Alfalfa is difficult to ensile because of its low water soluble carbohydrate content, low dry matter content, and high buffering capacity. Therefore, the isolation of mutants of L. plantarum was undertaken to develop a strain(s) which could improve the fermentation of alfalfa silage when used as an inoculum. Efforts to isolate starch- or hemicellulose-utilizing strains proved unsuccessful as did the isolation of high temperature resistant mutants and oxygen resistant mutants. Mutants resistant to plumbagin (an intracellular O₂- generator) and citrate were isolated. Of these mutants, some were found to be more sensitive to cadmium than the parent strain. Though these three characteristics point to an enhanced manganese accumulation since O₂- is scavenged by manganese, citrate will chelate manganese, making it unavailable to the organism, and cadmium is transported by the manganese transport system, the rates of 54_Mn transport were no greater than the parent. When grown aerobically on a glucose-limited medium, the parent strain consumed oxygen and produced high concentrations of acetic acid and low concentrations of lactic acid. By contrast, one mutant (strain MC226), produced high concentrations of lactic acid and demonstrated low rates of O₂ consumption and low levels of acetic acid. The parent strain and two plumbagin- and citrate-resistant mutants were used to inoculate alfalfa for silage production. The inoculated silages showed a lower pH and higher titratable acidity than that of an uninoculated control. Silages inoculated with the parent strain exhibited high levels of acetic acid and low levels of lactic acid, indicative of oxygen consumption by the parent strain. Less acetic acid was evident in silages inoculated with the mutant strains. All silages contained a high level of butyric and isobutyric acids and propionic and isovaleric acids were also detected, indicative of clostridial growth. / Master of Science

The conclusion of the alfalfa fertility investigations at Glade Spring and at Culpeper may be summarized as follows; 1. Potassium was the main limiting factor in the growth, duration of stand, vigor, and color of alfalfa. 2. In general, yields were related directly to rate of potash fertilization. 3. Yield variations due to phosphorus fertilization were insignificant. 4. Sodium gave increased yields at Glade Spring and Location A at Culpeper, but had little or no effect on yields at Culpeper at Location B. 5. In general, yields were decreased by the application of minor elements. 6. In 1950 and 1951 at Glade Spring, more potassium was removed from the soil than was applied, the deficits ranging from only 8.4 pounds per acre of potassium where a 2-24-24 fertilizer was used, to 68.9 pounds per acre of potassium where e 2-12-0 fertilizer was used. 7. The potassium removed per ton of hay was closely correlated with the rate of potassium fertilization. 8. The phosphorus removed in the hay varied from 1/2 to 1/8 of the phosphorus applied in the fertilizer. 9. The phosphorus removed was nearly constant regardless of the rates of phosphorus fertilization. 10. Potassium decreased sodium uptake in the alfalfa; on the other hand, sodium had no effect on potassium uptake. 11. Alfalfa appears to be a sodium accumulating plant when sodium is used as a supplement with potassium. 12. Potassium depressed the absorption of calcium, magnesium, and sodium. 13. At Glade Spring, potassium slightly depressed phosphorus absorption but had no noticeable effect on phosphorus uptake at Culpeper. Potassium appeared to have no appreciable effect on nitrogen content. 14. The soil at Glade Spring had approximately 30 times as much exchangeable calcium as potassium. As a result, the calcium content of the alfalfa was often higher than the potassium content. 15. Available phosphorus in the topsoil at Glade Spring was about five times higher than in the subsoil; on the other hand, available phosphorus at Culpeper was about equal in topsoil and subsoil. / Master of Science

Laboratory studies and field observations were conducted to ascertain the development of the female sex organs of the alfalfa weevil during aestivation, to study the role of this aestivation on sexual development, and to investigate the factors responsible for this interaction. Measurements of female sex organs were made in dissected weevils at monthly intervals to observe each of the developmental stages of sexual maturation. Results of this sexual development as it progressed after adult emergence, were presented by means of tables, graphs, and a series of photographs. The importance of not confusing old and new weevils was recognized in this work, since their behavioral patters differ in many respects. The nature and physiology of the aestivation of this weevil was discussed and evidence was presented to support the author's suggestion that this aestivation is a "true diapause." It was demonstrated in this paper that diapause synchronized the sexual growth of the alfalfa weevil to the seasonal changes of the year for species adaptation and survival. / Master of Science

