ARS | Publication request: Russian Wildrye Chemical Composition As Affected by Ploidy, Water and Nitrogen Levels.

Submitted to: Journal Of Range Management
Publication Acceptance Date: December 18, 2003
Publication Date: September 15, 2004
Citation: Karn, J.F., Frank, A.B., Berdahl, J.D., Poland, W.W. 2004. Russian Wildrye Chemical Composition As Affected By Ploidy, Water And Nitrogen Levels. Journal Of Range Management 57:503-510.

Interpretive Summary: Russian wildrye, is a potentially valuable cool-season bunchgrass for spring grazing, but it is currently underused. Its use has been limited by seedling establishment problems. A new tetraploid Russian wildrye has been developed which promises to have fewer establishment problems, but little is known about its nutritive quality. Before tetraploid plants are widely recommended to producers it is important to learn more about their spring quality. A study was undertaken to determine the affect of growing season water (50 and 150% of average), and nitrogen (N) fertilizer (10 and 134 kg N/ha), on the nutritive quality of diploid and tetraploid Russian wildrye plants harvested at 4 stages of maturity over 3 years. Diploid plants had slightly (P<0.05) more crude protein (CP) in leaf, stem and head tissue than tetraploid plants. Plants grown at the 50% water treatment had higher CP and in vitro true digestibility (IVTD), and lower acid detergent fiber (ADF) and neutral detergent fiber (NDF) in leaf and head tissue. In stem tissue only CP was affected by growing season water. Nitrogen fertilizer resulted in greater CP and IVTD and lower ADF and NDF in all 3 plant tissues. Maturity affects were consistent over leaf, stem and head tissue, with CP and IVTD declining and ADF and NDF increasing as plants matured. Nutritive quality differences between current Russian wildrye varieties (diploid) and the newer tetraploid plants were small, indicating the newer material still has good nutritive quality and it is more easily established. Generally drought stress (50% of average water) increased forage quality.

Technical Abstract: Russian wildrye [Psathyrostachys juncea (Fisch.) Nevski], a cool-season introduced bunchgrass, offers producers an alternative to crested wheatgrass [Agropyron desertotum (Fisch. Ex Link) Schultes] for spring and fall grazing in the Northern Great Plains. Tetraploid Russian wildrye with improved seedling establishment may offer even greater potential for seasonal grazing. This study investigates how the concentrations of some nutritive quality components in leaf, stem, and head tissue of diploid and tetraploid Russian wildrye were affected by growing season water treatment (50 and 150% of average precipitation) and fertilizer (10 and 134 kg N ha-1). Plants were sampled at vegetative, boot, anthesis, and anthesis plus 10-d stages of maturity in 1994, 1995, and 1996. Tetraploid plants had slightly (P<0.05) less crude protein (CP) in leaf, stem and head tissue than diploid plants. Plants grown at the 50% water treatment had higher CP and in vitro true digestibility (IVTD), and lower acid detergent fiber (ADF) and neutral detergent fiber (NDF) in leaf and head tissue, while in stem tissue only CP was affected by the growing season water treatment. Nitrogen fertilizer resulted in greater CP and IVTD and lower ADF and NDF in all 3 plant tissues. Maturity affects were consistent over leaf, stem and head tissue, with CP and IVTD declining and ADF and NDF increasing as plants matured. Crude protein at all stages of maturity in leaf and head tissue would have been adequate for most classes of beef cattle, while stem tissue CP would have only been adequate for lower producing animals.