Persistence of perennial grass crops is essential to their profitable management. Recently, orchardgrass producers in the Mid-Atlantic have reported a reduction in the persistence and regrowth vigor of their swards. The overall objective was to evaluate which factors play a major role in controlling the persistence of orchardgrass harvested for hay in the Mid-Atlantic. A survey of orchardgrass fields, growth chamber experiment, and field experiment were conducted to that end. The objectives were to: (1) assess soil fertility, management practices, disease status, and climate in relation to producer perceived stand persistence rating, orchardgrass biomass, and soil test thresholds in orchardgrass hayfields in 4 states, (2) examine the interactions of high temperature and low cutting height on the physiology and regrowth of orchardgrass in controlled environments, and (3) evaluate yield, composition, and size/density compensation-corrected productivity of orchardgrass and orchardgrass/alfalfa mixtures harvested to four cutting heights over three years. The survey of hayfields indicated that the sward age, soil organic matter, grazing, manure application, and historical average high temperature were main determinants of stand persistence score. In the growth chamber experiment, regrowth was significantly reduced by the 35°C treatment as compared to 20°C. Low cutting height significantly reduced regrowth in the cool temperature treatment, but no effect of cutting height was detected under heat stress. In the field experiment, yields were highest from plots cut to 5 cm, but orchardgrass cover in these plots thinned through the experiment. Tiller size and density measurements indicated that cutting heights of 10 cm or greater were able to achieve and maintain optimal leaf area while productivity was reduced for the 5 cm treatment. Overall, it is apparent that excessively low cutting heights are a major cause of reduced persistence in orchardgrass swards and that high temperature stress will limit regrowth. These factors likely interact with fertility and disease status, and together cause the premature loss of orchardgrass stands. Efforts should be made to communicate the importance of increased cutting height to producers. Breeding of orchardgrass resistant to fungal pathogens and heat stress may be required to sustain an orchardgrass hay industry in the Mid-Atlantic. / Ph. D.

A metabolism trial was conducted to compare the nutritional value of: 1)"Quickstand" bermudagrass [Cynodon dactylon (L.) Pers.], 2)caucasian bluestem [Bothriochloa caucasia (Trin.) C.E. Hubb], 3)tall fescue (Festuca arundinacea Schreb.), and 4)orchardgrass (Dactylis glomerata L.). The warm-season grasses (bermudagrass and bluestem) were higher (P < .01) in fiber components than the cool-season grasses (tall fescue and orchardgrass). Bluestem was lower (P < .001) in CP, hemicellulose, and ash, and higher in NDF (P < .001), ADF (P < .001), cellulose (P < .001), and lignin (P < .01) than bermudagrass. The warm-season grasses were lower in the apparent digestibility of DM (P < .001), NDF (P < .01), ADF (P < .05), cellulose (P < .05), and hemicellulose (P < .01) than cool-season grasses. Apparent digestibility of NDF (P < .001), ADF (P < .001), cellulose (P < .01), and hemicellulose (P < .01) was higher for bluestem than bermudagrass. Fescue was higher (P < .001) in apparent digestibility of DM and CP and lower (P < .01) in apparent digestibility of NDF, ADF, cellulose, and hemicellulose than orchardgrass. Lambs fed bluestem had lower (P < .05) N retention than those fed bermudagrass, when expressed as g/d. Lambs fed fescue had higher (P < .001) N retention, than those fed orchardgrass. When expressed as a percent of intake or absorption, N retention values were similar among treatments. The results of this study suggest that cool-season grasses are of higher nutritional value than warm-season grasses. / Master of Science

