Agronomic characteristics and nutritive value of 11 grasses grown with irrigation on a saline soil in southwestern Saskatchewan

Abstract

Agronomic and nutritive characteristics of 11 grasses were studied at Swift Current, Saskatchewan on a moderately saline irrigated soil: [smooth bromegrass (Bromus inermis Leyss.), meadow bromegrass (Bromus riparius Rehmann), tall wheatgrass (Elytrigia elongata (Host) Nevski), crested wheatgrass (Agropyron desertorum (Fisch. ex Link) Schult.), intermediate wheatgrass (Elytrigia intermedia (Host) Nevski), slender wheatgrass (Elymus trachycaulus (Linke) Gould ex Shinners), Altai wild ryegrass (Leymus angustus (Trin. Pilger), Russian wild ryegrass (Psathyrostachys junceus (Fisch.) Nevski), Dahurian wild ryegrass (Elymus dahuricus Turcz ex Grieseb), reed canarygrass (Phalaris arudinaceae L.) and creeping foxtail (Alopecurus arundinaceus Poir.)]. Grasses were clipped at three-leaf, heading and seed set. Yield, leaf-to-stem ratio (LSR), botanical composition (BC), crude protein (CP), phosphorus, fibre and in vitro dry matter digestibility (IVDMD) were determined. There were differences (P < 0.05) between the grasses in yield at each growth stage with smooth bromegrass and creeping foxtail having high yields and meadow bromegrass low yields at all growth stages. The BC of most target grasses was greater than 60%. Exceptions were Dahurian wild ryegrass, crested wheatgrass, tall wheatgrass and meadow bromegrass. There were few significant differences between the grasses for LSR, except that Russian and Altai wild ryegrasses and meadow bromegrass had higher LSR (P < 0.05) than the other grasses. Differences in CP, P, neutral (NDF) and acid (ADF) detergent fibres were inconsistent and small at each growth stage but CP and P declined (P < 0.05) while NDF and ADF increased (P < 0.05) with plant maturation. There were differences (P < 0.05) between years and cuts for all traits except between years for yield, BC and LSR at seed set (P > 0.05). Dry matter intake (DMI) NDF and in vivo dry matter digestibility (DMD) were determined for hay cut from each plot using sheep. The relationship between forage NDF and DMI: DMIg kg BW-1d-1 = 86.5 - 0.09 NDF (r2 = 0.87; RSD = 1.16; P < 0.001)] was used to calculate predicted DMI (PDMI) for all clipped samples. Hay IVDMD differed from DMD (P < 0.05) and the regression DMD = 1.27 IVDMD - 5.75 (r2 = 0.89; RSD = 3.21; P < 0.001) was used to adjust IVDMD to predicted in vivo digestibility estimates (PDMD). PDMD differed (P < 0.05) between the grasses only at heading and seed set. Yield of PDDM (YPDDM), yield of CP (YCP) and the sum of these and PDMI were used to rank the grasses for usefulness as hay or pasture for early or late grazing.