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Spray‐irrigating grass swards with food‐processing effluent on the Delmarva Peninsula creates the problem of grass accumulation. We hypothesized that spray‐irrigated grass would support a relatively high stocking rate of grazing cattle, and that the effluent would be a source of fertilizer nutrients and digestible energy for livestock. Four mixed orchardgrass (Dactylis glomerataL.) and tall fescue (Festuca arundinaceaSchreb.) paddocks, each 0.202 ha, were rotationally grazed at monthly intervals summer and autumn for 2 years with steers or heifers, averaging about 300 kg. The cattle were fed ground corn (Zea maysL.) at 1% body weight/day. Small amounts of commercial fertilizer were needed periodically to stimulate plant growth. Enough aftermath grass was produced to support 7.4 head/ha in summer and autumn without loss of stand. Forage quality (crude protein, energy, and mineral content) was good throughout the grazing season, but better in autumn than in summer. Energy levels in autumn approached that of concentrates. With the exception of Ca content prior to application of gypsum, mineral element composition of grass in effluent‐irrigated pastures was much superior with regard to animal nutrition than that of untreated controls as well as grass grown elsewhere in the Northeast. Steers gained an average of 1.02 kg/day and totaled 1,075 kg/ha; heifers gained 0.65 kg/day and totaled 673 kg/ha in summer and autumn. Weight gains for a 55‐day period in autumn were 71% greater than those for a comparable period in summer. It was concluded that this highly productive ecosystem should be extensively used for animal production.

Additional information on Mg status of temperate‐origin forages under cool temperatures is needed if economic losses from grass tetany are to decrease. A greenhouse study was conducted to determine temperature and Mg fertilizer effects on herbage Mg concentration of one or more cultivars of tall rescue (Festuca arundinaceaSchreb.), timothy (Phleum pratenseL.), reed canarygrass (Phalaris arundinaceaL.), smooth bromegrass (Bromus inermisLeyss.), orchardgrass (Dactylis glomerataL.), redtop (Agrostis giganteaRoth.), perennial ryegrass (Lolium perenneL.), Kentucky bluegrass (Poa pratensisL.), alfalfa (Medicago sativaL.), red clover (Trifolium pratenseL.), ladino and white clover (T. repensL.), alsike clover (T. hybridumL.), birdsfoot trefoil (Lotus corniculatusL.), and crownvetch (Coronilla variaL.). Plants were grown in Hagerstown soil, which belongs to the mixed, mesic family of typic Hapludalfs, in 4‐liter pots under natural daylength at cool (X̄ = 14 C), intermediate (X̄ = 18 C), and warm (X̄ = 26 C) ambient temperatures. Two levels of fertilizer Mg were used (0 and 672 kg Mg/ha as MgSO4). Grasses received 1,300 kg N/ha as NH4NO3and both grasses and legumes were supplied K2SO4to furnish 600 kg K/ha over a 13‐month growing period. Herbage was harvested at 2 to 3‐week intervals at a height of 5 cm. Under cool temperatures, in both spring and autumn, and with added Mg, cultivars having high Mg levels were ‘Timfor’ timothy, ‘Nordstern’ orchardgrass, and ‘Viking’ birdsfoot trefoil. Species and cultivar rankings were similar for spring and autumn but Mg concentration was greater in autumn, indicating that cool temperatures, per se may be less limiting to Mg accumulation than previously thought. Marked differences, five to seven‐fold, in Mg concentration occurred between species and cultivars of both grasses and legumes in response to Mg fertilizer. Low K/(Ca + Mg) ratios were obtained when the grasses were harvested under cool autumn temperatures. Yields were unaffected by Mg fertilization. The consistency of cultivar ranking for Mg levels over a wide temperature range and different soil Mg levels, suggest that cultivar selection for Mg accumulation would be rewarding. Cultivars inherently efficient in Mg uptake, especially at cool temperatures, may help prevent grass tetany.

Prices of both nitrogen fertilizers and forages have increased in recent years causing concern about the profitability of fertilizing forage grasses. Yield response functions, which permit computation of economic optima, were estimated using regression analysis for Kentucky bluegrass (Poa pratensisL.), tall fescue (Festuca arundinaceaSchreb.) orchardgrass (Dactylis glomerataL.), reed canarygrass (Phalaris arundinaceaL.), smooth bromegrass (Bromus inermisLeyss.), and timothy (Phleum pratenseL.). Experimental data from 3 years, 1968, 1969, 1970, with N treatments of 0, 112, 224, and 448 kg/ha were used to estimate the regression equations. Economic analyses were made with 3 N prices, 44, 55, and 66 cents/kg, and 5 forage prices, 2.2, 3.3, 4.4, 5.5, and 6.6 cents/kg. The economically optimal N treatment varied by species and was sensitive to changes in N‐forage price ratio, declining as the N price rose or the forage price declined. Fertilization with N was found to be profitable for all but very unfavorable price ratios.

The shortage of available forage during mid−summer is considered a major factor limiting the size of beef cowcalf herds in the Northeast. Consequently, using warmseason perennial range grasses as a supplement to existing cool−season grass forage programs is being considered. Animal feeding trials were conducted to assess the forage quality of ‘NY 1145’ big bluestem (Andropogon gerardiVitman), and ‘Blackwell’ switchgrass (Panicum virgatumL.) grown in Pennsylvania. Laboratory and animal estimates of digestibility were compared. Warm−season grass hays harvested at early head emergence, 2 weeks later, and at a regrowth stage in fall were fed with protein supplement to growing wether sheep in the first trial. In vivo digestible dry matter (DDM) of the hays ranged from 67 to 74%. Big bluestem and switchgrass DDM decreased 0.50 and 0.36 percentage units/ day, respectively, when harvest was delayed 2 weeks after head emergence, but dry matter intake (DMI) was not affected. Warm−season grass DDM and DMI were equal or superior to those for summer or fall harvested ‘Ky 31’ tall fescue (Festuca arundinaceaSchreb.). In the second trial, DDM of big bluestem and switchgrass hays harvested at early head emergence and fed to mature wether sheep without protein supplement ranged from 56 to 69%. Digestible dry matter and DMI for the warm−season grasses were generally lower than those for tall fescue harvested in spring at the same growth stage. In both animal studies, rankings of the grass hays using in vitro dry matter digestibility (IVDMD) and DDM estimates did not differ. The IVDMD technique did underestimate DDM by approximately 17 percentage units. This emphasizes the importance of animal evaluation in supporting laboratory forage quality analyses. Results suggest that big bluestem and switchgrass forage, harvested at early head emergence or later, appear most suitable for animals with lower nutrient requirements, such as beef cows.