The effect of post-weaning supplementation of April-born Polypay and White Dorper lambs grazing alfalfa/orchardgrass pasture during two grazing seasons from June to September was studied. One hundred seventy Polypay and 133 White Dorper lambs were randomly allotted to supplemented (2% BW daily) and unsupplemented groups. It was discovered that Polypay lambs weighed more than White Dorpers at wearning, when the grazing season began, and at the end of the 80 (Year 1) and 85 (Year 2) grazing season (P < 0.01). Polypay lambs gained faster (P < 0.01) than White Dorpers. Supplemented lambs gained faster (P < 0.01) than unsupplemented and Polypays had a greater response to supplementation (P < 0.01) than White Dorpers. Polypays had higher (P < 0.01) fecal egg counts, an indicator of Haemonchus contortus infestation. Supplementation did not have any consistent effect on reducing Haemonchus contortus infestation. Differences in forage characteristics of Polypay and White Dorper lambs did appear. Differences in alfalfa and orchardgrass dry matter, neutral detergent fiber, acid detergent fiber, and crude protein availability were measured by subtracting enter from exit availabilities. The largest decrease of alfalfa components from exit to enter was found with unsupplemented Polypays. No consistent effect was found for orchardgrass components.

Cool season perennial grasses are the foundation of equine nutrition in the transition zone. The objective of this study was to evaluate forage quality using ADF, NDF, IVTDMD, CP, WSC, and ESC and changes in vegetative swards seasonally, diurnally, across species (Kentucky bluegrass, tall fescue, orchardgrass, and perennial ryegrass) and cultivar. This study was conducted in 2015 and 2017 and plots were maintained vegetatively with two to four week mowing. Morning and afternoon sample collection occurred monthly during the growing season. Samples were flash frozen; freeze dried, ground, and scanned using Near Infrared Reflectance Spectroscopy (NIRS) to predict forage quality. There was a significant year effect; therefore year was analyzed separately. Generally, ADF and NDF were highest for Kentucky bluegrass (30 and 52%), lowest for perennial ryegrass (25 and 46%), and tall fescue and orchardgrass were inconsistent. Crude protein was variable across species and season, ranging 10 to 25%. ADF and NDF concentrations were higher in the morning; IVTDMD, WSC, and ESC were higher in the afternoon; and CP was similar diurnally. In conclusion, forage quality in vegetative cool season grass pastures was sufficient to meet the nutritional needs of most equines, but varied seasonally, diurnally, across species, and cultivar.

This research examined the mechanisms by which temperature, water availability and nitrogen (N) affect the dry matter (DM) yield potential of cocksfoot (Dactylis glomerata L.) dominant pastures. The experiment was a split plot design with main plots of fully irrigated (I) or dryland (D), sub-plots of N fertiliser at 800 kg N/ha in 2003/04; and 1600 kg N/ha in 2004/05 (+N) or 0 kg N/ha (-N). The potential environmental yield of an established 8 year old cocksfoot dominant pasture was 21.9 t DM/ha/y from I+N pastures compared with 9.8 t DM/ha by I-N pastures and 15.1 t DM/ha/y by D+N pastures. The lowest yields were from dryland pastures with no N which produced 7.5 t DM/ha/y in 2003/03 and 5.0 t DM/ha/y in 2004/05. The effect of seasonal temperatures on the DM production, when periods of water stress were excluded, was quantified using thermal time accumulated above a base temperature of 3°C as 7.0 kg DM/°Cd/ha for N fertilised pastures and 3.3 kg DM/°Cd/ha for pastures with no N. The 2.5 t DM/ha difference in yields of D-N pastures in 2003/04 and 2004/05 was the result of the duration, extent and timing of the water stress period. In both years the critical limiting deficit (DL) was calculated as 78 mm from the soil moisture deficit in the 0-0.8 m soil layers. Beyond DL yield decreased at a rate of 1.45%/mm in +N and –N pastures, relative to fully irrigated control pastures. Yields of D+N and D-N pastures were similar during periods of water stress with 0.4±0.1 t/DM/ha produced during the rotation ending 30/12/2003. This was less than from either the I-N (1.2 t DM/ha) or I+N (3.5 t DM/ha) pastures due to the reduction in the amount of photosynthetically active radiation intercepted by the canopies of the dryland pastures. However, in the rotation ending 2/5/2004, after autumn rain alleviated drought conditions, yield of the D+N pasture was 2.1 t DM/ha compared with 1.7 t DM/ha by I+N pastures. The effect of N on yield was described using a nutrition index which showed that as DM yield increased N% in the herbage declined. This is a function of the ratio between metabolic and structural N requirements rather than caused by ontogeny alone. Specific leaf N was determined at two harvests and appeared constant at a given point in time (1.0-1.6 g N/m² leaf). In contrast, specific pseudostem N increased from 0.8-1.0 g N/m² pseudostem at an NNI of 0.4 in –N pastures to 2.6-3.0 g N/m² pseudostem at an NNI of 1.2 in the +N pastures. Differences between the yields of +N and –N pastures were caused by differences in radiation use efficiency (RUE) as determined by the linear relationship (R²=0.76) between RUE and the nitrogen nutrition index (NNI). In this thesis, empirical relationships for the effects of temperature, water availability and N were derived and the physiological mechanisms which underlie these descriptions were identified. These relationships provide clear and simple explanations of the effects of environmental variables on the productivity of cocksfoot based pastures which will enhance understanding of the benefits and limitations of cocksfoot, particularly in dryland farming systems.

