Native grasslands are a sink for atmospheric CO2 sequestration, but ways for extending site-specific CO2 flux measurements to a regional scale are lacking. Objectives of this study were to determine the utility of using canopy radiometric reflectance for estimating CO2 fluxes for semiarid grasslands. The relationship between the normalized difference vegetation index (NDVI) calculated from spectral reflectance data obtained with hand-held radiometers was compared to CO2 flux calculated from Bowen ratio/energy balance measurements. Carbon dioxide flux was measured during the plant growing season over a nongrazed prairie, grazed prairie, and a shrub dominated prairie site near Mandan, N.D. Measurements were also made of evapotranspiration (ET), green biomass, and green leaf area index (LA!). Correlation coefficients of NDVI with vegetation parameters of biomass and LAI for each site and year exceeded 0.84

High quality forage for spring and autumn grazing can be obtained from Russian wildrye [Psathyrostachys juncea (Fisch.) Nevski], a cool-season bunchgrass. However, little is known about mineral concentrations critical to livestock production, especially in the relatively new tetraploid plants. A knowledge of plant mineral concentrations and how they can be manipulated to more nearly meet animal requirements is necessary to optimize animal production. A study was undertaken to determine the extent that concentrations of critical minerals in leaf and stem tissue of Russian wildrye were affected by ploidy level, growing-season water (50 and 150% of average), and N fertilizer (10 and 134 kg N ha 1). Plants were sampled at vegetative, boot, anthesis, and anthesis plus 10-day stages of maturity in 1994, 1995, and 1996. Ploidy level resulted in small but significant differences in some mineral concentrations, with diploid plants usually having higher levels. An exception was P in stem tissue. This finding indicates that in breeding and selection for other traits, forage quality was not adversely affected. Growing-season water level also had minimal effects on mineral concentrations, except for P which was enhanced (P < 0.05) by greater amounts of soil water. Fertilizer N increased forage levels of Ca, K, Cu, and Zn, and decreased levels of P. Higher concentrations of K are not desirable, because they increase the possibility of a grass tetany problem. Advancing plant maturity caused a decrease in P and Zn concentrations, but Ca and Mg in leaf tissue increased as plants matured. These results suggest that concentrations of P, Ca, Mg, and Cu were marginal for high producing cattle at some stages of maturity, but we found the effects of nitrogen and growing-season water did not result in leaf and stem mineral concentration changes that would adversely affect the safety and nutritive quality of Russian wildrye.

Russian wildrye [Psathyrostachys juncea (Fisch.) Nevski], a cool-season introduced bunchgrass, offers producers an alternative to crested wheatgrass [Agropyron desertorum (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 inflorescence tissue of diploid and tetraploid Russian wildrye were affected by growing season water (50 and 150% of average precipitation) and fertilizer (10 and 134 kg N ha-'). Plants were sampled at vegetative, boot, anthesis, and anthesis plus 10-day stages of maturity in 1994, 1995, and 1996. Tetraploid plants had slightly (P < 0.05) less crude protein (CP) in leaf, stem and inflorescence tissue than diploid plants. Plants grown at the 50% water treatment had higher CP and in vitro dry matter digestibility (IVDMD), and lower acid detergent fiber (ADF) and neutral detergent fiber (NDF) in leaf and inflorescence tissue, while in stem tissue only CP was affected by the growing season water treatment. Nitrogen fertilizer resulted in greater CP and IVDMD and lower ADF and NDF in all 3 plant tissues. Maturity affects were consistent over leaf, stem and inflorescence tissue, with CP and IVDMD declining and ADF and NDF increasing as plants matured. There were some differences in nutritive quality components between diploid and tetraploid plants, but overall their qualities were comparable and quite good. Crude protein at all stages of maturity in leaf and inflorescence tissue would have been adequate for most classes of beef cattle, while stem tissue CP would have only been adequate for lower producing animals.

Russian wildrye [Psathyrostachys juncea (Fisch.) Nevski], a cool-season introduced bunchgrass, offers producers an alternative to crested wheatgrass [Agropyron desertorum (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 inflorescence tissue of diploid and tetraploid Russian wildrye were affected by growing season water (50 and 150% of average precipitation) and fertilizer (10 and 134 kg N ha-'). Plants were sampled at vegetative, boot, anthesis, and anthesis plus 10-day stages of maturity in 1994, 1995, and 1996. Tetraploid plants had slightly (P < 0.05) less crude protein (CP) in leaf, stem and inflorescence tissue than diploid plants. Plants grown at the 50% water treatment had higher CP and in vitro dry matter digestibility (IVDMD), and lower acid detergent fiber (ADF) and neutral detergent fiber (NDF) in leaf and inflorescence tissue, while in stem tissue only CP was affected by the growing season water treatment. Nitrogen fertilizer resulted in greater CP and IVDMD and lower ADF and NDF in all 3 plant tissues. Maturity affects were consistent over leaf, stem and inflorescence tissue, with CP and IVDMD declining and ADF and NDF increasing as plants matured. There were some differences in nutritive quality components between diploid and tetraploid plants, but overall their qualities were comparable and quite good. Crude protein at all stages of maturity in leaf and inflorescence tissue would have been adequate for most classes of beef cattle, while stem tissue CP would have only been adequate for lower producing animals.