The relationships between photosynthesis rate of leaves and specific leaf area (SLA) were elucidated in 50 plants from five timothy varieties. There were significantly. negative correlationships between photosynthesis rate and SLA through the growing season and the correlationship was closest (r=-0.763)in June, the heading time of timothy plants. The varietal differences existed in both the photosynthesis rate and SLA, for instance, CLIMAX was a variety showing high photosynthesis rate and low SLA, and S 51 was a variety showing low photosynthesis rate and high SLA. The timothy plants with high photosynthesis rates during the heading season had a considerably high possibility of showing high photosynthesis rates during another season. As the correlationship between photosynthesis rate and SLA became closest in the heading time (June), it was considered most effective to use SLA observed in this time as a criterion for the selection of timothy plants with high photosynthesis rates. Using 32 plants from four timothy varieties, the influences of day length on photosynthesis rate of leaves and SLA were investigated. During the mild air temperature (16℃) season (August-September) the timothy leaves grown under the long day (18 hours day length) condition showed higher photosynthesis rates than those grown under the natural day length (14 hours) condition. Contrary to this, during the cool (9.6℃) season (October-November) the photosynthesis rates were lower in the leaves grown under the long day condition. The influences of interaction of day length and air temperature on the photosynthesis rate were recognized. The values of SLA had a tendency of increasing under the long day condition at both the mild and low air temperature.

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This study was undertaken to investigate the difference between tropical and temperate grasses in photosynthetic rate. The photosynthesis and respiration of an attached leaf were measured in an assimilation chamber (Fig.1) under artificial light condition. The concentration of CO_2 gas in the air was surveyed at the point of entering and leaving of the chamber by means of infra-red gas analyzer. Fourteen temperate and 27 tropical species (including sorghums, corn and African millet) were used. Photosynthesis was measured under light intensities being kept 45 Klx. for temperate and 65 Klx. for tropical species and respiration was measured in darkness. Air temperatures were controlled at 20±0.5℃ for temperate and 35±0.5℃ for tropical species by passing a stream of warm or chilled water through a jaket of the chamber. The experiments were carried out during May in 1975 for temperate species and late June to July in 1976 for tropical species, respectively. The results obtained were summarized as follows. It was quite evident that photosynthetic rate differed sharply between tropical and temperate grasses, being lower in the latter. Most tropical grasses were able to reach about twice as much CO_2 assimilation as the temperate grasses. Especially, dallisgrass, makarikarigrass, green panic, vaseygrass, Rhodesgrass, bahiagrass and grain sorghum showed higher photosynthetic rates (50-55mg CO_2・dm^<-2>・hr^<-1>). Tropical grasses such as Saint Augustine grass, weeping lovegrass, carpetgrass and kikuyugrass, however, showed no more than 27-31mg CO_2・dm^<-2>・hr^<-1>, which value was almost similar to that of smooth bromegrass and tall fescue of temperate grass. From these results, it is suggested that not all of tropical grasses show a high CO_2 assimilation. A significant negative correlation was observed between photosynthetic rate and specific leaf area in temperate grasses and no correlation was found in tropical grasses. Tropical grasses which belong to Panicoideae or Eragrostoideae are superior in photosynthetic activity to temperate grasses of Festucoideae. It is assumed that the species of Panicum, Paspalum and Chloris are superior to the other genera of Panicoideae or Eragrostoideae in photosynthesis. Therefore, it may be concluded that these specific differences in photosynthetic activity are closely associated with taxonomic and evolutionary group of each grass species.