In the semi-arid west, moisture is often the limiting factor in plant growth. High crop production is dependent upon rainfall and supplemental moisture supplied through irrigation. Plants for these areas, which are most efficient in use of water, other things being equal, would be more desirable.

The influence of agronomic practices on forage production and chemical composition of an orchardgrass-bromegrass pasture mixture was studied at the Greenville Farm, Logan, Utah, during 1960-1964. The soil is a well drained Millville Silt loam that has about a one percent slope and occurs on an alluvial fan. It is high in potash, phosphorus and calcium and is alkaline having a pH of 7.9 to 8.2. Analysis of the clipping frequency showed that the yield of forage from four harvests was greater than from five harvests. This difference was greater on plots receiving high rates of nitrogen fertilization, and frequent irrigation. Nitrogen, phosphorus, calcium, copper, iron and zinc contents were lower with five harvests. Forage production increased significantly as the available moisture in the soil increased, producing the highest yields for the 5-day irrigation interval. Nitrogen, copper, iron and zinc in the foliage decreased and phosphorus and calcium increased with increasing soil moisture. On the contrary, potassium content did not show a specific trend with increasing soil moisture. Nitrogen fertilization increased the forage dry matter production significantly giving the highest yield for 200 pounds of applied nitrogen per acre per season. The percentage of nitrogen in harvested forage decreased up to 100 pounds per acre of applied nitrogen and slightly increased with 200 pounds. Calcium, iron and manganese contents decreased and zinc content slightly increased with an increase in the amount of nitrogen fertilization. On the other hand, phosphorus, potassium and copper contents did not show a consistent trend with increasing nitrogen fertilization. A difference was noted between the amount of forage produced for different years. However, there was a tendency of decreasing forage yield with increasing age of stand. Nitrogen and phosphorus contents increased and copper, iron and manganese decreased significantly with the increasing age of stand. Potassium, calcium, and zinc contents showed a gradual decrease with the age of forage but there was a fluctuating tendency in their content for different years.

