Leaf formation of successive tillers was examined with orchardgrass shoots which were developing under sward conditions. The results are summarized as follows. 1) In a sward, the leaf expansion on successive tillers of orchardgrass shoots was multifariously disturbed, and greater part of tillers expanded fewer leaves (Table 2, Fig.1, 2) in contrast with the theoretical value based on the tillering regularity in young normal seedlings which were growing seperately in favorable condition. 2) Above mentioned disturbance of leaf formation was most conspicuous during reproductive growth (from early spring to 1st cut at ear emergence) and growth suppression in hot summar, when regular leaf appearance was rarely observed. 3) As tiller bud elongation was relatively stimulated in autumn, leaf formation advanced rather regularly on each successive tiller, so that a good many of Tn-3, Tn-4, Tn-5 etc. expanded 1st, 2nd, 3rd, etc. leaf, respectively, as same as tillers in normal seedlings mentioned earlier. Neverthless, quite a few of tillers formed during this cool season expanded fewer leaves which were usually shorter than corresponding ones of mother shoot, as compared with theoretical values (Fig.3). 4) Consequently, many types of disterbance of tillering regularity in swards would be merely an effect which is caused by various suppressions of first elongation of tiller buds formed at the upper node of dominantly growing mother shoot.

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Formation of tiller buds and leaf development in dormant tiller buds were studied anatomically with orchardgrass shoots which were growing under sward conditions. The results are summarized as follows. 1) In swards, the "phase of tiller bud formation" of orchardgrass shoots proceeded almost similarly as in normally tillering seedlings, e.g. the bud primordium usually bulged out when 3〜4 leaves immediately above it were developing like a collar or more surrounding or covering over the mother shoot apex, and it developed quickly to the tiller bud being organized with its own apex and 3〜4 juvenile leaves (Fig.1, 2). This structure as a bud may be generally achieved at the uppermost leaf "n" of mother shoot. 2) The most of tiller buds formed by way of above mentioned process, however, did not reveal any analogous growth with corresponding leaf of mother shoot in most cases, because their first leaves ceased further elongation for tillering after the bud completion (Fig.2). In these dormant tiller buds, several scaly leaves lay one upon another covering collar- and hood-like leaves. This fact suggests that the exponential growth of juvenile leaves is suppresed after they have attained hood-like size (Fig.3, 4). 3) The synchronous differentiation of the corresponding leaves was observed among such upper dormant buds as Tn-1〜Tn-3 or Tn-4 in most seasons, excluding those harvested in early reproductive stage (Table 1). 4) In successively lower tiller buds inserting below than Tn-3 or Tn-4, leaf differentiation at apical region did not occur anymore, and existing leaves, especially more aged ones, decayed progressively, causing complete death of older buds (Fig.3). Thus, the dormancy of tiller buds in orchardgrass is much different from that of seeds or winter buds of trees, so that it is better to recognize it as a first step for dying.

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This study was carried out to reveal the mechanism of frost heaving injury of alfalfa which prevailed in pastures of eastern Hokkaido, Japan. For this purpose, frost heaving and alfalfa injury due to heaving were observed during two winters. Frost heaving progressed under the condition where sub-surface soil temperature was maintained around the freezing point and abundant moisture was accumulated in the soil. The amount of heaving was not correlated to freezing soil depth but to duration of such a condition which was in favour to heaving. The mechanism of frost heaving injury of alfalfa was classified into three cases based on its extent of damage. The degree of resistance to heaving injury was apparently related to the plant type, eventually to the cultivar.

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Effects of the growing environment, plant age, strains of rhizobium, and species of host plants on relative efficiency of N_2-fixation by tropical pasture legumes were investigated. Relative effeciency of N_2-fixation (RE) was computed by ; [numerical formula]. Results: 1. Rates of H_2-evolution decreased 40 minutes after the start of incubation of the legume root system in a plastic container whereas rates of acetylene reduction were not influenced. 2. RE has shown a diurnal pattern of fluctuation, being lower values during the periods of higher photosynthetically active radiation. This fluctuation was attributed to the diurnal fluctuation of acetylen reduction and H_2-evolution by the legumes. 3. RE's by several legume/strain of rhizobium combinations fell into 40〜60% except for a few instances. A definite pattern in the effects of plant age on RE was not recognized. 4. RE's by Macroptilium atropurpureum cv. Siratro inoculated with five different strains of rhizobiumm fell into 80〜90% and higher dry matter was produced in the plant having higher RE's. 5. Several host plants inoculated with a strain of rhizobium have shown different values of RE each other. With the results above, screening rhizobium for efficient strains regarding RE were recognized to be necessary for increasing dry matter production of tropical pasture legumes. However, the target plant and soil properties of the target area of the cropping should be identified before rhizobium screening.