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The previous experiment showed that the effect of nitrogen fertilization on the early growth of some subtropical grasses differed with species. This experiment was made to clarify which was more closely related to the above-mentioned specific difference, net assimilation rate or leaf area expansion. The grasses used were Rhodesgrass (Chloris gayana KUNTH.), dallisgrass (Paspalum dilatatum POIR.) and bahiagrass (Paspalum notatum FLUGGE). Nitrogen fertilizer was applied at six levels when all species reached the fifth leaf stage and plants were harvested two weeks after the nitrogen application for the standard growth analysis. The average daily maximum and minimum temperature during the experimental period were 33.4℃ and 18.9℃, respectively. Results were summarized as follows: 1. Rhodesgrass showed the highest relative growth rate (RGR) with increase of nitrogen level, followed by dallisgrass and bahiagrass in order. N level at which RGR reached its maximum was also the highest in Rhodesgrass and the lowest in bahiagrass. 2. Such a similar specific difference as found in RGR was also shown in leaf area ratio (LAR), especially in relative leaf growth rate (RLGR), but, as for net assimilation rate (NAR), all species reached their maximum at a same low N level although Rhodesgrass showed a somewhat higher NAR value. 3. Correlation coefficients between RGR and NAR, RGR and LAR, RGR and RLGR were calculated for all species. The coefficient between RGR and RLGR showed the highest value and those between RGR and NAR showed the lowest value for all species. The results mentioned above indicated that the specific difference of the effect of nitrogen fertilization on seedling growth was more closely related to leaf area expansion than to net assimilation rate.

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Four corresponding pairs of Italian ryegrass i.e. tetraploid strains and their respective diploid parental varieties were grown at different temperatures of 15℃, 20℃ and 25℃ for 30 days after seed germination. Difference of the growth and the chemical composition between diploid and tetraploid strains were compared under different temperature conditions. 1. Plant height, weight of individual tiller, weight and area of a single leaf and specific leaf weight of tetraploids were markedly higher than those of corresponding diploids, on the other hand, number of tillers and leaves of each plant and leaf age were interior in tetraploids than in diploids at all temperatures. These results indicate that the characteristics of gigas type and lower tillering capacity in tetraploids. 2. Leaf area and weight of shoot of tetraploid strains were markedly higher at early periods of the experiment and relative value of tetraploids to diploids decreased with the advance of the developmental stage. In the later part of the experiment at 20℃ and 25℃, the growth of leaf area of diploids showed rather superior than tetraploids, suggesting the reduction of relative leaf area growth rate (RLGR) and relative growth rate (RGR) of shoot due to the induced doubling of chromosome number. 3. Reduction of RGR in tetraploids was resulted from the low leaf area ratio i.e. specific leaf area. Leaf weight ratios showed no difference between diploid and tetraploid strains. But net assimilation rates were slightly higher in tetraploids. 4. Total nitrogen percentage of leaf blade and stem showed no clear difference between ploidy levels at any temperatures, but in many cases NO_3-N percentages were lower in tetraploids than in diploids. Water soluble carbohydrate percentages of stem were markedly higher in tetraploid and relative value of tetraploids to diploids were higher at lower temperature than at higher temperature, indicating higher ability of tetraploids to store carbohydrate in the stem at low temperature. 5. The relative indices of RLGR, RGR of tetraploids differed as affected by temperature, indicating differences in growth response to the temperature between ploidy levels.

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A field experiment was conducted to study the change of the digestibility of green panic with the advance of growth and the digestibility of the aftermath, in relation to the pattern of tiller appearance. Plants were sown on May 12, 1976, and cut at 5cm from ground level at 6 stages of growth ; vegetative stage (T_1), culm elongation stage (T_2), flag leaf expanding stage (T_3) and heading stage (T_4) of the main shoot in the first growth, and 21 days regrowths after the defoliations at T_2 (T_2-2) and T_4 (T_4-2). Tillers consisting yield portion were assorted according to the appearance interval of three days. Two active-tillering stages were observed in the first growth, one was at late vegetative stage and the other was after culm elongation. In the aftermath, many tillers appeared immediately after defoliation, decreased subsequently and again increased. As the yield components in the first growth, the proportional weight of tillers appeared at vegetative stage was high and had the ratio of more than 60% even at heading stage. About a half of the yield of the aftermath was occupied by the regrowth of the tillers existing at defoliation at T_2-2 and T_4-2. Tillers appeared immediately after defoliation occupied a considerably high portion of the yield produced by new tiller formation. Tiller size and stem weight ratio in its early growth stage were progressively larger in accordance to its appearance date with advancing stage of the main shoot. This fact suggests that the nutritive value of a tiller may differ with the date of appearance. In conclusion, the auther considers that the differences in the date of appearance of the tillers consisting a plant and in their relative weight as components of the yield portion among the stages of growth, will give an explanation of the differences of digestibility.

