When grass seeds are sown after plowing the sloped land, the germination and establishment are often uneven. The experiment was done by using Italian ryegrass in order to find out this cause. Following results were obtained: 1. The water absorption rate at 25℃ was 79% in glume seed, and 74% in glumeless seed, respectively, at the time of 80% in germination percentage. 2. Even if the maximum temperature in daytime was 30℃, seeds without soil cover germinated normally so long as the humidity at soil surface was 90%, while germination at 60-70%, in humidity was very poor. 3. When the size of clods was smaller than 5mm in diameter, seeds could only germinate on the soil surface with high moisture. 4. However, it was observed that seed was able to germinate even though the size of clods was 10-20mm in diameter and soil surface was low in moisture, because it fell into a gap between clods to get enough moisture.

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This experiment was carried out to clear the effect of various kinds of litters covered the soil surface on the germination and the seedling growth of Italian ryegrass sown by sod-seeding method. The litters used in this experiment were leaves of sasa, pine-tree, and oak. Pot without these litters was prepared as the control. The results obtained were as follows: 1. Germination percentage was 12% in oak litter, 12% in sasa litter, 3% in pine-tree litter, and 73% in the control at 10 days after seeding. 2. After 30 days, the percentage of established Italian ryegrass sown on each of oak, sasa, pine-tree litter, and the control was 85, 53, 31, and 85%, respectively. 3. Seeds which did not germinate in each plot were collected and tested their germination percentage again. Germination percentage was 87% in oak, 91% in sasa, 97% in pine-tree, and 33% in the control. 4. Germination rate and percentage tested by using percolates from each litter was lowest in pine-tree. 5. The percolate from pine-tree litter suppressed the early growth of seedling more than any other percolates.

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On sloped lands, it is necessary for seeding grasses to save labor and to promote the seed germination and establishment. This experiment was carried out to find how to make seed pellets and their effect on the germination and the early growth. In this experiment, Italian ryegrass seeds were used, because none of seed pelleting has been reported on grass seeds, but on legume seeds. Moreover, in Shikoku Island, grasses are more used than legumes, since climate, soil condition, and cattles (dairy cattle) favor grass growing. Another reason for adopting Italian ryegrass seeds is that the seeds are comparatively large-sized and, if the pelleting is possible on this grass, it may applicable to other grass seeds. The experiment was done from August, 1970 to November, 1971. Firstly, materials to compose pellet were examined. It was revealed that synthetic resion was suitable as the cementing material, and as the medium, slaked lime mixed with peat was good for promoting percentage and speed of germination. Addition of fertilizer into pelleting was also investigated. It was found that the most suitable rate of fertilizers was to mix 5-10g of Italian ryegrass seeds with 50-100g of slaked lime, 20-40g of peat, 10-20g of urea, 40-50g of calcium phosphate, 10-20g of potassium chloride, and 60-80ml of 20% liquid synthetic resion. The pellet was made to less than 10mm in diameter. By this pellet, there was observed no harmful effect on germination, and a beneficial effect of mixing fertilizers on the growth at 60 days after seeding.

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This experiment was conducted to make clear the relationship in growth between main shoot and its tillers in grasses. Grasses used were tall fescue (Festuca arundinacea SCHR.), orchardgrass (Dactylis glomerata L.), timothy (Phleum pratense L.), tall oatgrass (Arrhenatherum elatius (L.) MERT. and KOCH), Italian ryegrass (Lolium multiflorum LAM.) and perennial ryegrass (Lolium perenne L.). One primary tiller (the rest tillers being removed) of each plant was shaded with a black cheese cloth. The results are summarized as follows: (1) Increases in the top dry weight and in the number of tillers per plant were checked by shading the tiller. (2) In any grasses, there was a marked repression in the increments of dry weight, leaf area and number of secondary tillers in the shaded tiller regardless of its leaf age (2 to 10 leaves), but the rate of reduction varied according to the grass species. The reduction of tall fescue was greatest, followed by that of orchardgrass, timothy and tall oatgrass, and that of Italian ryegrass and perennial ryegrass was smallest. (3) In tall fescue, tiller shading decreased dry weight, leaf area and number of tillers of the main shoot, while in Italian ryegrass or perennial ryegrass, it showed little or on decrease in the items above mentioned. (4) The ratio of the dry weight of shaded tiller to total top dry wight decreased in all grasses as compared with that in the untreated plant, the decreasing rate being different according to species. In tall fescue, the ratio was lowest, followed by that of orchardgrass, timothy and tall oatgrass, and then by Italian ryegrass and perennial ryegrass. From the above results, it was shown that in some species the growth of tillers and main shoot was affected seriously by shading the tiller, while in others it was affected relatively slightly.