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To evaluate the potential of the tropical pasture legumes for increasing pasture productivity in South-Western Islands of Japan, dry matter production of four tropical legumes grown in pure or in mixture with rhodes grass were compared each other or with pure rhodes grass applicated with four levels of N fertilizer under two plant heights at clipping during two years. The legume species used in the experiment are ; Macro ptilium atropurpureum cv. Siratro, Glycine wightii cv. Cooper, Desmodium intortum cv. Greenleaf and Stylosanthes humilis cv. Townsville. Siratro out-yielded other legumes and have shown better persistency either in pure or in mixtue stands indicating greater potential for pasture use in South-Western Islands of Japan. Townsville also have shown greater dry matter yield in the first year but disappeared from pasture in the second year suggesting that perennial Stylosanthes spp. might be promised in these area. Greater potentials of Siratro and the first year's Townsville were also proved with the data analysis which have shown increased productivity of these species even during hot and dry seasons.

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In order to make clear the processes of seed production of Green panic (Panicum maximum var. trichoglume) and Kazungula setaria (Setaria anceps Stapf cv. Kazungula), the differentiation stages of inflorescence and floret, processes of heading on the tillers developed at different times were investigated. The results are summarized as follows: 1) The times of the inflorescence differentiation were differed when the seeds of those both species were sown on the same date. The differentiation stages of the inflorescence on the tillers which headed at the peak of heading (in Green panic, tillers developed during the period before nine leaf stage of the main stem, and in Kazungula setaria, before fifteen leaf stage of the main stem) were ten leaf stage of the main stem in Green panic and fifteen leaf stage of the main stem in Kazungula setaria, but the differentiation stages of the floret were expanding stage of flag leaf of the main stem in both species. 2) When the main stem of those both species reached to the ripening stage, in Green panic, the most of the individual tillers which headed at the peak of heading showed a narrow range in deviations of the stage of inflorescence development and almost reached to flowering stage. In Kazungula setaria, however, those showed wide range in deviations of the stage of inflorescence development. Therefore, in the latter, the stage of inflorescence development on the individual tillers which headed at the peak of heading and on the individual tillers developed later than the tillers which headed at the peak of heading was overlapped. 3) From these results, the most important stage for the seed production was from ten leaf stage till expanding stage of flag leaf of the main stem in Green panic and from fifteen leaf stage till expanding stage of flag leaf of the main stem in Kazungula setaria. The period of those two stages was about twelve days in the former and about fifteen days in the latter.

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In order to make clear the effect of temperature on the development of inflorescence, heading and seed yield in Green panic (Panicum maximum var. trichoglume) and Kazungula setaria (Setaria anceps STAPF cv. Kazungula) an experiment was conducted in a phytotron under three constant temperature regimes of 20℃, 25℃ and 30℃ through day and night. The results were as follows: 1) In Green panic, the stage of inflorescence development was more advanced at 25℃ than other two temperature regimes and when the inflorescence development of main stem reached to ripening stage, the deviations among the investigated tillers showed a narrow range. While in Kazungula setaria, the stage of the inflorescence development reached almost to the same stage under each temperature conditions, but the diviations among the investigated tillers showed wider range at 30℃ than other two temperature regimes. 2) Total numbers of heading tillers of those two species were maximal at 25℃, being following by 20℃ and 30℃. 3) The seed weight per head of those two species was highest at 25℃, but was lowest at 30℃ in Green panic and 20℃ in Kazungula setaria resulting about the half of seed weight at 25℃. These results show that the development of inflorescence, heading and seed yield in those two species were most effective at 25℃. In Green panic, however, it was recognized that under the high temperature (30℃) the development of inflorescence was delayed, head size was smaller, and filled seeds and seed weight per head were extremely decreased. While in Kazungula setaria, it was recognized that the development of inflorescence was not affected by temperature conditions, but the head size was largest under the low temperature condition (20℃).