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The relationships with the tillering habit reported in the preceding paper and the change of digestibility with the advance of growth stage and the digestibility of the aftermath were examined. Dry matter digestibility was determined by in vitro method. Tillers appeared at late vegetative stage brought an effect to draw up the digestibility of the yield in the first growth, as the digestibility of the main shoot and tillers appeared at younger stage decreased rapidly with the advance of growth. As for the aftermath, the digestibility of the yield at T_2-2 was slightly higher than at T_4-2, and the digestibility of the yield composed of new tillers was higher than that produced by the regrowth of the tillers existing at defoliation. Significant correlation coefficients were obtained between days of growth of the tillers and their digestibility at respective sampling times, but as for the aftermath the coefficient at T_2-2 was not significant and the decline of digestibility with the growth were not big as in the first growth. The rate of decline of digestibility with days of growth was progressively rapid for the tillers appeared at the advanced stage in the first growth. The difference of the rate might come from the difference in growth performance of tillers according to the date of appearance reported in the preceding paper. There was not a significant correlation between the mean growth temperature of a tiller and its digestibility (r=-0.342). Comparing the digestibility of tillers of the same days of growth among the sampling times all the digestibility of the tillers declined rapidly from T_3 to T_4. Some other factors than environmental factors, such as "physiological senescence" of whole plant with heading should be considered. For the purpose of obtaining a higher yield with higher feeding value, it is necessary to harvest at about flag leaf expanding stage prior to heading, and it may be profitable to practice suitable fertilizations to ensure the appearance of larger number of tillers at late vegetative stage in the first growth and ensure the larger number and better growth of tillers which appear immediately after defoliation in the aftermath.

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In the present paper, as a part of studies on forage roots and physical properties of grassland soil, I deal with the root-system distribution of forage grasses and mechanical strength of individual adventitious root. It was used in this examination that Italian ryegrass (Lolium multiflorum LAM.), timothy (phleum pratense L.), Kentucky 31 fescue (Festuca arundinacea SCHR.) and orchardgrass (Dactylis glomerata L.). The results are summarized as follows ; (1) Root-system of grown-up forage grasses formed a tendency to concentrated distribution for the range of certain length. And then, the author named their roots main-roots group. (2) According to the growth stages or species, there was little difference in length and diameter of individual adventitious root which formed main-roots group, ranging 15-25cm in length and 400-600μm in diameter, respectively. (3) Each root which formed the main-roots group showed the maximum tensile strength in one individual. (4) Tensile strength of individual root increases with advance of growth. In case of Italian ryegrass, the adventitious roots of a 20-week growth after sowing had three times as strong as a 4-week stage. (5) According to investigation of a few grass species with a 28-week growth, tensile strength ranking was timothy>Kentucky 31 fescue>orchardgrass. (6) From the results that the roots in the main-roots group were stronger than others in tensile strength, it is suggested that the growth of them was the one of terms advantageous to soil conservation.

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In the present paper, as a part of studies on forage roots and physical properties of grassland soil, I deal with the factors which are related to root tensile strength for forage grasses. In this examination, Italian ryegrass (Lolium multiflorum LAM.) was used. The results obtained are as follows ; (1) There was no significant difference between the external diameter of adventitious root and the root tensile strength. (2) It had not come out clear also that the correlation between the diameter of central cylinder which was a part of root texture and the root tensile strength. (3) Crude fiber content of root wa about 30 percent and it's value made little difference at each growth stage. This result was not consistent with the tensile strength which increased with the growth of grasses. (4) Central cylinder of root took a lignin. This lignification was proceeding with the growth of grasses. (5) It was recognized that the degree of lignification was proportional to the tensile strength of root. (6) It had been suggested that lignification of roots was a main factor for the tensile strength.