Brassicaforage species may be used as alternative crops to provide supplemental herbage during the fall in the Northeast. However, these crops contain naturally occurring and potentially toxic constituents (glucosinolates and S‐methyl cysteine sulfoxide). Research was conducted to determine glucosinolate concentrations in 21 cultivars of five Brassicaspecies: turnip (Brassica rapaL.), rape (B. napusL.), kale (B. oleraceaL.), swede (B. napusL.), and Chinese cabbage type (B. cumpestris sensulatoL. ✕ B. rapaL.). Top (leaves plus stem), leaf (blade plus petiole), and root samples of each species were collected 60 or 90 days postseeding at Rock Springs, PA on a Hagerstown silt loam (fine, mixed, mesic Typic Hapludalf). Glucosinolates extracted from freeze‐dried, ground samples were bound to an anion exchange resin and hydrolyzed. The released glucose was quantified on an autoanalyzer. Of the five Brassicatypes, tops or leaves of kales had the lowest glucosinolate Concentration, 1.2 to 6.3 g kg−1; tops or leaves of rapes had the highest concentration, 2.9 to 11.9 g kg−1. Of the 21 cultivars, ‘Gruner’ and ‘Marrowstem’ kale, ‘Doon Major’ and ‘Calder’ swede, ‘Rangi’ rape, and ‘Sirius’ turnip had the lowest glucosinolate levels in tops and leaves; ‘Sipal,’ ‘Silona,’ and ‘Solo’ rape and ‘Green Globe’ and ‘York Globe’ turnip had the highest glucosinolate concentration. Roots of turnip and swede had glucosinolate concentrations as high or higher than those found in tops or leaves. All cultivars combined had significantly higher glucosinolate concentrations in 1980 than in 1979, and glucosinolate levels were significantly higher at 90 days than at 60 days postseeding each year. In a second field study, P and K fertilization at different rates only slightly increased glucosinolate concentration of ‘Fora’ rape, ‘Perko’ Chinese cabbage type, and Sirius turnip, whereas dry matter yields were dramatically increased (fourfold) by high N (132 kg N ha−1) and P (60 kg P ha−1). These data established that glucosinolate levels were sufficiently high (> 3 g kg −1) to produce inorganic isothiocyanate‐induced goiter (thyroid enlargement) in young growing sheep (Ovis aries) and cattle (Bos taurus). To minimize the potential for animal health problems, we conclude that Brassicaspp. should be fed in combination with other forages and that new varieties with reduced glucosinolate concentration should be developed.

Forage availability in summer is critical for sustaining high stocking densities of herbivores on pasture in the eastern U.S. The objective of this study was to determine forage productivity and quality of switchgrass (Panicum virgarumL.) and bluestems [Andropogon gerardiiVitman, Schizachyrium scoparium(Michx.) Nash, and Bothriochloa caucasica(Trin.) C.E. Hubb.] in summer. The experimental site was located in southwestern Pennsylvania on Guernsey silt loam (fine, mixed, mesic Aquic Hapludalf) soil. Two replicates, each containing eight warm‐season grasses with different proportions of volunteer cool‐season grasses and overseeded legumes were grazed from 1975 to 1977 and then harvested for hay in 1978 and 1979. Pastures were grazed each year in mid‐May, late July or early August, and early October. Nitrogen at 0, 45, and 90 kg ha−1and P at 0, 20,40 kg ha−1were applied to subplots. ‘Blackwell’ switchgrass and ‘Kaw’ big bluestem from the Great Plains readily established stands but did not persist as well as cultivars from the eastern USA. Total annual production from switchgrass‐dominated pastures was about 8.0 Mg ha−1and that from ‘NY 1145’ big bluestem was 6.0 Mg ha−1, Over a 4‐yr period, NY 1145 produced about 70% more forage in late July than did Kaw big bluestem. Mean yield distribution of the switchgrass and bluestem pastures was approximately 15% in May, 55% in July‐August, and 30% in October. July yield increased about 11 kg kg−1of N applied. Mean in vitro dry matter disappearance (IVDMD) values for switchgrass and bluestem ranged from 470 to 570 g kg−1,, but it was determined that IVDMD under‐estimated in vivo digestibility by 100 to 200 g kg −1, Crude protein concentration ranged from 70 to 120 g kg−1, Mean crude protein concentration of grass fertilized with 45 and 90 kg N ha−1over a 3‐yr period was 10 and 26% higher, respectively, than that for unfertilized grass. Overseeded legumes, especially red clover (Trifolium pratenseL.), established good stands in warm‐season grasses with < 75% stands. Mixed stands of warm‐ and cool‐season grasses and legumes can be maintained under grazing or hay production, with a substantial shift in seasonal yield distribution that can be very beneficial to beef (Bos taurus) producers.

Production of cool‐season (C3) herbage generally is low in summer and fall in the humid eastern USA. This study was conducted to determine the yields and pest problems of spring‐sown turnip, Brassica rapaL.; swede, B. napusL.; rape, B. napusL.; interspecific crosses between Chinese cabbage, B. campestris sensufaioL., and turnip or rape; or kale, B. oleraceaL., that were stockpiled. The crops were no‐till seeded (turnip and swede at 1.4 kg ha−1, rape, the hybrids, and kale at 4.2 kg ha−1) into mature alfalfa (Medicago sativaL.)‐grass stands. Prior to seeding, the sod was treated with isopropylamine salt of N‐(phosphonomethyl) glycine at 1.1 kg a.i. ha−1. The study was made in central Pennsylvania on Hagerstown silt loam (fine, mixed, mesic Typic Hapludalfs) soil in 1979 and 1980 and on Hublersburg silt loam (clayey, illitic, mesic Typic Hapludults) soil in 1981. Dry matter yield determinations were made sequentially at 30‐day intervals from 60 to 150 days post‐seeding. Fertilizer (P and K) was applied according to soil test results and 80 kg N ha−1was applied at seeding and 70 kg N ha−1between the 60‐ and 90‐day sampling dates. Three‐year mean dry matter yields for 13 of 19 cultivars exceeded 7.0 Mg ha−190 days post‐seeding. Yields plateaued from 80 to 160 days depending on plant species, cultivar, and year. Cultivar (across species) ✕ sampling date, turnip cultivar ✕ year, and swede, rape, and kale sampling date ✕ year interactions were significant for yield. Incidence of plant diseases was positively related to slowing of growth at physiological maturity. Some New Zealand turnip and rape cultivars were more resistant to flea beetle [Phyllotreta cruciferaeGoeze and P. striolata(Fab.)] than cultivars of European origin. Crude protein concentration of turnip and Chinese cabbage hybrid tops was higher at 120 than 90 days, but it was not for other species. Crude protein concentration ranged from 110 g kg−1in roots of certain cultivars to 270 g kg−1in turnip tops. Species ✕ sampling date and year ✕ sampling date interactions were significant for crude protein concentration and in vitro dry matter disappearance (IVDMD). The IVDMD values ranged from 800 to 930 g kg−1Kale had the lowest mean IVDMD, 840 g kg−1.

