp. barbulatum (Schur.) Barkw. & D.R. Dewey], and 'Hycrest' crested wheatgrass [Agropyron cristatum (L.) Gaertn. × A. desertorum (Fisch. ex Link.)]. Each grass was grown alone and in paired rows with 'Renumex' sainfoin (Onobrychis viciifolia Scop.) on a Pullman clay loam soil (a fine, mixed thermic Torrertic Paleustoll). Each species or mixture was evaluated under 3 cutting schedules in 1985 and 1986 and their mineral concentrations were compared to the recommended daily requirements of beef cattle. The concentration of minerals was similar in grasses grown as monocultures and in binary mixtures. The concentrations of all minerals and the ratio varied with harvest time, phenological stage, and year. Therefore, seasonal dynamics of mineral concentrations should be kept in mind when evaluating the mineral status of different forages. Among grasses, Hycrest had a better mineral profile for beef cattle than Luna or Jose. Sainfoin had higher concentrations of Ca, Mg, Cu, and Zn and much lower K/(Ca+Mg) ratio than the grasses. Hence, sainfoin-Hycrest mixtures may provide mineral concentrations more in balance with beef cattle requirements and help alleviate the problem of hypomagnesemia.