For Virginia, the primary forage base is endophyte-infected tall fescue (Schedonorus phoenix (Scop.) Holub). However, the decreased animal performance and disorders caused by the presence of the fungal endophyte Neotyphodium coenophialum reduces its suitability for many forage-livestock producers. The endophyte, which is found in the inter-cellular space of tall fescue tissues, forms a mutalistic relationship with the plant and helps the fescue tolerate drought, insect predation, and grazing pressure. The production of toxic ergot alkaloids by the endophyte is associated with decreased performance of animals that graze endophyte infected tall fescue. The objective of the current experiment was to determine how tall fescue type (endophyte free vs novel endophyte) and orchardgrass-legume (alfalfa vs clover) mixture affect grazing behavior of weaned steers. Forty-eight weaned steers (218 ± 18 kg) were blocked by frame score (medium and large), and randomly assigned within block to four treatments with three replications in a 2x2 factorial design. Each treatment consisted of 2 paddocks with the combination of tall fescue and legume-orchardgrass mixture as follow: alfalfa-orchardgrass mixture (A)/E-, clover-orchardgrass mixture (C)/E- , A/E++ and C/E++. Each group of 4 steers had 24 h access to both tall fescue stand and legume-orchardgrass mixture. Botanical composition of paddocks was determined on d 0, and forage mass, sward height and nutritive value were determined on d 0, 17 and 33. Behavior of steers was scanned every 5 min on d 24 and 25 from 0700 to 1900. The proportion of legumes was higher (P = 0.001) in A paddocks(37 %) compared to C paddocks (6%), while the percent orchardgrass was lower (P = 0.040) in A (33 %) than C (53 %). The proportion of broadleaf and grassy weeds was higher (P = 0.013) in E- paddocks (11 %) as compared with E++ paddocks (3 %). Sward height and herbage mass were similar between treatments during the experiment (P > 0.05). Nutritive value (CP, NDF and ADF) did not differ between fescue paddocks (P > 0.05). However, within mixed swards, CP was higher and NDF was lower in A compared with C (P < 0.05). Acid detergent fiber was (P < 0.05) lower in A than C only on d 0 and 17. Average daily gain did not differ between treatments (P > 0.05). Steers spent higher (P = 0.002) proportion of the daylight time grazing in treatments with C (56 %) as compared with A (50 %), and in treatments (P = 0.023) with E++ (55 %) compared with E- (52 %). Time spent ruminating, idling and lying, as well as steps taken per day, did not differ between treatments (P > 0.05). Regardless of differences in weeds between E- and E++, these results indicate that fescue type affected grazing behavior of calves. Difference between mixed swards in proportion of ground cover with legumes and orchardgrass, as differences in nutritive value between A and C may have affected grazing behavior of calves between mixed swards, instead of a legume species effect within mixtures. / Master of Science

A controlled feeding experiment was conducted to compare the influence of barn-cured and field-cured alfalfa hay out from the same field on milk production and liveweight of dairy cows. Twelve Holstein cows were used in this trial. The double-reversal feeding method was followed. Grain was fed at the same rate to each group of cows. Hay was fed as the only source of roughage, and equal amounts of the two kinds of hay were fed to the two groups of cows. There was practically no difference in the total consumption of the two kinds of hay. Analysis of variance on the amounts of four per cent fat-corrected milk produced revealed highly significant differences at the one per cent level in favor of the barn-cured hay. The hays were sampled at regular intervals for proximate analysis. At the time of feeding the barn-cured hay contained .36 per cent more moisture, 2.63 per cent more protein, .26 per cent more fat, 1.20 per cent less fiber, 2.26 per cent less nitrogen-free extract, and .66 per cent more ash. The cows gained slightly in liveweight when they received the field-cured hay and lost slightly in liveweight when they received the barn-cured hay. Liveweight changes were not significant when analyzed statistically. / Master of Science