Hypomagnesemic tetany, in both spring and winter forms, is a serious metabolic problem in beef cow herds in the northeast U. S. Control of the syndrome may be achieved by Mg supplementation of the diet, by selecting or breeding plants with the ability to accumulate Mg, or by increasing the concentration of Mg in forages by Mg fertilization or foliar application. The present study was designed to determine whether fertilization of forages with a moderate level of an available Mg fertilizer would effectively increase the concentration of Mg in the forage and improve the Mg status of ruminant animals. A number of grasses and legumes were grown in Pennsylvania and West Virginia, fertilized with kieserite (MgSO4·H2O) at the rate of 112 kg Mg/ha, and harvested as hays in 1973 and 1974. Magnesium concentration in the forages was determined by chemical analysis, and utilization of minerals evaluated with growing wether lambs in balance trials. The use of the guinea pig (Cavia porcellus) as an assay animal for mineral studies with ruminant species was examined in a limited number of trials. Magnesium fertilization increased the concentration of Mg in hays, from a mean value of 0.17 to 0.20% for all forages studied. Fertilization had no significant effect on dry matter digestibility (DMD) of the hays by lambs, and had a variable effect on apparent absorption of Mg. Apparent absorption of Mg was increased significantly, from 24.4 to 29.5%, by fertilization of the grass hays, with no effect (31.8 vs. 31.9% for non‐fertilized and fertilized treatments) in the legume hays. Apparent absorption of Mg, Ca, and P was higher in legumes than in grasses, but there were no differences in absorption of K and S due either to type of hay or to fertilization. Magnesium fertilization resulted in a highly significant increase in Mg retention by lambs, 0.17 vs. 0.28 g/day for non‐fertilized compared to fertilized treatments, for all forages. Retention of Mg, Ca, and P was markedly higher from the legume than from the grass hays. Fertilization had no effect on retention of Ca or P. Fertilization resulted in the most marked improvements in Mg retention from orchardgrass (Dactylis glomerataL.) when harvested (1974) at a vegetative stage in West Virginia and Pennsylvania. DMD values of forages were lower, and apparent absorption and retention of Mg much higher, in the guinea pig than in the lamb in comparative trials. Substantial species differences in the degree and nature of Mg utilization of alfalfa (Medicago sativaL.) hays fertilized with different levels of MgSO4suggest that the guinea pig would not be a suitable essay animal for mineral availability studies with the ruminant.

This investigation was part of a continuing effort to ascertain the role of soluble proteins in the development of cold tolerance of alfalfa, Medicago sativaL. The research was conducted to determine whether certain soluble proteins, known to be closely associated with the development of cold tolerance, exhibited hydrolytic enzyme activity. Cold‐tolerant ‘Vernal’ and cold‐sensitive ‘Sonora’ alfalfa plants grown for 66 days under simulated “summer” (nonhardening) and “winter” (hardening) conditions exhibited different levels of cold tolerance as indicated, by cold tolerance assays performed at three freezing temperatures. Sonora winter plants were only moderately tolerant to −6 C, whereas Vernal plants were well hardened to −8 C and were tolerant to −10 C. Soluble protein concentrations were higher in hardened than in unhardened plants, with differences in protein concentration greater for Sonora than Vernal. Localization of hydrolytic enzymes on polyacrylamide gels after disc electrophoresis and subsequent densitometric scanning of zymograms demonstrated that activities of amylases, leucine amino peptidases, and α‐esterases were greater in winter than summer samples of both cultivars; whereas ATPase activities were lower in winter than summer samples. Furthermore, differences between αaesterase levels of hardened and unhardened samples were greater than those of amylase or peptidase. New esterase forms and higher quantities of a heat‐stable amylase also were detected in hardened samples. Differences in enzyme solubility between distilled water and tris‐HCl extracts, related to environment, extractant, or cultivar influences, were evident for esterases and ATPase and for individual forms of amylase and peptidase. The large quantitative changes in amylases and esterases localized within gel column regions 7 and 8 of hardened Vernal zymograms implied a close relationship of these hydrolytic enzymes to the hardening process; whereas the decreased ATPase activities reflected an inverse relationship with cold tolerance. It is, therefore, reasonable to conclude that quantitative and qualitative differences in hydrolytic enzyme activity are evident between hardened and nonhardened plants. The differences among hydrolytic enzymes do not necessarily follow the same quantitative or qualitative pattern, and for this reason they should be studied collectively to understand the biochemistry of hardening.

Certain soluble proteins are believed to be closely associated with cold tolerance. The objectives of this work were to determine whether the proteins exhibited dehydrogenase activity and if there were qualitative and/or quantitative differences in dehydrogenases between hardened and nonhardened plants. Cold‐tolerant ‘Vernal’ and cold‐sensitive ‘Sonora’ alfalfa (Medicago sativaL.) plants were grown for 66 days under simulated summer (non‐hardening) and winter (hardening) conditions, using growth chambers, and were assayed for the levels of cold tolerance developed at three freezing temperatures (−6, −8, and −10 C). To determine differences in dehydrogenases, soluble proteins were separated from extracts of crown and root tissues by polyacrylamide disc gel electrophoresis. Localization of dehydrogenases on gels and densitometric scanning of zymograms indicated that activities of glutamate, lactate, isocitrate, glucose‐6‐phosphate, 6‐phosphogluconate, nicotinamide adenine dinucleotide (NAD) malate and nicotinamide adenine dinucleotide phosphate (NADP) malate dehydrogenases were high in both cultivars exposed to hardening and were generally highest in Vernal. Percent increases for winter over summer levels of glutamate, lactate, glucose‐6‐phosphate, and 6‐phosphogluconate dehydrogenases were large compared with those of isocitrate, NAD‐malate, and NADP‐malate dehydrogenases. Moreover, the magnitude of change in enzyme activity between summer and winter plants also was influenced by extractant (distilled water, pH 7 or 0.10 Mtris‐HCl, pH 7) and varied quantitatively according to the solubility of the dehydrogenases in the two extractants. Enzyme solubility differences related to cultivar or environmental influences and cold tolerance were also observed, especially for isocitrate dehydrogenase. Large quantitative differences in glucose‐6‐phosphate and lactate dehydrogenase activities and substantial increases in isocitrate and 6‐phosphogluconate dehydrogenases localized within gel column regions 7 and 8 of zymograms developed from winter samples implied a close relationship of these enzymes to cold tolerance. Forms of lactate, glucose‐6‐phosphate, and isocitrate dehydrogenases were present in hardened tissues that were not present in un‐hardened tissues. It is concluded that the observed differences in dehydrogenasees between hardened and non‐hardened plants are major indicators of the cold tolerant state. Based on these and past studies, the reactions analyzed by representative hydrolytic and dehydrogenase enzymes may serve as a working hypothesis for future studies concerning the mechanics of induction and the suspected catenary nature of the hardening process.