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In the previous paper, it was suggested in orchardgrass that the low temperature and short-day requirement for floral-induction become lower with the advance of plant-age after the juvenile stage. The study reported here was carried out to clarify the effective range of temperature and day-length on floral-induction in aged plants. Clonal plants of "Aonami", "Latar", "Aberystwyth S143" and "EV-700" were grown under continuous light in a warm (25℃ day/15℃ night) glasshouse for longer than 6 months before being separated into individual tillers, from which aged tillers were chosen for the experiments. Then, the tillers were subjected to floral-induction treatment of outdoor- or unheated glasshouse-temperatures with natural day-lengths for five weeks. The experiments were conducted with intervals of 2-month from October, 1976 to August, 1977 (Fig.1 and Table 2). After the treatments, they were retransferred to a warm glasshouse under continuous light, and their heading behaviour was observed. Floral-induction was promoted in the range of mean temperature from 5.3 to 15.8℃ in "Aberystwyth S143" and 5.3 to 19.0℃ in "Aonami" and "Latar", and retarded when mean temperature was higher than those ranges described above in these three materials. While the whole range of mean temperature used in this study (5.3 to 22.9℃) was effective on floral-induction in "EV-700". Day-length changed seasonally from the minimum of 9hr., 37min. to the maximum of 14hr., 43min. This range of day-length was shorter than the critical day-length for floral-induction in all the materials tested (Table 3). As the day-length during floral-induction treatments became longer, the number of days from the beginning of treatment to heading became smaller (Table 4). From the results of the treatment in "June" during which day-lengths were longer than 14hr., 32min. and temperatures were moderately high (mean temperature ; 19.0℃), it was estimated that 15.2, 21.8, 21.3 and 11.5 days were required for floral-induction in "Aonami", "Latar", "Aberystwyth S143" and "EV-700", respectively (Table 5 and Fig.2). These estimated values suggested that, in aged plants, the period required for floral-induction under fairly long day-length and high temperature was almost similar to that under short day-length and low temperature. From the above results, it may be concluded that the effective range of temperature and day-length on floral-induction is markedly wider in aged plants than in seedlings.

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The seasonal changes of leaf growth from the onset of leaf expansion in early spring to heading and its adaptive significance were studied in natural populations of timothy (Phleum pratense L.). Seeds were collected from 12 locations in northern area (northern group) and 16 locations in southern area (southern group) of Hokkaido (Fig.1) and sown in field at Sapporo. In the second year after seeding, the most vigorous tiller on each plant was selected on May 2, and the number, length and width of successively expanded leaves on the tiller were measured on May 16 (early growing stage), June 5 (middle growing stage) and after heading (late growing stage), respectively. Based on these measurements leaf area expansion per tiller was determined as the sum of sizes (length×width) of fully expanded leaves in each growing stage. The southern group had larger leaf area expansion than the northern group in the early growing stage (Table 1, Fig.2). It was true for leaf length in early and middle growing stages and leaf width in the early growing stage. In the late growing stage the northern group had larger leaf number than the southern group. However, there was no difference in leaf area expansion summed over three growing stages. The variance ratio σ_B^2/(σ_B^2+σ_W^2) for leaf area expansion was higher in the early growing stage than in the middle or late one (Fig.4), where σ_B^2 and σ_W^2 are the variances due to between and within groups, respectively. Heritability of leaf area expansion in the early growing stage was also high (Fig.3). It was suggested by this result that these two groups differed from each other in the leaf growth type well adapted under low temperature conditions in early spring. Leaf area expansion in the early growing stage was positively correlated with monthly mean temperature in winter at the collection site (Fig.5). It was pointed out from these results that northern populations inhibited leaf growth under relatively low temperature conditions and increased cold tolerance, and thereby adapted to the unpredictable climatic fluctuations in early spring peculiar to the northern area of Hokkaido.

