To screen orchardgrass plants for digestibility, the authors simplified the two step cellulase method recommend by ABE et al. (Jap. J. Zootech. Sci., 43: 175-180). The simplified one-step cellulase method is as follows: a sample of 0.5g is incubated at 40℃ for 6 hours with ca. 45ml of 1% cellulase solution in a 50ml polyethylene tube placed in a shaking apparatus. Cellulase is dissolved in acetate buffer solution adjusted to pH 4.0. After incubation, the solution is filtered with No.5A filter paper and the residue is dried and weighed. Digestibility values analysed by this method are lower than those in vivo (Table 2). When 11 samples with high and low digestibility standards were artificially mixed and then analysed by the one-step cellulase method, the correlation coefficient with calculated in vivo digestibility was significant (r=.996, Fig. 1). Furthermore, when three standard samples were analysed 14 times, standard errors were low (.26-.30%, Table 2). It is concluded that the one-step cellulase method is very useful for screening orchardgrass plants. Using this technique, digestibility of 7 synthetic strains and a variety (n=64 plants each) was estimated for 2nd cut hay. Strain difference between highest and lowest digestibility was only 2.4%, however, the difference was highly significant. Range of digestibility for 511 orchardgrass plants (one sample was lost) was 14.9% (Table 3). Characteristics of the 511 orchardgrass plants were investigated for vigor, diseases, growth habit, leafiness, date of heading, and panicle number (Table 1). Means of digestibility for plants which belonged to the same character ranking were calculated. Significant differences were obtained among ranks for growth habit (1st cut), vigor (1st cut) and diseases (1st cut, 2nd cut, and fall, mainly scald caused by Rhynchosporium, Table 4). Especially in growth habit and diseases of 2nd cut, trends were observed. Digestibility of prostrate-type plants was lower than that of erect- and mid-type ones. Furthermore, plants susceptible to the diseases showed low digestibility.

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In order to establish proper method of harvesting seed of Kazungula setaria (Setaria anceps cv. Kazungula), an experiment was conducted to clear the processes of the heading and seed ripening in this grass. The results obtained are as follows. 1) The maximum rate of heading was observed at about 4 weeks after the heading began, and before this time large sized heads almost emerged (Fig.1). 2) The blooming of florets occured at night ; starting from 11:30 p.m. and most frequently until 1:30 a.m. (Fig.2). The blooming started from the florets located at about one-third length lower than the tip of a head and it proceeded towards both ends. The blooming was kept up for about 10 days per head, and lasted for 2 or 3 hours per floret. 3) On the 18th day after the blooming started in a head, the shattering of florets was first observed. The maximum percentage of viable seeds and pure germinated seeds per head could be gained at the time when the shattering started (Fig.4). 4) Seeds thinner than 0.40mm were not able to germinate, and in case of seeds thicker than 0.41mm, the thicker seeds showed the higher rate and percentage of germination (Fig.5) These results could suggest that when the seed crop is harvested from a group of large-sized heads which constitute the first maximum rate of heading and when harvested as soon as the shattering started, the highest seed yield of good quality will be obtained.

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With an aim to clarify the relationships of morphological and physiological characters of Silphium to day length, the experiments were conducted at the Akita Agricultural College during three years from 1974 to 1976. The results obtained were summarised as follows: 1. In the middle of August, the plant hight, leaf area, top-weight and root length under natural day length showed no significant difference from those under long day length with a few exceptions. These exceptions were (1) the values of the leaf area and the top-weight in the seeding year under natural day length were higher than those of plants grown under long day length, and (2) the values of the weight of underground parts in the third year after seeding under long day length were higher than that of plants grown under natural day length. Under short day treatment, the values of these characters were significantly small. However, in the middle of November, these characters showed higher values under long day treatment than under the natural day length. 2. As to the numbers of leaves and stems and the thickness of stem in the middle of August, there was no difference among the treatments of day length, but in the middle of November, the numbers of leaves and stems under long day length exceeded them under natural day length. 3. Elongation of the basal internode of stems did not occur in the year of establishment, which was almost same with the internodes of plant grown under eleven hour day length in the second and third year. The elongation of internode of plants grown under the long day length and the natural day length was found in the second and third year. And, it is assumed that the elongation of basal internode will necessitate fundamentally at least fifteen or sixteen leaves. 4. The long day length over natural day length appeared not to be effective to the bud formation, and the short day length of eleven hours was found to suppress bud formation almost completely. Also, the flowering of bud did not occur under the short day length in general. Plants grown under the long day length and natural day length treatments reached to flower at the same period. From these, Silphium was regarded as a quantitative long day plant. 5 Any difference of T/R ratio could not be found between natural day length and long day length and long day length treatments in the middle of August, but the ratio in the short day treatments was clearly lower than that of the former two. As the seedling stage was progressed, T/R ratio became lower. On the other hand, in the middle of November, T/R ratio in long day length was higher than in natural day length. In consequence, it was supposed that such vigorous growth of underground parts under long day length will result in the desirable top growth in the following spring. 6. The long day treatment gave no special effect on the seed production. On the contrary, short day treatment was found to suppress greatly its production.