This research was undertaken to assess the influence of harvest schedules and fertilization on the persistence and productivity of four warm‐ and six cool‐season grass species under minimal temperature and moisture stresses. The grasses were clipped three, five, or eight times during each of 2 years. The first clipping each year was taken on April 26, May 7, or June 10 and aftermath clippings were taken at 21‐, 35‐, or 55‐day intervals, respectively. Ammonium nitrate was applied in three equal applications during each growing season. A total equivalent of 168 or 336 kg/ha was applied to each plot. Persistence of Kentucky bluegrass (Poa pratensisL.), tall fescue (Festuca arundinaceaSchreb.), orchardgrass (Dactylis glomerataL.), and Timothy (Phleum pratenseL.) improved as clipping frequency was increased from three to eight cuts per year, especially at the high rate of N. Reed canarygrass (Phalaris arundinaceaL.) and smooth bromegrass (Bromus inermisLeyss.) stands were better if clipping was less frequent. Stands of bermudagrass [Cynodon dactylon(L.) Pers.], indiangrass [Sorghastrum nutans(L.) Nash], big bluestem (Andropogon gerardiVitman) and switch‐grass (Panicum virgatumL.) had deteriorated badly after 2 years, regardless of treatment. Orchardgrass was the most productive species overall and was least affected by the clipping and fertilizer treatments. Dry matter yields of grasses in the second harvest year were differentially influenced by clipping and nitrogen fertilizer (3‐factor interaction = P < .005). At the high rate of N, orchardgrass, reed canarygrass, and smooth bromegrass yields were highest with three clippings, tall fescue and timothy yields were highest with five clippings, and Kentucky bluegrass yields were highest with eight clippings. At the low rate of N all species, except Kentucky bluegrass and timothy, produced highest yields with three clippings. Timothy yields were highest with five clippings, and clipping frequency had little effect on bluegrass yields. Yields were reduced most by infrequent clipping at the high rate of N (Kentucky bluegrass, tall fescue, timothy) and by frequent clipping at the low rate of N (all species except bluegrass). Persistence and yield distribution responses to clipping and nitrogen fertilizer were different from those commonly reported for lower elevations and were attributed to less temperature and moisture stress. Management requirements for warm‐season grasses differ from those for cool‐season grasses and need to be studied in more detail.

‘Chaining’ crownvetch (Coronilla variaL.) was grown at four West Virginia locations: Morgantown, Wardensville, Reedsville, and Point Pleasant. These locations vary in amount and distribution of rainfall, temperature, snow cover, and length of growing season and show how combinations of environmental factors affect yield, morphology, and carbohydrate reserves. Yield and bud activity as affected by cutting at different growth stages and heights are presented. The effect of two and three harvests per season on yield and fall carbohydrate levels was also studied. Yields varied greatly among locations and years. Greater than 10,000 kg/ha were produced at Morgantown in 1969 and Reedsville in 1970 compared with total yields at Point Pleasant of 2,000 to 4,000 kg/ha from a thin stand. Greater yields generally were produced by two rather than three harvests per season. Clipping to stubble heights of 7.5 or 15.0 cm resulted in similar yields. First cutting yields generally increased as the first harvest was delayed to full bloom (mid‐June); however, delaying harvest past this period seldom increased yield. Cutting treatments did not detrimentally affect any of the stands, except possibly at Morgantown, where general vigor of the stand was lower the second season. The proportion of axillary buds producing growth increased with delay of spring harvest until full bloom and then declined. Delay of the first cutting and adequate moisture increased the proportion of axillary buds that produced regrowth. Cutting at different stubble heights generally had no effect on activation of axillary buds. Initiation of growth from crown buds was determined 2 weeks after cutting. Active buds at the crown and up to 2.5 cm from the base of 100 randomly selected stems were counted. Growth initiation from crown buds was greater when plots were cut at 7.5 cm than when cut at 15.0 cm for most cutting dates and locations. Crown bud activity was generally less during early spring and periods of moisture stress. Total non‐structural carbohydrates (TNC) in autumn were similar among locations. Slightly higher TNC values were associated with the 15.0 cm cutting heights, due mainly to changes in starch levels.

Native perennial warm‐season grasses are established and used in the northeastern United States for beef cattle (Bos taurus) production, wildlife habitat, and soil conservation. This research was conducted in Pennsylvania to study select plant growth responses and forage quality of switchgrass (SWG), Panicum virgatumL., and big bluestem (BBS), Andropogon gerardiiVitman, to dolomitic lime, and P and N fertilizers on strongly acid, fine‐loamy, mixed, mesic, Typic Fragiaqualfs. The soil amendments were applied after the first growing season. Growth of SWG and BBS was markedly improved by topdressings of lime and N fertilizer. In 1981 and 1982, untreated warm‐season grass yielded approximately 50%, and grass receiving the low rate of applied nutrients yielded 90%, of that with the high lime and fertilizer rate (8.76 Mg ha−1). Nitrogen fertilizer increased production of stems and leaf sheaths more than leaf laminae. Crude protein concentration (CPC) of both species generally was low, but N fertilizer increased CPC from 52 to 77 g kg−1. In vitro dry matter disappearance values were low, but significant species X N, lime X N, species X lime X N, and N X year interactions occurred. Lime effects were significant for concentrations of Ca, Mg, and Mn; P fertilizer for Ca, Mg, and P; and N fertilizer for Ca, Mg, P, and Mn. Aluminum concentrations in forage were low even with an exchangeable soil Al of 100 kg ha−1. Approximately 80% of the root mass of each species was within the top 10 cm of soil, but roots were observed growing along prism faces of the fragipan at 60 cm. The warm‐season grasses were productive on strongly acid (31 Mg lime ha−1needed for neutralization), infertile soil, with low inputs of lime (4.5 Mg ha−1) and fertilizer.