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Knowledge of the relationship between soil moisture level and drymatter production of forage plant is essential for better management of sward. However, field studies pertaining to the subject are very few especially in Japan. The aim to obtain the quantitative relationship at field level between the soil moisture content and the amount of dry matter production of orchardgrass (Dactylis glomerata L.) which is one of the most fundamental species in Japanese sward, the dry matter production and crop growth rate under various conditions of soil moisture were calculated from eq. (8) and eq. (9) which were examined in the previous paper 7. The constant values of eq. (8) and eq. (9) under various soil moisture conditions were determined based on the results of field experiment in the previous paper 7. and of pot culture experiment in the present study. Pot culture experiment in the present study was carried out under various soil moisture conditions (100%, 70%, 45%, 35%, 25%, and 20% of maximum water-holding capacity) for 17 days from August 21 to September 7 in 1972 to make clear the response of photosynthetic and respiratory activities and leaf area production to the soil moisture. The results obtained are as follows ; 1) Photosynthtic and respiratory activities of orchardgrass were affected by soil moisture conditions. The maximum values of both factors were obtained under soil moisture range from 45% to 70%, and they showed the decreasing trend beyond that range. However, the rate of decline of respiration rate was smaller than that of photosynthetic activity. 2) Leaf area production was more intensely affected by soil moisture conditions than photosythetic and respiratory activities. The highest value of leaf area production was found at the soil moisture ranging from 45% to 70%, and it declined in the order of 35%, 100%, 25% and 20% plots. Leaf size, number of leaf and stem, which are the component of the leaf area also showed the similar response as leaf area production to the soil moisture. 3) Total dry weight and CGR after cutting of orchardgrass sward which were calculated by eq. (8) and eq. (9) were heavily influenced by soil moisture levels. Both values showed the maximum at the soil moisture ranging from 45% to 70% and declined at the outside the range (Fig. 3 and 4). The peak of CGR curve in the regrowing process was shown at the earlier stage after cutting according as the soil moisture level approached to the field capacity (Fig. 4). 4) The quantitative relationship between soil moisture and dry matter production of orchardgrass sward was obtained by calculating the net dry matter production after cutting. And it was concluded from the results summerized in Table 4 that the range of optimum soil moisture for dry matter production of orchardgrass sward was from 45% to 70% (pF 2.7-1.5) of maximum water holding capacity and that the range of soil moisture at which dry matter production was able to gain not less than 40% of that of optimum range was from 35% (pF 4.0) to 90% (pF 0.5).

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The dry matter production of orchardgrass (Dactylis glomerata L.) sward under various conditions of air temperature and radiation were estimated and analysed in this paper. Based on CO_2 balance of the amount of photosynthesis and respiration in community, the dry matter production and crop growth rate under various conditions of air temperature and radiation were calculated from eq. (8) and (9) which were examined in the previous paper 7. The constant values of eq. (8) and (9) were estimated from the experimental results of pot cultivations which were carried out under various conditions of air temperature and radiation. The results are as follows; 1. The rates of leaf area production, photosynthesis in single leaf and respiration were influenced heavily by the variation of air temperature. The rate of leaf area production showed the greatest value at 20℃. The rate of photosynthesis in single leaf decreased at low air temperature below 15℃. The respiration rate of plant increased with increasing of air temperature (Q_<10>=1.65). 2. The influence of air temperature on the dry matter production varied complexly in connection with the regrowth stage after cutting. In this experiment, the dry matter production in community showed the greatest value at 16℃ and this temperature scarcely varied under various conditions of radiation. 3. Among the many factors which were related with dry matterr production, the amount of photosynthesis in community was influenced heavily by the variation of radiation. The dry matter production in community increased with increasing of radiation. But the productive efficiency per a unit radiation showed high value under the low radiation and decreased with increasing of radiation. 4. The periods from the day of cutting till the day when the maximum crop growth rate (CGR max) was showed were calculated from eq. (12). These periods affected by air temperature and radiation. The shortest value of these periods showed at 18℃-20℃ and under the highest radiation.

