Morphological Development of Crested and Western Wheatgrass Following Grazing

Abstract

AbstractStage of morphological development during spring growth of perennial forage grasses can be predicted reliably from accumulated growing degree‐days (GDD) (GDID), but information is lacking on the relationship between morphological development and GDD accumulated following grazing. A study was conducted in a rainout shelter at Mandan, ND during 1987 and 1988 to determine the GDD required for morphological development of initial and regrowth forage of crested wheatgrass [Agropyron desertorum (Fisch. ex. Link) Schult.] and western wheatgrass [Pascopyrum smithii Rydb, (Löve)] Crested wheatgrass was grazed twice each year and western wheatgrass three times each year by sheep (Ovis aries L.). Water was applied weekly to provide treatments receiving 50, 100, and 150% of the long term 1 April to 1 November rainfall received at Mandan ND. Plant development following the first grazing for both species was linearly related to GDD but plant development following subsequent grazing for both species was curvilinear. The deviation from linearity became greater after the first regrowth phase for both species and occurred during periods of decreasing photoperiods. Plan development for both species was similar at all three water treatments. This information should be useful for predicting stage of plant development and, when considered with other management information, would have utility in managing grazing systems utilizing several grazing cycles.