Forage Yield and Quality of Warm- and Cool-Season Grasses

Abstract

High quality forage is needed in the northern Great Plains during the summer when major growth of cool-season grasses has ceased and quality of standing forage is low. The objective of this study was to compare forage yield, nutritional quality, and water use of 2 warm-season grasses {P-15584 little bluestem [Schizachyrium scoparium (Michx.) Nash] and 'Pierre' sideoats grama [Bouteloua curtipendula (Michx.) Torr.]} and 2 cool-season grasses {'Nordan' crested wheatgrass [Agropyron desertorum (Fisch. ex Link) Schult.] and 'Mayak' Russian wildrye [Psathyrostachys juncea (Fisch.) Nevski]} harvested from 1979 through 1982 at anthesis or when drought stopped further plant growth. Forage was harvested from established stands seeded in rows 53-cm apart growing on a silty range site (Typic Haploborolls) near Sidney, Mont. Plots were 8 by 23 m replicated 5 times in randomized complete blocks. Forage yield averaged 0.84, 0.98, 1.75, and 2.52 t/ha (S-mean=0.17); in vitro organic matter digestibility averaged 56.4, 67.3, 62.0, and 62.3% (S-mean=1.1)$, crude protein averaged 8.0, 10.3 8.6, and 12.8% (S-mean=0.4); phosphorus averaged 0.14, 0.16, 0.15, and 0.16% (S-mean=0.01) over a 4-year period for little bluestem, sideoats grama, crested wheatgrass, and Russian wildrye, respectively. Regression showed that in vitro organic matter digestibility and crude protein concentration were negatively correlated with forage yield. Forage yield and phosphorus concentration were positively correlated with evapotranspiration. The study showed that Russian wildrye would provide the highest quality forage during June and sideoats grama during July. Livestock need both cool- and warm-season forages to provide the highest forage quality.