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The effect of density in the late seeding culture of Sorghum, seeded in middle or late June, harvested in late August, on the yield of Sorghum crop for silage, and on number of stems were studied by investigation of variation of stems. 1) The yield and number of stems increased with increase of density. In the highest-density-plot, the number of stems per area was very high. 2) Main stem seldom die, therefor the ratio of number of stems per plant at harvest to that at maximum tiller number stage was high in the low-density-plot and also in the highest-density-plot, where few tillers were produced. 3) A group of small stems, low height and high ratio of leaf weight to top weight, is distinguished from group of general stem, cansisting community. The group of small stems seems to be established by the stem which remained in the leaf canopy. 4) Generally, the higher the density is, the higher the ratio of small stem is. But, the ratio of small stem was low in the highest-density-plot, because the ratio of main stem was high in the plot, and main stem seldom becomes small stem.

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In order to make clear the varietal differences in the growth response to temperature of Italian ryegrass, five varieties and three strains were grown under four different temperatures i.e. natural outdoor temperature of late fall and 15℃, 20℃ and 25℃ by means of phytotron for 30 days from the two-leaf stage of seedlings main stem. Growth analysis and quantitative chemical analysis of water soluble carbohydrate (WSC) and total nitrogen (T-N) of the plant material were carried out. Differences in some morphological and physiological characteristics between diploid (2n) and tetraploid (4n), and between low (Ls) and high (Hs) snow endurance varieties and strains were also studied. 1) Italian ryegrass at the four-to six-leaf stage grown outdoor could be classified roughly into two groups according to the differences in the growth response to the low temperature in fall. Comparing to the NAR and RLGR at 10 to 20 days, one group showed more rapid decrease in NAR and increase in RLGR at 20 to 30 days when the natural daily mean temperatures went down to about 8℃. And in the same periods, the other showed slight increase in NAR and decrease in RLGR. RGR was higher in the latter than in former. The former and the latter correspond to the early and late varieties and strains respectively within the limit of this experiment. 2) Highly significant correlations between RGR and NAR were obtained under each temperature treatment in phytotron. And it was clearly recognized that those varieties and strains which showed relatively good low-and high-temperature growth had higher ability of keeping the same level of NAR under the low and high temperatures as under the optimal temperature. 3) Variation in the dry matter percentage in the stem, in the water solublule carbohydrate percentage, and in the total nitrogen percentage of stem and leaf among varieties or strains was greater in the order of 25℃, 20℃, 15℃, natural temperature outdoor. High correlation coefficients among these values were obtained at natural temperature outdoor and 15℃, on the contrary, low or nearly no correlations were obtained at 20℃ and 25℃. 4) It was confirmed that when the SLA values of 2n and 4n were equal, 2n showed higher NAR than 4n, and that when the dry matter percentages in the stem of 2n and 4n at low temperatures were equal, 4n showed higher WSC and lower T-N percentages of the stem than 2n. 5) Dry matter percentage in the stem at 30 days under 20°and 25℃ was lower in 4n than in 2n, on the contrary, no clear difference was obtained at natural temperature outdoor and 15℃. 6) The Hs varieties and strains regardless of 2n or 4n, had relatively higher values of NAR with lower SLA and LWR values under each temperature treatment. It was also confirmed that the Hs varieties and strains had higher drymatter percentages in the stem, and higher WSC and lower T-N percentages of leaf and stem under natural temperature outdoor and 15℃. 7) It is suggested that the level of dry matter percentage and WSC percentage of stem of young plant at the five-to six-leaf stage grown under low temperature may be useful as an index of snow endurance.