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Based on the experimental results obtained in previous paper XI, effects of air temperature and radiation on the seasonal dry matter production of orchardgrass sward were analysed in this paper. The results are as follows ; 1. The seasonal changes of air temperature and radiation in each region of Japan were affected by latitude and elevation. Generally, the seasonal changes of air temperature showed the mono peak curves which have a peak in August, but those of radiation varied with changes of latitude and elevation. The regions of higher latitude (Hokkaido districts) and higher elevation (central high land) had a peak of radiation in May or June, but those of lower latitude (south of Tohoku districts) had two peaks in April and August. 2. Calculated values of yearly dry matter production of orchardgrass sward in lower latitude regions were higher than those in higher latitude and higher elevation regions. On the other hand, yealy mean values of crop growth rate (<CGR>^^^) and productive efficiency of radiation (<PER>^^^) in lower latitude regions were lower than those in higher latitude and higher elevation regions. The high values of crop growth rate (<CGR>^^^) and productive efficiency of radiation (<PER>^^^) were obtained in the south-western section of Hokkaido districts, Tohoku districts and central high land. As the reason mentioned above, it may be considered that the most suitable air temperature (16℃) for production of orchardgrass sward was gained in the same season (May or June) of the highest radiation and air temperature in summer season was comparatively low in these regions. The yearly dry matter production, <CGR>^^^ and <PER>^^^ decreased in north-eastern section of Hokkaido districts, because the season (August) of the most suitable air temperature for production of orchardgrass sward did not agreed with the season (May) of the highest radiation and the air temperature during the growth season was comparatively low condition. The yearly dry matter production of south-western section (low latitude) in Japan increased owing to high radiation and long period of growth season, but <CGR>^^^ and <PER>^^^ decreased owing to high air temperatutre in summer season. 3. Changes of CGR of orchardgrass sward during the growth season showed the mono peak curves in the north-eastern section of Hokkaido (peak, August), in the southwestern section of Hokkaido (June) and in central high land (June). The changes of CGR in low latitude regions (south of Tohoku districts) showed two peaks curves which have peaks in spring and autumn season.

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In order to search the physiological method to control bitler-dock weed, Rumex obtusifolius in the pasture, the changes of reserves in the roots and crowns after cutting were investigated. The results obtained were as follows ; 1. Contents of total nonstructural carbohydrates (TNC) in the roots of bitler-dock in the mixture sward decreased sharply during two weeks after cutting. Contents of TNC in the roots were 1.7 to 2.3 times higher than those in the crowns at each sampling time, and this high levels of TNC in the roots indicated that the roots were major organ to reserve TNC and the crowns only played the morphogenetic role in the regrowth through maintaining the growing points for newly developing shoots. 2. In the pot experiments, contents of TNC in both tops and roots steadily decreased during 1 to 2 weeks after cutting, when the tops showed vigorous regrowth. However, TNC contents in the roots exceeded the original levels at 3 weeks after cutting, and increased more thereafter. 3. In the experiments of cutting frequency, no cutting, 2-week interval and 1-week interval cutting during 4 weeks, the regrowth after cutting decreased gradually as the cutting frequency increased. Some plants found to die at the time of 2 weeks after final cutting date in 1-week interval cut treatment. Contents of TNC in the roots at the final cut were 37, 8, and 3% for no cutting, 2-week interval, and 1-week interval cutting, respectively. It was revealed that the regrowth during 1 to 2 weeks after cutting depended mainly on the reserves in the roots and no restoration of TNC occurred during this time and that applying more cutting during this time induced severe decrease of TNC contents and some death of plant. From these, the treatment to decrease TNC content in the roots suggests to be effective to control bitler-dock weed in the pasture.

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In order to analyse the effects of soluble calcium salt on pasture establishment, the authors examined the differences of some characteristics of the soil, root system and community structure among fertilizer-not-applied control, fertilizer-applied control, fer-fertilizer-applied calcium carbonate and fertilizer-applied calcium acetate plots, in 1970 and 1971. The results are summarized as follows: (1). The moisture content of the soil was most abundant in 20-30cm horizon and decreased in 10-20cm and 0-10cm horizons in turn. The differences of moisture content could not be revealed among the treatments (table 1). The abundance of moisture in the lower horizons appeared one of the reasons why the use of soluble calcium salt facilitated the pasture establishment. Available phosphate content was increased in the uppermost horizon by fertilizer application, but hardly recognized in the lower horizons (table 1). (2). The investigation of root system revealed the fact that the density of the root of Ladino clover was increased in 5-20cm horizon by the application of calcium carbonate or calcium acetate. The length of the longest root of Ladino clover was increased by the application of calcium acetate (table 2). (3). According to the results of floristic study, the summed dominance ratio (SDR) of orchard grass in all plost and that of Ladino clover in the plots of calcium acetate or calcium carbonate ranked first or second. The numbers of weed species were decreased with promoted growth of harbage plants by the application of fertilizer or lime and fertilizer (table 3). The A/F ratio of Ladino clover applied with calcium acetate was higher than that of Ladino clover in the other plots or orchard grass in each plot in 1970, which indicated its randomness of distribution and then it decreased in 1970 (table 3). Ladino clover and orchard grass were beside the geometrically progressive relationship of the density-rank of species in the plots applied with calcium acetate or calcium carbonate (figure 2). There were negative correlation on densities and coverages between Ladino clover and orchard grass, when calcium acetate was applied (figure 3). It was concluded from these results that, though calcium acetate promoted pasture establishment, the relationships between harbage plants or harbage plants and weeds were not yet attained to stabilization and in the midway of succession.

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