Millions of hectares of pasture in the Northeast have low available soil P levels. Introducing forage species that produce well on these soils could increase forage production with minimum economic input. The objective of this study was to compare the performance of warm and cool‐season grasses under low or high available P. Several warm and cool‐season forage grasses were grown on a Berks shaly silt loam soil (Typic Dystrochrept; fine, loamy, skeletal, mesic), low in native available P (5 ppm Bray and Kurtz #1 extractable P), with and without added P. The warm‐season grasses included two Old World bluestems, ‘Caucasian’ Bothriochloa caucasica(Trin.), C. E. Hubb. and “B”‐strain, B. intermedia(R. Br.) A. Camus; three big bluestem cultivars, Andropogon gerardiVitman; three little bluestem cultivars, Schizachyrium scoparium, Michx.; six switchgrass cultivars, Panicum virgatumL.; and two indiangrass cultivars, Sorghastrum nutans(L.) Nash. The cool‐season grasses were Ky 31 tall fescue, Festuca arundinaceaSchreb., ‘Pennlate’ orchardgrass, Dactylis glomerataL., and ‘Tioga’ deertongue grass, Dichanthelium clandestinum(L.) Gould. Yields of most warm‐season grasses nearly doubled from 1977 to 1978, whereas yields of the cool‐season grasses decreased. Forage yields and P concentrations of all cultivars generally were greater with applied P both years. At the low P level, warm‐season grass yields in the second year were up to three times higher than yields of cool‐season grasses, whereas P concentrations in forage of cool‐season grasses were twice those of warm‐season grasses: The warmseason grasses, Ky 729 and ‘Blackwell’ switchgrass, Ky 2 Caucasian and B‐strain Old World bluestems, and NJ 1617‐72 indiangrass absorbed more total P than all other cultivars. Warm‐season grasses had relatively low crude protein and IVDMD levels, ranging from 4.7 to 8.5% and 34.0 to 52.3%, respectively. Of the warm‐season grasses, Old World bluestems, Caucasian and B‐strain, had the highest IVDMD values, 52.2 and 51.2%. The cool‐season grasses had an average crude protein level of 14.6% and IVDMD value of 59.4%, respectively. The two Old World bluestems, Ky 729 and Blackwell switchgrasses, and NJ 1617‐72 indiangrass appear to have the highest potential to produce forage on soils with low levels of available P.

A balanced forage program should include species that provide the highest yields of quality forage throughout the grazing period. In the Northeast, where cool‐season grasses predominate, the short supply of forage during summer limits beef cow‐calf herd size. Warm‐season (C4) perennial grasses are productive in midsummer and may supplement temperate species for grazing and hay. ‘NY 1145’ big bluestem (Andropogon gerardiVitman) and ‘Blackwell’ switchgrass (Panicum virgatumL.) were grown on soils (Aeric Fragiaquualt and Aquic Hapludalf) low in available P at two locations in Pennsylvania to characterize changes in quality of leaf and stem tissue associated with maturation. Forage was harvested at 10‐day intervals beginning at the 3‐ to 4‐leaf stage in late June and continuing until seed set in early August. Percentage leaf tissue declined similarly with maturation for the two grasses. Leaf dry matter yields were approximately twice those of stems in June but the opposite was true in August. At early head emergence, percentage leaf tissue for big bluestem and switchgrass averaged 34 and 44%, respectively. Averaged over grasses, leaf and stem forage quality estimates at early head emergence, respectively, were: crude protein (CP), 9.7, 4.3% in vitro dry matter disappearance (IVDMD), 60.4, 50.0%; neutral detergent fiber (NDF), 66.0, 75.3%; lignin, 4.7, 7.2%; and phosphorus (P), 0.20, 0.16%. Big bluestem leaves were higher in CP but lower in NDF than switchgrass leaves. Stem tissue of big bluestem was lower in NDF but higher in lignin than that of switchgrass. The decline in leaf and stem CP, IVDMD, and P with maturation was less pronounced in leaf tissue. The increase in NDF and lignin with maturity was greater in stems than in leaves. Fiber accumulation in stem tissue continued after seedheads emerged and was accompanied by decreases in CP and IVDMD. At early vegetative stages, the high percentage of good quality leaf tissue suggest the potential use of big bluestem and switchgrass for ruminants with above maintenance energy requirements. However, at later growth stages (late joint early head), the increase in stem tissue and associated decline in nutritive value suggest using these grasses either for grazing or hay by ruminants to meet only maintenance energy needs.

Most grass species are not highly compatible with alfalfa, Medicago sativaL., in a mixture, either because they do not persist under certain harvest schedules or they are too competitive and are not readily acceptable to grazing animals. This study compared perennial ryegrass, Lolium perenneL., with orchardgrass, Dactylis glomerataL., each in combination with alfalfa under grazing situations. Dry matter yields, herbage nutritional value, changes in botanical composition, alfalfa persistence, animal acceptance, and average daily weight gains (ADG) of beef cows and calves were recorded. ‘Terhoy’ and ‘Reveille’ perennial ryegrass and ‘Pennlate’ orchardgrass were planted with ‘Saranac‐AR’ alfalfa at 17, 17, 7, and 11 kg.ha−1, respectively. The grass‐alfalfa stands were established on Hagerstown silt loam (fine, mixed, mesic Typic Hapludalf), and on Hublersburg silt loam (clayey, illitic, mesic, Typic Hapludult). A four‐paddock rotational grazing system was used with each mixture, with an average of 12 days grazing paddock−1and a 36‐day rest period. There were 117 days of grazing in 1978 using four tester beef cows and calves per mixture and 163 days of grazing in 1979 using five tester beef cows and calves per mixture. Additional animals were added as needed to equalize grazing pressure. Herbage yield and quality samples were taken before grazing in each paddock. In 1979, additional herbage samples were taken after animals were removed from a paddock. Annual dry matter yields for 1978 and 1979 were not significantly different for the three mixtures. Mean herbage crude protein concentrations were: alfalfa, 22%; ryegrass, 20%; and orchardgrass, 16%. Reveille‐alfalfa and Terhoy‐alfalfa pastures produced 473 and 320 kg more herbage protein.ha−1.year−1, respectively, than orchardgrass‐alfalfa pastures. Mean in vitro dry matter digestibility was: ryegrass, 77%; alfalfa, 73%; and orchardgrass, 70%. Reveille ryegrass‐alfalfa and Terhoy ryegrass‐alfalfa produced 886 and 331 kg more digestible dry matter.ha‐1.yr‐1, respectively, than orchardgrass‐alfalfa. Orchardgrass contributed 50 and 80% of the dry matter yields in May of 1978 and 1980, respectively, whereas ryegrass contributed 35 to 40% of May dry matter yields each year. After 2 years of grazing, ryegrass pastures contained 53% more alfalfa plants than orchardgrass pastures. Animal preference was ryegrass > alfalfa » orchardgrass. Composition of stubble remaining after grazing averaged 28% ryegrass‐62% alfalfa vs. 74% orchardgrass‐24% alfalfa. The ADG of beef cows and calves were influenced by a) pretrial diet, b) plant maturity, c) a changing environment that influenced botanical and chemical composition of forage components and animal metabolism, d) age of animals, and e) cow‐calf interactions. In 1978, ADG means were not significantly different for cows or calves on the three grass‐alfalfa mixtures. In 1979, the combined ADG of cows and calves on the ryegrass‐alfalfa mixtures averaged 21 % higher than those of cows and calves on orchardgrass‐alfalfa. Ryegrass‐alfalfa mixtures should be widely tested under different soil and weather conditions in the humid U.S.A. to determine areas of adaptation. Where adapted, ryegrass‐alfalfa mixtures offer substantial potential contributions to forage‐animal production systems and economies.