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This experiment was conducted to clarify the effect of nitrogen fertilization on yield and in vitro dry matter digestibility (DMD) of fall-sown cereal crops for silage. Six-rowed barley, two-rowed barley, naked barley, wheat and rye were cultivated at various nitrogen levels for three years. One cultivar was used for each crop. In a fertile and well-drained field, herbage showed the ceiling yield in dry matter (DM) at about 15kg nitrogen application per 10 ares. In a drained paddy field after rice culture, the ceiling yield in DM would be obtained more than 17kg N/10a. Applied nitrogen decreased the proportion of stem and ear in DM yield and increased that of leaf. It did not change DMD of most of plant parts and whole plants or it slightly decreased DMD of them. The relation between applied nitrogen amount and DMD of a whole plant was parallel to the relation between applied nitrogen amount and DMD of stem, because stem was the largest of three parts of a plant. On the assumption that the digestibility of cellular content (CC) is constant, a change in DMD of each plant part by the nitrogen application was mainly attributed to a change in estimated digestibility of cell wall constituent (CWC) in each plant part. Nitrogen application did not consistently change the ratio of CC to CWC of plant parts except stem, and a change of the ratio in stem by applied nitrogen showed a little effect on a change in DMD of stem. A change in estimated cell wall digestibility of leaf and ear by applied nitrogen was correlated with a change in acid detergent lignin in CWC. Nitrogen application increased the digestible DM yield and this increase depended on that of DM yield. Ceiling yield of digestible DM was obtained at the same nitrogen level that gave the ceiling yield in DM. Five cultivars were not different from each other in the response of DM yield and DMD to nitrogen application.

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Our previous study was intended to estimate the grazing intake of steers on the native pasture by chromogen-chromic oxide method. The results of the study showed that the recovery rate of chromogen was abnormally low in autumn in spite of the satisfactory rate in spring and that the estimation of grazing intake on the native pasture in autumn by this method was therefore practically impossible. Thus it was assumed that the low recovery rate of chromogen might be attributed to the leaf senescence of the native grass grazed in autumn. In this study, therefore, the recovery rates of chromogen were measured using sheep fed on Miscanthus sinensis of different growth stage through the seasons in 1976 and 1978. The results obtained were as follows: The concentration of chromogen and its recovery rate were satisfactory for each grass fed in spring and summer. As for the grass fed in autumn, the concentration in 1978 and the recovery rate in 1976 were extremely low. From this results it was presumed that the chromogenic substances in autumn grass became unstable at first and then decreased later according to the stage of aging. Namely autumn grass fed in 1978 reached such a late stage that the most of chromogenic substances had disappeared, whereas the one fed in 1976 still remained in an early stage and preserved the unstable chromogenic substances which might be decomposed and absorbed while passing through the digestive organ of animal.

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The fibrous residue left after the extraction of leaf protein from broad bean (Vicia faba L.) was ensiled, and its food value was examined in digestion and nitrogen balance trials using sheep fed only the silage at 2.0% level of dry matter per kg body weight. The results obtained as follows ; 1. The digestibilities of organic matter, crude fat and NFE were significantly higher in silage feeding than in feeding of timothy hay as a control ration. The digestibility of crude protein, howevre, was significantly lower in silage feeding. 2. The urinary nitrogen excretion was high in silage feeding compared with that in hay feeding, and it was reduced in the feeding of silage plus hay (1:1/D.M.). As a whole, the retained nitrogen was similar in both feedings of silage and silage plus hay. Consequently, the net utilization of dietary nitrogen was the highest in silage plus hay feeding. 3. The concentrations of ruminal ammonia and VFAs were higher in silage feeding than in feeding of hay with or without silage. This might show a high ruminal fermentation after the silage feeding in sheep. 4. The blood glucose level was almost similar in both feedings of silage and hay. The concentration of plasma total protein was similar in all feedings of silage, hay and silage plus hay. The level of blood urea-nitrogen was higher after silage feeding than after hay or silage plus hay feedings. From the results described above, it is concluded that the silage made from a fibrous residue of broad bean, when used as roughage by sheep was some what superior in food value to timothy hay, and it is also suggested that nitrogen utilization of the silage may be efficiently improved by using hay jointly at the same time.

