Morphological Development and Water Use in Clonal Lines of Four Forage Grasses

A need exists for information on the morphogenesis and water use by forage species to use as a basis to improve management and grazing practices, varietal improvement, and for development of plant growth simulation models. Our objectives were to evaluate morphological development and water use in clonal lines of crested wheatgrass [Agropyron desertorum (Fisch. ex Link) Schult.], western wheatgrass [Pascopyrum smithii (Rhdb.) Löve Syn: A. smithii Rydb.], intermediate wheatgrass [Elytrigia intermedia (Host) Nevsk: Syn: A. intermedium (Host) Beauv.], and reed canarygrass (Pharlaris arundinacea L.). We also defined the relationship between morphological development, water use, and air temperature expressed as growing-degree days (GDD) with a base temperature of O°C. The study was conducted during 1981 and 1982 in the field on a Parshall sandy loam soil (coarse-loamy, mixed Pachic Haploboroll) with two clones of each of two cultivars per species. Number of leaves developed in the spring and GDD per phyllochron varied among species and among clones within a species. Reproductive (spike forming) tillers of clonal lines of crested wheatgrass and western wheatgrass developed six leaves with 557 and 778 GDD, respectively; intermediate wheatgrass, seven leaves with 780 GDD; reed canarygrass, eight leaves with 706 GDD. Number of GDD required to develop a single leaf was 84 for reed canarygrass, 104 for crested wheatgrass, 125 for intermediate wheatgrass, and 147 for western wheatgrass. Western wheatgrass extracted soil water from a deeper soil depth and to a lower content than the other species. Dry matter yields were highest in intermediate wheat-grass and lowest in western wheatgrass. Water-use-efficiency (WUE) was highest in crested wheatgrass and lowest in western wheatgrass. There were no difference in total water used among clones within any species. Among the three wheatgrasses, earlier morphological development corresponded to higher WUE. Differences were observed for yield and WUE among crested and western wheatgrass clones.