Rising fertilizer prices have led a return to the use of grass-legume mixtures to reduce N costs and improve pasture productivity. The objective of this study was to determine optimal species combinations of binary grass-legume mixtures to improve forage production and pasture nutritive value in irrigated pastures of the Intermountain West. The study was conducted at the Utah State University Intermountain Pature Research Facility near Lewiston, UT. Tall Fescue (TF), Orchardgrass (OG), and meadow brome (MB) were grown with alfalfa (ALF), birdsfoot trefoil (BFTF), and cicer milkvetch (CMV) in legume-grass mixes and monocultures at planting ratios of 25:75, 50:50, 75:25. Grass monocultures were fertilized with 0 (0 N), 67 (67 N), or 134 kg N ha-1 (134 N). Forage was harvested four times each season during 2011-2012. Forage of the mixtures and monocultures from the first and third harvests was analyzed for crude protein (CP) and neutral-detergent fiber (NDF). Average forage production of the unfertilized TF, MB, and OG monocultures was 11.03, 9.76, and 8.10 Mg ha-1, respectively. TF-ALF, OG-ALF, and MB-ALF grass-legume mixes averaged 24.0, 35.0, and 41.0% higher forage production than their respective unfertilized grass monocultures. The grass-legume mixtures with the highest CP were MB-ALF 159, TF-ALF 159, and TF-OG-159 g kg-1 and average 59, 43 and 51% higher than their respective unfertilized grass monocultures. Likewise, the mixtures with the lowest NDF were OG-ALF 453 g kg-1, OG-BFTF 469 g kg-1, and MB-ALF 480 g kg-1. These mixtures had 10, 7, and 18% lower NDF than their respective unfertilized grass monocultures. Individual harvests had similarly higher yields and CP, with lower NDF for the mixtures than the unfertilized grass monocultures. The grass-legume mixture with the 50:50 planting ratio were most productive and had high forage quality. The grass-legume mixtures had similar forage production as the grass monocultures at 134 kg N ha-1. The grass-legume mixtures also had higher CP and lower NDF than the grass monocultures. Cicer milkvetch did not perform well in irrigated pastures. Grass-legume mixtures with ALF and BFTF can be used to replace commercial N while increasing forage nutritive value.

Two studies were conducted during the grazing season of 1997. Study 1 consisted of three Experiments, and the objectives were to compare milk production and composition, body weight change and body condition score, and to determine time patterns of grazing between cows supplemented with different forms and amounts of corn. Also rumen fermentation parameters were measured in cows supplemented with two different types of corn. In study 2, milk yield was measured when grazing pasture was supplemented to lactating Holstein cows fed a typical TMR diet. Predominantly orchardgrass pastures with lesser amounts of white clover and Kentucky bluegrass were grazed during both studies. In Experiment 1, 36 Holstein cows were supplemented either with 6, 6, 6, or 4 kg/d DM of high moisture corn, coarsely ground corn, finely ground corn, or high moisture corn in two equal feedings, respectively. Milk yield was similar (30.3 kg/d) among treatments. Milk protein (2.97%) and MUN (14.7 mg/dl) did not differ among treatments. Body weight change and body condition score change were similar among treatments (23.1 kg and -0.24). During Experiment 2, four rumen-cannulated cows in mid-lactation were supplemented 6 kg/d DM of either coarsely ground corn or high moisture corn in two equal feedings. After the p.m. milking, ruminal pH was measured and rumen fluid samples were collected to determine ammonia N and VFA. While grazing, this was repeated at 0.5, 1, 2, 3,...8 h post-corn feeding (0 h). Ruminal pH was similar for both corn supplements and was lowest (5.9 and 5.8) at 5 and 8 h, respectively. Rumen ammonia N concentrations started to increase approximately 2 h after cows began grazing, reaching maximum levels 5 h later. In Experiment 3, the number of cows grazing, lying, or standing were recorded every half hour, for two consecutive days, while grazing. Cows grazed an average of 6.4 h/d, 4.1 h in the afternoon and 2.3 h in the morning. Similarity in milk production, milk composition, BW change, and BCS between treatments indicates that the quality and availability of pasture permitted equal response regardless of the type or amount of corn supplemented. Fifty four Holstein cows in mid lactation were used in Study 2. Cows were fed either a TMR diet only, or were fed TMR during half of the day (after the a.m. or p.m. milking according to the treatment) and supplemented with grazing pasture during the other half of the day. Milk production was slightly but significantly higher for cows on the TMR treatment (29.1 vs. 28.2 and 27.6). No significant difference between treatments was observed in FCM (27.7 kg/d), and milk fat (3.47) and protein percentage (3.23). While BW change did not differ among treatments (25.7 kg), body condition score increased more in cows fed only a TMR diet (0.14 vs. -0.06 and 0.01). The TMR intake was significantly different between treatments, being highest for cows on the TMR treatment and lowest for cows grazing after the p.m. milking (26.6 vs. 20.3 vs. 17.5 kg/d DM). Income over feed cost differed between treatments, and was approximately 15.3% higher for cows supplemented with high quality pasture during the afternoon compared to cows on TMR. Dairy farmers may obtain economical benefits by practicing this type of management during the grazing season with little effect on milk yield. / Master of Science