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1. The yearly and seasonal productivities in orchardgrass swards of several locations (Sapporo 43°03'N, Nagano 36°40'N, Kumamoto 32°49'N) of Japan were compared climatically in relation to elevation, slope inclination and exposure of sward. The mean crop growth rates (C^^^) during the growing period above monthly mean air temperature 5℃ were calculated from the formula and the data presented in the previous papers (VII and XI) on the basis of two climatic factors, solar radiation and air temperature. And the C^^^ was discussed in this paper as the climatic productivity. 2. The favorable positions for the yearly climatic productivity (C^^^_y, yearly mean value of C^^^) moved from the low up to the high elevation with the lowering of latitude, and the growing periods above 5℃ and the warmth indices in those positions were 214-244 days (7-8 months) and 65-80℃. month, respectively (Figs.1 and 2). Therefore, it may be considered that these values are available as the indicators to predict the climatically favorable zone for the sward production of orchardgrass in Japan. 3. The yearly climatic productivity (C^^^_y) changed with the exposure and the inclination of sward, and in general, the lower C^^^_y was showed in the northern side slope and the higher C^^^_y was showed in the southern side slope as compared with the eastern and western side slopes. C^^^_y in the northern side slope decreased remarkably with the increasing of inclination of sward, but C^^^_y in the southern side slope increased slightly with the increasing of inclination from 0° up to 20°. The changes of C^^^_y according to inclination of sward were not conspicuous in both side slopes of the eastern and western (Fig.1) 4. The seasonal curves of monthly climatic productivity (C^^^_m, monthly mean value of C^^^) of sward varied from mono-peak type (with early summer's peak) to two-peak type (with spring and autumn's peaks) in accordance with the positional changing of sward from the high down to the low latitude and also from the high to the low elevation (Fig.3). 5. The sward production in the autumn season showed the increasing trend with the changing of exposure from the northern to the southern side slope and this trend was enhanced by the increase of slope inclination of sward (Figs.4 and 5).

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1. The regional characteristics of the productivity of orchardgrass sward in Japan were discussed in this paper from the viewpoint of climatic conditions. The climatic productivities (C^^^_m, g/m^2\day) of orchardgrass sward were calculated by the same method used in the previous paper XIII and were presented in the Table 1. The C^^^_m in each location was estimated from the Table 1 on the base of each location's monthly solar radiation and air temperature. According to the Table 1, the maximum C^^^_m (C^^^_<max>) was shown at 16℃ (optimum air temperature), and the reductions of C^^^_m were shown at unfavorable air temperatures above and below 16℃. And also it was made clear that the increase of solar radiation acted positively to C^^^_m at any air temperatures. 2. The reductions of productivity caused by unfavorable air temperatures above and below 16℃ were able to be indicated as the difference between C^^^_<max> (productivity of solar radiation at the optimum air temperature 16℃) and C^^^_m (productivity of solar radiation at the actual air temperature). Both values of the period and the amount of decrease of C^^^_m caused by high air temperature showed a increasing trend with the lowering of latitude and elevation. On the contrary, those of C^^^_m caused by low air temperature showed a increasing trend with the ascending of latitude and elevation (Figs.1 and 2). 3. The yearly amounts of maximum climatic production (C^^^_<max>×days) and of climatic production (C^^^_m×days) showed the increasing trends with the changing of position from high down to low latitude (Fig.6), but the ratios of the yearly amount of C^^^_m to that of C^^^_<max> were almost constant in the different latitudes (Fig.5). 4. The ratio of decrease amount of production caused by high air temperature showed the increasing trends with the lowering of elevation and latitude, and had high significant correlations to the high-temperature index (Fig.3). On the other hand, the ratio of decrease amount of production caused by low air temperature increased with the ascending of elevation and latitude, and showed high significant correlations with the low-temperature index (Fig.4).