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The effects of various rates and methods of N application on the growth and nodulation of Desmodium intortum cv. Greenleaf (De) mixed with Setaria anceps cv. Kazungula (Ks) were studied. To study those effects, 9 treatments of 3 N rates×3 methods of N application to the mixture (M) were made. Also, 3 treatments with no N on the mixture and pure stands of individual legume and grass were included as shown below. The treatments were replicated 3 times. [table] The plants were arranged in a 15cm×15cm grid in the pure stands and alternately in the mixture. Plot size was 2×3m each. Urea was applied just before transplanting (basal N) and an additional N was applied after the first clipping in the first year. Sufficient amounts of the other needed nutrients were applied. Items studied were total DM and total N yield, nodule number and nodule weight. Clippings were imposed when the mean height of any treatment reached 50cm. Three soil cores (10cm diameter×10cm length) per plot, each core representing three plant roots of De, were sampled for the nodule counting. Results obtained are as follows: 1) The growth of De was poor in the first year. DM yield was highest in 16 N due to the vigorous Ks component. The effects of N in increasing DM yield were observed up to the sencond clipping (Fig.1). DM yields were highest under 8N in the second year due to the effect of the legume mixture (Table 1). 2) The mixture effect was calculated as described below (Fig.2). [numerical formula] The effects on De were also calculated in the same way. The mixture effects were significant in the second year. Both Ks and De components in the mixture showed increase in DM yields. 3) DM yields increased in 4N and more significantly in 8N when total N was applied before transplanting (Table 7). This might be attributed to the following: a) In the first year, better establishment of Ks were observed as N rates were increased; b) In the second year, the mixture effects were increased in those plots. 4) Increased N yield followed the pattern of the increase in DM yields. DM yield of De increased in 4N and 8N and decreased in 16N as compared to ON (Table 2). N content of Ks component in all the treatments showed almost identical values at the third clipping (Fig.3). N contents of De component at the third clipping were higher in 4N and 8 than in ON and 16N. Active N fixation might be suggested in 4N and 8N. 5) The effects of basal N rates on the nodule formation were examined at the first clipping in the first year (Table 3). The nodule formation and development were stimulated with increased N rates up to 8kg N/10a as compared with Okg N, and decreased with 16kg N. Also, the number of white nodules per plant were increased with 16kg N. The effects of basal-additional N ratio were evaluated in the 4N and 8N plots (Table 4). The number of nodules per plant and the weight per nodule were higher when all the N were applied as basal compared to the split application of N. 6) In view of the DM and N yields and the effects of N on the nodule formation in the first year and the mixture effects in the second year, the N rate of approximately 8kg/10a applied mainly as a basal is recommendable under the field conditions similar to this experimental field.