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The adverse effects of coll summer were estimated in terms of lost nutritive values and yield reductions in corn silages made from the crops grown in 1980 in Tokachi district. the tests were carried out on three varieties of different maturity (early, medium, late), planted on two different dates (12/5, 3/6). The results obtained were summarized as follows. (1) Meteorological records indicated abnormal low air temperatures from July through August, throughout the eastern Hokkaido, with the mean air temperature at 3.6℃ lower than the level of normal years. (2) The crops were harvested on September 24th. The degree of maturity at the time of harvest of the early variety had reached the late yellow dent stage, both the medium variety and the early one which was sown late the early dough to early yellow dent stage, and the late variety the milk stage, respectively. Generally speaking, maturation processes were very much retarded when compared to the level attained in normal crop years, with the exception of the early variety sown on the standard date. (3) The starch content of the silage of each variety was lower than the level of norml crop years, while the contents of moisture and acid detergent fiber (ADF) showed a tendency to increase. Consequently, the quality of silage, as jugded by chemical scores, was inferrior to that obtained for the corresponding sample of normal crop years. (4) The digestible starch contents of all silages were very much lower than those of normal crop years, with the yield reduction of some where between 40% and 70%. However there was no significant difference in the total digestible nutrients (TDN) contents between the crop years examined. The digestible crude protein (DCP) contents showed a tendency to surpass the level of normal crop years. (5) Nutrients yield of the early variety of standard sowing date reached the level of normal crop years, while that of both medium and late varieties of the same sowing date fell short of the normal level by 8% to 15%. Delayed sowing date further resulted in marked reduction of yields. We conclude that the use of early varieties as well as the practice of early sowing is highly desirable with the aim to minimize the adverse effects of occasional cool summer seasons.

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In order to find the simple method for evaluation of nutritive value of rice straw, the dry matter digestibility of rice straw by the method of artificial rumen was discussed for the digestibility, composition, and the intakes by wethers under the feeding condition of wheat bran 400g per head daily and rice straw of full ripe stage (7 samples) and tillering stage (4 samples) ad lib. The results were as follows: 1) Correlation between in vitro dry matter digestibility and in vivo digestibility of each compositions is low and not significant. 2) Correlations between in vitro dry matter digestibility and the amount of in vitro digestion of each compositions per W^<0.75> were positive, and crude protein (P<0.01), dry matter, and energy (P<0.05) were significant. 3) The compositions showed significant correlation (P<0.01) between in vitro dry matter digestibility and composition of tested straw (combined full ripe stage with tillering stage) were crude protein (r=0.843), NDF minus ADF fraction (r=0.744), lignin plus crude silica (r=-0.792), and crude silica (r=-0.723). 4) Correlation between intake of tested straw per W^<0.75> and in vitro digestibility was almost undiscernible. 5) Compositions of tested straw affected on in vitro dry matter digestibility and dry matter intake per W^<0.75> in the same manner, because these factors showed similar correlation each other. 6) Therefore, the evaluation of nutritive value of tested straw by the method of artificial rumen is possible, and also from the contents of NDF minus ADF fraction, crude protein, lignin plus crude silica, and crude silica alone, the nutritive value of tested straw could be estimated.

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As a part of microbiological studies on nitrate disappearance, the culture conditions for the growth of nitrate reducing bacteria in silages were investigated. In this paper, effect of the medium added with the water extract of the silage on the growth of nitrate reducing bacteria was espeically studied. The results obtained were as follows: 1. The composition of basal medium was 0.5% meat extract, 0.5% polypepton and 0.1% KNO_3 with an initial pH value of 7.0. The numbers of nitrate reducing bacteria increased at 28℃ for 3 days culture in the medium added with 5% water extract of silage, but further increase in added water extract of silage did not affect on the growth of bacteria. 2. The growth of bacteria was promoted by increasing level of added KNO_3. 3. The optimum pH and temperature for the growth were 7.0 to 7.9 and 28℃, respectively. There were no marked difference in the growth of bacteria among stationary culture, stationary culture after the shaking culture for 6hr and stationary culture covered with fluid parafin.

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