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The six cool temperate grasses had been grown under mimic grazing system for 6 years on field plots treated with two levels (N-P_2O_5-K_2O: 1-1-1 and 4-4-4kg/a/year) of fertilizer supply respectively. Chemical analyses of macroelement were made for the samples obtained from each cut of the above trial and analytical data were examined in relation to occurrence of summer depression using statistical method. The main findings were as follows: 1) Yearly or seasonal fluctuation of macroelement content in herbage showed that N, P, Ca and Mg were related to occurence of summer depression. Therefore, taking into account the effect of these elements on the development of root, it was possible to suggest a definition of root value as follows: [N/P×1/(Ca+Mg)% ratio] of top. 2) Close relation was recognized between occurrence of summer depression and root value of each species in spring. Increases in the value tended to accelerate its occurrence in case of all species. The extent to which each species was affected by the root value decreased in the order as follows : perennial ryegrass>orchardgrass>tall fescue>Kentucky bluegrass>red top Above tendency well reflected the susceptibility to summer depression of each species. 3) Investigating each effect of N/P and 1/(Ca+Mg) which were obtained by separating the root value into two parts, it was found that concerning summer depression, orchardgrass and perennial ryegrass were remarkably susceptible to N excess or P defficiency and soil acidity most severely affected perennial ryegrass which was followed by tall fescue in severity. 4) The occurrence of summer depression was closely related to both root value and meteorological factors such as precipitation during rainy season and temperature in July. The equations which indicated the relation between above factors showed that severity of summer depression varied markedly due to difference of soil fertility even under similar meteorological condition and orchardgrass and perennial ryegrass were much more susceptible to both factors than the other species were. It was concluded that additional application of P, Ca, and Mg should be done based on meteorological factors for longer and more efficient utilization of grassland where cool temperate grasses were dominant under such specific condition as Japan located in the monsoon zone in which P deficient and acidic, volcanic 'ash soils were widely distributed.

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As a part of studies on forage roots and physical properties of grassland soil, the present experiment was conducted to investigate an effect of growth of grass roots on soil structure at plow layer. The soil used was KUROBOKU-soil, and experimental plants were timothy and upland rice. The results are summarized as follows ; (1) The forage roots concentrated in the layer from 0 to 10cm, though the soils were uniformly placed in the plots. (2) The percentage of new roots in forage roots was more than 40% through the experimental period. (3) The soil-hardness and solid ratio increased remarkably at 5cm depth in the forage plot and at 15cm depth in the rice plot. The former depth was due to the influence of growth of root-system and the latter depth was derived from impact such as plowing. (4) The effective soil aggregates (>1mm) were developed with the growth of root-system in both plots. However, no relation was observed between aggregates development and roots distribution. (5) The increase of effective soil-pore (1.5<pF<2.7) was recognized at 5cm depth in the forage plot. And compared with the rice plot, total soil-pore in the grass plot was less than that in the rice plot section, but effective soil-pore in the forage plot was more abundant than that in the rice plot.

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In the present paper, as a part of studies on forage roots and physical properties of grassland soil, we deal with the growth of root-system in fixed pore model which was made of steel nets or glass beads. Four crops as Italian ryegrass, dent corn, oats and ladino clover were used in this experiment. When the roots of these crops penetrated into the pores in model culture box, their numbers, length, thickness and root-system were investigated by using a projector. The results are summarized as follows ; (1) Each root of Italian ryegrass was able to penetrate into the pores of net with 300μm meshes only. From the result of investigation on the thickness of these penetrating roots, their roots were able to penetrate into the pores of which diameter is narrower than root-diameter. (2) In the case of Italian ryegrass, as compared with the roots in culture box with small pore size (300μm and below), the roots in culture box with large pore size (300〜775μm) showed maximum value in root number and root length. However they showed minimum value in root diameter. In case of other crops, the relation among the root number, root length and root diameter could not be observed. (3) If the pore size became narrower, root-system of Italian ryegrass was effected more sensitively than in other crops. That is, root number increased and individual root became fine and crooked (see Fig.3). (4) It is considered that grass roots such as Italian ryegrass grow up transforming themselves in the culture media with fixed and narrow pores.

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The relationships between the contents of chemical constituents and their digestibility, dry matter digestibility, digestible cell wall fractions and digestible cell contents were examined using grasses grown in three different seasons. Among the contents and digestibilities of crude fiber, cell walls (CW) and acid detergent fiber (ADF), significant correlations were observed with first cutting grasses in spring, whereas, aftermath growth in summer and autumn had little correlation between them. Nonsignificant correlations were obtained between digestibility of carbohydrate and contents of the structural carbohydrate with the aftermath in summer. The contents of acid detergent lignin (ADL) and ADL+silica gave high negative correlations with digestibilities of carbohydrate and dry matter throughout the three seasons. The relationships between the contents of CW, ADF, ADL, silica, ADL+silica, ADL/ADF on the one hand and digestibility of CW and cell contents, their digestible amount, their indigestible amount on the other hand were determined. Seasonal effects on these relationships were observed.

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