The qualitative and quantitative aspects of mating behavior, the stimulus for locating and mating, and the effects of varying temperatures on mating behavior and oviposition were studied in the laboratory. Postdiapausing weevils, collected in April, and nondiapausing weevils, reared in the laboratory, were utilized. In both groups, the males aggressively mounted the females from any angle or position with little or no indication of prior courtship. In petri dishes at 75 ± 3° F, both groups spent about 59% of their total time in mating behavior. Mounted time spent in actual copulation (aedeagus inserted) was 47% for nondiapausing pairs and 74% for postdiapausing pairs. This difference in behavior was probably caused by the younger, nondiapausing females which often prevented copulation by tucking the genital opening under the elytra. Males, when given a choice between virgin and non-virgin females, mated with non~virgins in a ratio of 7:1. Nondiapausing pairs mounted fewer times .for longer durations per mounting than the postdiapausing. Crowding by other weevils appeared to reduce mating efficiency, but not mating initiation. Sight was found to play a role in attracting weevils to each other over distances of.a few inches. No evidence of sound production was discovered, nor was there found to be a pheromone serving as a sex attractant. Since males mounted other males as well as other species of curculionids, there is apparently rto mechanism for recognition of sex or species. Higher temperatures resulted in a greater number of mountings of shorter duration. At lower temperatures, pairs mounted fewer times and riot infrequently copulated for as long as 12 hours. The number of ovipositing females and the average number of eggs per female increased with the temperature. / Master of Science

M.S.

Alfalfa (Medicago sativa L.) harvest schedules are often interrupted by rainfall, unfavorable environmental conditions for growth, and unfavorable weather for hay curing. Interruptions in alfalfa harvest schedules can delay the final harvest until dates considered critical to winter survival. Harvests made between 20 September and 30 October are considered detrimental to the persistence of alfalfa stands in geographical areas such as western Virginia. The objectives of this study were to determine if a critical period for fall harvest management actually exists in Virginia, if length of the growth period prior to fall harvest (GPPFH) influences plant persistence and succeeding spring yields, and if photosynthesis offsets respiration and allows more flexible fall harvest management than is currently recommended. Final alfalfa harvests were made 10, 20, or 30 September or 10, 20, or 30 October for 2 years in two identical experiments. Alfalfa was managed to achieve 30, 40, 50, or 60 days of growth prior to each fall harvest date. Total nonstructural carbohydrates (TNC) in tap roots and population of surviving plants were determined in December and March. Succeeding spring yields were measured in May. Zero, 45, and 60 percent shade were imposed following four fall harvest dates in a supplemental study to investigate the influence of photosynthesis on TNC levels and plant persistence. In the supplemental study, CO₂ exchange and TNC were measured at 2 week intervals in the fall following four fall harvest dates. Harvests made during the fall period previously considered as critical did not cause over-wintering plant losses. Length of growth period prior to fall harvests was more important than date of fall harvest in making management decisions for fall harvest. Although spring yield generally increased with length of GPPFH, the spring growth appeared healthy; so one might expect a few days of delay prior to the first spring harvest to eliminate any detrimental influence of short length of GPPFH. Succeeding spring yields and TNC levels were generally high for the 50-day GPPFH, and fall harvest yield offset any reductions in spring yield observed in this study. In addition, fall harvests made with a 50-day GPPFH maintained quality and leafiness as opposed to a 60-day GPPFH. Fall regrowth and plant maintenance were not dependent on root TNC accumulation. Photosynthesis offset TNC losses for regrowth and maintenance during the fall. High photosynthetic rates as compared to respiration occurred because temperatures were within the optimum range for photosynthesis of alfalfa during 68% of the daylight hours from September through November. There was no critical period for fall harvest management with the environmental conditions experienced during this study. A 50 or 60-day GPPFH prior to fall harvest was adequate for plant persistence and high succeeding spring yields. / Ph. D.

No description available.

3 pp. / Revised / The most effective weed control practice in alfalfa is maintaining a healthy crop and dense stand. Cultural practices that promote a vigorous stand can reduce the need for chemical weed control. Cultural practices that promote a healthy stand reduce the need for chemical weed control, but herbicides are sometimes necessary even in well-managed alfalfa.