Zinc concentrations in temperate origin perennial grasses do not always meet recommended nutritional requirements for animals. Availability could be affected by factors which contribute to lignification which reduce forage digestibility, and possibly, availability of minerals including Zn. A field plot study was established on Hagerstown silt loam (Typic Hapludalf fine, mixed, mesic) where Zn concentration and Zn water solubility was determined in vegetative material of two cultivars of each of six temperate origin perennial grasses collected in May, August, and October of 1971 and 1972. Total Zn concentrations were positively correlated (P < 0.01) with water soluble Zn especially in material produced in August and October. Total Zn concentrations and percentage Zn solubility [(water soluble Zn/total Zn) ✕ 100] were inversely related among species; for example, reed canarygrass (Phalaris arundinaceaL.) ranked first among the species for total Zn (23 ppm) and last for percent solubility (61%), while tall fescue (Festuca arundinaceaSchreb.) ranked last among the cultivars for total Zn (15 ppm) and first for solubility (84%). Total Zn concentrations were positively correlated (P < 0.01) with in vitro dry matter digestibility; Zn solubility (%) was not. The data show Zn concentrations vary with season and that all species and cultivars do not exhibit the same pattern of variation. Therefore, careful species and cultivar selection should be considered, particularly where there is evidence of Zn inadequacy in ruminant diets.

Crownvetch (Coronilla variaL.) has not been widely used for forage, partly because its forage quality has been reported as poor. Studies were undertaken to determine the effects of different environments and clipping schedules on composition and in vitro digestibility of crownvetch stems and leaves. First growth was sampled from flower bud to seedpod growth stage, and regrowth was sampled in July and September. Identical cutting schedules were used at four field locations in West Virginia for 2 years. Also, in growth chambers, controlled day‐night temperature combinations of 16‐2, 16‐10, 16‐18 C; 21‐2, 21‐10, 21‐18 C; and 38‐2, 38‐10, and 38‐18 C were used to determine temperature effects on herbage comosition. Acid detergent fiber and permanganate lignin levels in crownvetch were influenced differently by environment than were their deposition rates. High leaf ADF and lignin levels were attributed to high light intensities within the crownvetch canopy. Stem ADF averaged 18% higher and leaf ADF 36% higher in first regrowth than in second regrowth. Leaf lignin averaged 67%, higher in fist regrowth than in second regrowth. Leaf lignin levels of crownvetch under controlled temperatures and low light intensities were one‐fourth to one‐half of that in field samples. Maturity effects on ADF and lignin levels were significantly greater at the two locations with higher elevations. The ADF and lignin deposition rates in late spring 1970 averaged three times those in 1969 and were associated with higher rainfall. Cutin level of leaves was 65% higher than that of stems, and maximum levels were obtained either at early or full bloom stage. In vitro digestibility of crownvetch stems decreased 0.81 percentage points per day from flower bud to early bloom, and thereafter at lower rates. Digestibility of crownvetch stems and leaves of first regrowth (58, 74%) was lower than that of second regrowth (66, 78%). The ADF and lignin levels of stems, but not of leaves, were largely independent of crop yield and were inversely related to digestibility. Prediction of nutritive value of firstcrop crownvetch is far more difficult than of other commonly used legumes

Low Ca and P levels and wide Ca:P ratios of forages have been implicated in several animal diseases of economic importance. However, information on seasonal, temperature, and soil amendment effects on Ca and P levels and ratios of forages of different species and cultivars is meager. A greenhouse study was conducted to determine seasonal, temperature, soil pH, and Mg fertilizer effects on herbage Ca and P levels and Ca:P ratios in one or more cultivars of tall fescue (Festuca arundinaceaSchreb.), timothy (Phleum pratenseL.), reed canarygrass (Phalaris arundinuceaL.), smooth bromegrass (Bromus inermisLeyss.), orchardgrass (Dactylis glomerataL.), redtop (Agrostis giganteaRoth.), perennial ryegrass (Lolium perenneL.), Kentucky bluegrass (Poa patensis L.), alfalfa (Medicago sativaL.), red clover (Trifolium pratenseL.), ladino and white clover (T. repensL.), alsike clover (T. hybridumL.), birdsfoot trefoil (Lotus corniculatusL.), and crownvetch (Coronilla variaL.). Plants were grown in 4‐liter pots containing Hagerstown silt loam (Typic Hapludalf; fine, mixed, mesic) under natural daylength and near‐ambient air temperatures. Minimum temperature was not permitted to drop below 1 C. Initial soil pH levels were 6.0 and 7.0 in combination with 0 and 672 kg Mg/ha (as MgSO4). During a 13‐month growing period, grasses received 1,300 kg N/ha (as NH4NO3), and grasses and legumes were provided 600 kg K/ha (as K2BO4). Plants were clipped to 5 cm, generally at 2 to 3‐week intervals. During semidormancy, plants were harvested at longer intervals but not analyzed. Grasses and legumes, except white clover, had higher Ca and lower P levels (P < 0.01) in late autumn than in May under similar temperature regimes. During periods of alternating cool and intermediate temperatures, Ca levels of grasses and legumes were higher (P < 0.01) with the intermediate temperatures. As the average air temperature increased from 17 to 26 C, Ca levels of grasses and legumes and P levels of legumes increased or decreased depending on the species, but P levels of grasses decreased. Differences in Ca levels of grasses and legumes that were related to increased Ca saturation percent of the soil CEC, varied markedly in magnitude depending on the species and cultivar. Increased Mg saturation of the soil CEC above 13 and 22% lowered Ca levels and Ca:P ratios of grassa and legumes, respectively. Redtop was the best and Kentucky bluegrass the poorest Ca accumulator among grasses. Penngift crownvetch was the best Ca accumulator and Vernal alfalfa and birdsfoot trefoil were poor accumulators among legumes. Grass cultivars did not differ consistently in P accumulation. Vernal alfalfa was the best and Regal white clover was the poorest P accumulator. Average Ca:P ratios of grasses were generally low, and legumes ranged from 2.5:l for Vernal alfalfa to >4.01 for the white clovers and Penngift crownvetch. With high Ca saturation percent of the soil CEC, many Ca:P ratios in autumn were above 4.01 for grasses and above 8.0:l for legumes.