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The effects of various conditions of temperatures and light intensities and rates of N application on the early growth of Desmodium intortum cv. Greenleaf and its symbiotic N fixation were studied using the ^<15>N. To study those effects, 24 treatments of 3 temperature regimes (20°, 25°, and 30℃ of the day and night temperatures)×2 light intensities [full light (L) and shade (S), 50% of full light]×4 rates of N application (0N, 1N, 2N and 4N) were made. Plants were sampled 40 days after the treatments were imposed. (N≒1kg/10a) Items studied were total DM yield, Leaf Area, nodule number, nodule weight, total N yield and the portions of N originated from N fertilizer and symbiotically fixed N. Results obtained are as follows: 1) DM yield (Table 1) increased with higher temperature and increased rates of N application. However, at 25℃ under S treatment, DM yield was lower at 4N as compared with 2N. DM yield decreased in the S except for 1N and 2N under 25℃. 2) Leaf Area increased with the higher temperature (Fig.2) and with the S under 25℃. It also increased with 1N and 2N and in some cases with 4N. DM yield per Leaf Area was higher in the order of 25>30>20℃, and also it was higher in the S than in the L. In the L, DM yield per Leaf Area increased with the increased rates of N application excluding 4N under 25℃. There was no significant variation in DM yield per Leaf Area under S. 3) Total nodule number and weight increased with N applications up to 2N (Table 2) and decreased with 4N except in a few cases. They also increased at higher temperatures and L except at 25℃. The weight per nodule increased under higher temperatures and with the N application as compared with no nitrogen application except in 4N. The nodule weight. per Leaf Area increased under 20℃, and no significant differences were observed between 25℃ and 30℃. It also decreased with the increased rates of N application. The nodule weight per DM yield was not significantly affected by temperatures, but decreased with the L. 4) N contents of plants under 25℃ were higher with the increased rates of N application and no clear-cut differences were observed between the L and the S. In the L under 25℃ and 30℃, N contents decreased with the increased rates of N application in contrast to that in the S. Total N yield (Fig.2) increased as the rates of N application were increased except for 4N under 25℃. The amount of N in the plant originated from the N fertilizer in creased linearly as the rates of N application were increased. By contrast, the amount of symbiotically fixed N increased with decreased rates of N application and decreased with in creased rates of N application; and it was stimulated more under higher temperature, but not under the S at 20°and 30℃. The amounts of symbiotically fixed N per nodule (Table 4) were significantly decreased under 20℃ as compared with under 25℃ and 30℃. This also increased with the N application in the S but not in the L. 5) Results outlined above were discussed in view of the differences between the symbiotic N fixation and the absorption of the fertilizer N in terms of the range of temperatul requirements for optimum activity, the effects of N on the nitrogenase and Leghaemoglobin syntheses and differences between the symbiotic N fixation and the absorption of the N fertilizer in terms of carbon economy. It was concluded that the symbiotic N fixation was easily affected by the changes in environmental factors as compared with the absorption of the fertilizer N by plant. Also, the low rates of N application increased not only DM production but also the symbiotic N fixation even under low temperature provided light energy in sufficient amounts. Finally it can be stated that the N application at the low rates overcame the low rate of the symbiotic N fixation in the early spring of low temperature. Also, low rates of N application maximized both N yield and the symbiotic

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This study was conducted to compare the effects of three levels of manure and urine applications on the chemical composition and the feeding value of soiling oats (Onward) during five years, from 1972 to 1976. Levels of application per 10a during one cropping period were ; High level plot: manure 15, 000kg plus urine 6, 000kg Low level plot: manure 5, 000kg plus urine 2, 000kg Control plot: no manure and urine, N 16.3kg as ammonium sulphate, P_2O_5 11.8kg as superphosphate and K_2O 17.0kg as muriate of potash. Oat plant was sown at the rate of 7-5kg per 10a in 60cm rows on Nov.8 in 1972 and 1973, and on Nov.27 in 1974 and on Nov.28 in 1975, respectively. Harvesting was made on Apr.13 in 1973 and Apr.30 in 1975 (boot leaf stage) and May 6 to 19 in 1976 (before heading to early heading stage), respectively. (Removal: Oat forage of all treatments brought down by rain rotted in 1974.) Digestibility was estimated by the conventional collection digestion trial with sheep. All materials were chopped into 5 to 7cm, and fed to sheep as green forage, sun-cured hay or silage. The results were summarized as follows: 1. Crude protein content of the high level plot was the highest throughout experimental years, especially higher than other treatments in 1973. Also, crude protein content of the control plot was significantly higher than that of the low level plot in 1973, 1975 and 1976. 2. NFE content of the low level plot was the highest throughout experimental years, especially higher than other treatments in 1973. Also, NFE content of the control plot was significantly higher than that of the high level plot in 1975. 3. Calcium content of all treatments at the boot leaf stage showed to be higher than that of all treatments at the early heading stage. 4. Magnesium content of all treatments showed a tendency to decrease as experimental year advanced. 5. Potassium content of the high level plot showed the highest throughout experimental years. Potassium content of all treatments in the first annual showed the lowest throughout experimental years. 6. NO_3-N content of the high level plot was the highest throughout experimental years, especially higher than other treatments in 1973. Also, NO_3-N content of the contro plot was significantly higher than that of the low level plot in 1975. 7. In comparisons with digestibility of each chemical composition in green forage, suncured hay and silage, digestibility of crude fat in silage was the highest and digestibility of NFE in silage was the lowest. 8. Silage qualities of all treatments were ranked inferior grade.

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