This research examined the mechanisms by which temperature, water availability and nitrogen (N) affect the dry matter (DM) yield potential of cocksfoot (Dactylis glomerata L.) dominant pastures. The experiment was a split plot design with main plots of fully irrigated (I) or dryland (D), sub-plots of N fertiliser at 800 kg N/ha in 2003/04; and 1600 kg N/ha in 2004/05 (+N) or 0 kg N/ha (-N). The potential environmental yield of an established 8 year old cocksfoot dominant pasture was 21.9 t DM/ha/y from I+N pastures compared with 9.8 t DM/ha by I-N pastures and 15.1 t DM/ha/y by D+N pastures. The lowest yields were from dryland pastures with no N which produced 7.5 t DM/ha/y in 2003/03 and 5.0 t DM/ha/y in 2004/05. The effect of seasonal temperatures on the DM production, when periods of water stress were excluded, was quantified using thermal time accumulated above a base temperature of 3°C as 7.0 kg DM/°Cd/ha for N fertilised pastures and 3.3 kg DM/°Cd/ha for pastures with no N. The 2.5 t DM/ha difference in yields of D-N pastures in 2003/04 and 2004/05 was the result of the duration, extent and timing of the water stress period. In both years the critical limiting deficit (DL) was calculated as 78 mm from the soil moisture deficit in the 0-0.8 m soil layers. Beyond DL yield decreased at a rate of 1.45%/mm in +N and –N pastures, relative to fully irrigated control pastures. Yields of D+N and D-N pastures were similar during periods of water stress with 0.4±0.1 t/DM/ha produced during the rotation ending 30/12/2003. This was less than from either the I-N (1.2 t DM/ha) or I+N (3.5 t DM/ha) pastures due to the reduction in the amount of photosynthetically active radiation intercepted by the canopies of the dryland pastures. However, in the rotation ending 2/5/2004, after autumn rain alleviated drought conditions, yield of the D+N pasture was 2.1 t DM/ha compared with 1.7 t DM/ha by I+N pastures. The effect of N on yield was described using a nutrition index which showed that as DM yield increased N% in the herbage declined. This is a function of the ratio between metabolic and structural N requirements rather than caused by ontogeny alone. Specific leaf N was determined at two harvests and appeared constant at a given point in time (1.0-1.6 g N/m² leaf). In contrast, specific pseudostem N increased from 0.8-1.0 g N/m² pseudostem at an NNI of 0.4 in –N pastures to 2.6-3.0 g N/m² pseudostem at an NNI of 1.2 in the +N pastures. Differences between the yields of +N and –N pastures were caused by differences in radiation use efficiency (RUE) as determined by the linear relationship (R²=0.76) between RUE and the nitrogen nutrition index (NNI). In this thesis, empirical relationships for the effects of temperature, water availability and N were derived and the physiological mechanisms which underlie these descriptions were identified. These relationships provide clear and simple explanations of the effects of environmental variables on the productivity of cocksfoot based pastures which will enhance understanding of the benefits and limitations of cocksfoot, particularly in dryland farming systems.