Insufficient herbage during the fall in the temperate areas of the world has long been a serious limitation in animal production. The purpose of this research was to determine the feasibility of producing Brassicaspp. forage crops for fall grazing of sheep on hill land. The experiment was conducted near Waynesburg, Pa., in a 4‐ha hill pasture, predominantly Dormont silt loam (fine‐loamy, mixed, mesic Ultic Hapludalf) on the sideslopes and Culleoka loam (fine‐loamy, mixed, mesic Ultic Hapludalf) on the ridge. A split‐plot block arrangement was used with blocks of ‘Sirius’ turnip, (Brassica rapaL.) ‘Fora’ rape, (B. napusL.), and ‘Perko P.V.H.’ winter rape (B. rapaL.) randomized in each of six blocks. Competition from the existing species was suppressed with paraquat (l,l′‐dimethyl‐4,4′‐bipyridinium ion) or glyphosphate [isopropylamine salt of N‐(phosphonomethyl)glycine] at 1.1 kg a.i. ha−1. Nitrogen and P fertilizer treatments were assigned to subplots in a randomized complete block design. Fertilizer was applied before seeding in 1978 and 1979 to provide 0, 33, 66, 99, or 132 kg N ha−1and 0, 15, 30, 45, or 60 kg P ha−1in a 52factorial arrangement. The crops were minimumtillage (min‐till) planted on 10 Aug. 1978 and 25 July 1979. Dry matter (DM) yields were determined 60 and 90 days after planting. Select samples were taken to determine crude protein, in vitro dry matter disappearance (IVDMD), and mineral element composition. Mean crop yields were similar for the two herbicide treatments in 1978 but were−35 to 75% higher on glyphosate‐treated plots than on paraquat‐treated plots in 1979. Grass yield in the Brassicaplots in 1979 were twice as high in the paraquat‐treated plots as in the glyphosate‐treated plots. At the higher rates of applied N and P, DM yield exceeded 7000 kg ha−1in 1978 and 9000 kg ha−1in 1979. Crop yield responses were quadratic functions for N fertilizer rates and linear functions for P fertilizer rates for both harvests in 1978. In 1979, yield responses were linear functions for N fertilizer rates for both harvests and for P fertilizer rates for the 60‐day harvest; and were quadratic for P rates for the 90‐day harvest. Yield of turnip and rape was affected more by P fertilizer before the 60‐day harvest than afterwards. Crude protein concentration ranged from 60 to 250 g kg−1. Nitrogen and P fertilizers differentially affected the crude protein concentration of forage turnip and rapes. Mean IVDMD was 950 and 900 g kg−1for turnip tops and roots, respectively, 910 g kg−1for Fora rape, and 930 g kg−1for Perko rape. Yield of digestible DM of turnip was up to 67% higher than that of stockpiled orchardgrass. The Brassicaspp. had different DM mineral element compositions, and concentrations of P, K, Ca, Mg, and Zn generally were higher in Brassicaspp. than in orchardgrass checks.

Timothy (Phleum pratenseL.), bromegrass (Bromus inermisLeyss.), orchardgrass (Dactylis glomerataL.) and Kentucky bluegrass (Poa pratensisL.) were grown at four locations in West Virginia with and without supplemental water and at three levels of fertility during August of 1964 and 1965. The dry weight of top growth produced at each location depended upon species, moisture, fertility, temperature, and combinations of these factors. The addition of either water or fertilizer alone often did not significantly increase yields, but a combination of these two factors usually increased yields. When the moisture supply was low and temperatures high, the addition of fertilizer decreased yields. The location where the most top growth was produced, when no supplemental water was added, was usually the location receiving the most precipitation. When supplemental water was added, the most favorable location depended upon the temperature. All species except bromegrass produced high yields at the location having the coolest temperatures, whereas bromegrass often produced its lowest yields under these conditions. A temperature of −0.6 C was detrimental to timothy as well as bromegrass. The level of food reserves as indicated by etiolated growth was greatly affected by temperature and moisture. As the maximum temperature increased, the level of reserves decreased. The response due to supplemental water was highly dependent upon natural precipitation. The top growth and etiolated growth produced under natural climates were compared with that produced under controlled climates. A discussion of trends and limitations of such comparisons is given.

The growth of timothy (Phleum pratenseL.), bromegrass (Bromus inermisLeyss.), orchardgrass (Dactylis glomerataL.), and Kentucky bluegrass (Poa pratensis,L.) was studied under controlled temperatures varying by 3.3 C intervals from 18.3 to 34.8 C during the day and from 1.8 to 18.3 C during the night. A day temperature between 18.3 and 21.6 C was optimum for top growth with timothy, orchardgrass, and bluegrass. With bromegrass, the optimum day temperature was between 18.3 and 24.9 C. As the day temperature was increased from these optimum ranges to 34.8 C, all of the species decreased in yield, but the decrease in bromegrass yields was less than in any of the other species. In some cases, night temperature also affected yields; but the optimum night temperature depended upon the species and the day temperature. The dry weight of etiolated growth indicated that the level of food reserves varied greatly. The species ranked orchardgrass > bromegrass > bluegrass > timothy for level of reserves. The most important factor affecting the level of reserves in a particular species was night temperature. In general, the food reserves decreased as the night temperature was increased from 1.8 to 18.3 C.

A study was made of the nutritive quality of orchardgrass fertilized at four nitrogen levels (0, 56, 168, and 504 kg/ha) and either free‐grazed or zero‐grazed by sheep at four periods of the year (May, June, September, March). Effects of fertilization and growth period on nitrogen, fiber, and mineral components of the herbage were noted. In trials with cut herbage fed ad libitumto sheep indoors, level of fertilization had a significant effect on protein digestibility but little effect on dry matter and cellulose digestibility or on intake. Consumption levels of the harvested grass were higher in June than in May or September, and there was a marked decline in both the digestibility and intake of frost‐killed herbage in March. A hay cutting made from first growth grass at the end of the grazing trials in May showed decreases of approximately 15% in digestible dry matter and 40 to 45% in intake when compared to cut herbage. Regressions calculated between dry matter digestibility and percentage of fecal nitrogen in the indoor trials were found to have a seasonal bias. The differences between digestibility coefficients as measured directly with cut herbage and as estimated by regression for grazing animals were most marked in the May and March trials, with approximate increases of 8 to 15 percentage units due to selection. Differences with regrowth herbage in June and in September were minor. The estimated consumption of orchardgrass by grazing sheep tended to decline from period to period, and there were significant effects of level of nitrogen fertilization on intake. An increase in intake associated with nitrogen fertilization was most evident in the May and March growth periods. Nitrogen fertilization also improved the relative acceptance of herbage as measured in palatability experiments with grazing sheep. A comparison of the intake of digestible dry matter by sheep under the free‐grazing or the zero‐grazing systems indicated significantly higher values for the grazing animals in the May, September, and March growth periods. No differences were apparent on regrowth herbage in June.

The influence of fertilizer treatment and growth stage on the composition and nutritive value of tall fescue grazed or fed as cut herbage to sheep was examined in first growth and regrowth pasture. Analysis of clipped herbage showed effects of growth stage and fertilizer treatment on plant content of protein, fiber fractions, soluble carbohydrate and certain macro elements, but little consistent effect on trace minerals. With clipped herbage, fertilizer and growth stage altered dry matter and protein digestibility. Fertilizer had little effect on ad lib. intake; intake declined with advancing maturity in the first growth herbage, but there was no effect of date of cutting on intake in the regrowth trials. The dry matter digestibility of grazed herbage was calculated by use of fecal N as an indicator in “local” regressions. The relationship between digestibility and fecal N was found to be affected by growth phase (first cuttings vs regrowth), but not by fertilizer treatment. Calculated dry matter digestibility coefficients averaged 2% higher for grazed than for clipped herbage. Estimated intake values for grazing sheep indicated that cutting date had no effect on intake within first growth or regrowth trials, but that herbage fertilized with higher levels of nitrogen, or nitrogen plus phosphorus, was consumed in greater amount than nonfertilized grass, or grass treated with phosphorus or potassium alone. Grazing sheep in palatability trials showed a marked preference for fescue fertilized with nitrogen, or nitrogen plus phosphorus. Correlation analyses of nutritive criteria with plant composition showed significant relationships between the dry matter digestibility of clipped or grazed herbage and the content of dry matter, crude protein or fiber fractions, but little apparent effect of most plant components on intake.

Cold resistance increased from late September to mid‐December. A high level was maintained until February or early March. Resistance was lost slowly until early April and rapidly thereafter. In general, each nitrogen and carbohydrate fraction increased in content during the fall, was at its highest level sometime during the fall or winter, and then decreased during the spring. Correlation coefficients of the trends of the chemical fractions with the trend of cold resistance were significant in many cases.

Growth responses of smooth bromegrass (Bromus inermisLeyss), Kentucky‐31 tall fescue (Festuca elatiorL.), and common Kentucky bluegrass (Poa pratensisL.) to the growth‐regulating chemicals F‐529 (N‐pyrrolidinosuccinamic acid) and Cycocel (2‐chloroethyltrimethylammonium chloride) were studied. Growth of grasses was reduced to near zero when Cycocel was applied at a concentration of 0.584M, with at least some retardation occurring up to 100 days after application. F‐529 was less effective than Cycocel in retarding grass growth. Maximum reduction occurred at the 0.45Mconcentration where growth was reduced to 35% of the control, and at 70 days following application there was no reduction. Recovery from both chemicals was generally followed by a period of stimulated growth. Water use, in general, was highly correlated with amount of top growth. Food reserves of plants as determined by eiolated growth were significantly reduced only at the 0.292Mand 0.584Mconcentrations of Cycocel, where severe foliar damage had occurred.

Cold resistance development and maintenance by orchardgrass, as measured by indirect methods, was affected to a limited extent by cutting management and levels of nitrogen fertilization. Orchardgrass cut in early bloom was generally more cold resistant than grass cut earlier. Significant negative correlations were obtained between the percentages of the total electrolyte content exosmosed from frozen stubble on 11 fall, winter, and spring sampling dates and the concentrations of potassium, sodium, and calcium in the plant sap.

Yields increased and digestibility decreased with advance in maturity. Nitrogen fertilization influenced yields markedly but had only a minor effect on digestibility of dry matter. Amino acid levels were altered by both cutting management and nitrogen fertilization. Prussic acid levels for all treatments were low and considered as safe for livestock.

Digestibility and intake data were determined on chopped, green sudangrass fed at various stages of maturity to sheep. Feeding value, as expressed by a calculated Nutritive Value Index, was found to decrease markedly with growth stage; higher levels of nitrogen fertilization had little effect on intake or dry matter digestibility, but increased protein digestibility. In vitro indices of cellulose digestibility and gas production were found to be highly correlated with the animal criteria of digestibility, intake, and N.V.

A study to determine the extent to which winter injury of cool‐season grasses was related to genetic variation in cold tolerance, nitrogen fertilization, or previous spring and summer clipping treatments was completed at Rock Springs, Pennsylvania. Visual estimates of the percentage of winter injury sustained during the winter of 1971–72 were made in mid‐May. The grasses received 0, 60, 120, or 240 kg N/ha in spring and summer of 1971 and spring 1972. Half the plots at each rate of N were clipped at vegetative growth stages in spring, and in early June, late July, and early October. The other half were clipped after head emergence in spring, and in late August and early October. Average winter injury ranged from less than 1% for reed canary‐grass (Phalaris arundinaceaL.) to 83% for two perennial ryegrass (Lolium perenne.L.) cultivars. Kentucky blue‐grass (Poa pratensisL.) and smooth bromegrass (Bromus inermisLeyss.) were injured slightly (2 to 8%) more than reed canarygrass, and timothy (Phleum pratenseL.) and redtop (Agrostis albaL.) sustained even more winter injury (12 to 18%). Average winter injury ranged from 14 to 57% for orchardgrass (Dactylis glomerataL.), 20 to 48% for tall fescue (Festuca arundinaceaSchreb.) and 33 to 83% for perennial ryegrass. Nitrogen fertilization decreased winter survival of orchardgrass, tall fescue, and perennial ryegrass to a greater extent than it did other species. Kentucky bluegrass, smooth bromegrass, and reed canarygrass were not severely injured by either clipping regime. One or more cultivars of orchardgrass, timothy, tall fescue, perennial ryegrass, and redtop sustained winter injury when clipped at immature growth stages but were not injured when clipped at mature growth stages. Differential injury associated with the clipping regimes increased as rate of N increased. The large differences in winter injury among cultivars of orchardgrass, tall fescue, and perennial ryegrass suggest that tolerances to environmental stresses ought to be more thoroughly tested if we are to use new cultivars most effectively.