Drying methods of green panic seed were investigated for obtaining better germination, because the methods might have remarkable effects on seed germination afterward, as suggested in some experimental results. It was recognized that drying speed played decisive role as well as drying temperature for controlling germinating behavior of seed. Rapid seed drying injured germination, and the injurious effect occurred in an early stage of drying after harvest, affecting to a portion of seed except bract. Germination of seeds dried at 30℃ or 40℃ were better than those of seed dried at 20℃ or 15℃, when the seeds had been dried slowly at these temperatures just after harvest. Germination percentages of seeds dried at 20℃ or 15℃ decreased with time of storage for longer than one and a harf year at room temperature. Decreasing rates were higher in seeds stored at 30℃ than at room temperature. Those seeds showed high germination percentages and rapid germination, provided their bracts had been removed. Seed stored at 30℃ for 2 months in wet condition could not germinate at all. But seed stored at 20℃ or 15℃ in the same conditions showed very good germination several months after harvest. Excellent germination was produced 7 months after harvest, if the seed had been dried very slowly for a month at 20℃. From these results, two methods of slow drying of seed immediately after harvest were shown for obtaining excellent germination afterward as early as possible ; 1) Drying for several days at 30℃ in a shallow tray. But there was a risk of failure in this method by inadequate drying speed. 2) Drying for a month at about 20℃ in a vessel, and stirring seed at intervals of some days to dry all grains uniformly.

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Effects of temperature regime, mode of rainfall and light intensity during seed ripening on germination of green panic seed were examined. Germination of seed ripened at 29℃ was worse materially than those of seeds ripened at 25℃ or 21℃. Germination percentages of seeds exposed to rainfall during ripening were higher than that of seed met with no rain during ripening untill a year after harvest, but thereafter, the latter increased more speedily with seed age, and attained its maximum about 2 years after harvest. While seeds exposed to rainfall delayed to reach their peak germination. Germinating speed of seed exposed to a misty rain every day was more rapid than that of seed met with no rain. However, germinating speed of seed exposed to an intermittent rainfall every day was slowest. Seed in shade during ripening showed higher germination percentage 9 month after harvest than seed in full light during ripening, while heavy shade (light intensity was 20% of full light) brought slow germinating speed. In common in three experiments in this article, seed which was dried slowly during ripening showed better germination within several months after harvest, as seed previously reported which was dried slowly immediately after harvest did so. Based on these results and field experiences, it was discussed what were the suitable weather conditions during seed ripening for production of seed with better germinability in its early age.

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Changes in dry matter weight and structure of sward were investigated throughout a year on bahiagrass pasture grazed by Holstein heifers under rotational system. Outlines of results obtained are as follows. 1. Standing crop over a year ranged from 1390 to 1890g/m^2. Relative dry matter distribution of organs in standing crop changed in the ranges of 0-1% for ear, 1-15% for leaf, 7-18% for stem, 4-14% for standing dead, 22-36% for stolon and 35-50% for root. Consequently, C/F ratio was high ranging from 5 to 146. 2. As for aboveground parts, most dry matter was concentrated in the stratum of 0-10cm, and stem and standing dead occupied so much amount as more than 66%. This fact was considered as the reason for high canopy extinction coefficient. 3. So far as the regrowth or persistency was not depressed, close grazing to lower aboveground stratum was inferred as one of the pasture managements for higher solar energy utilization in bahiagrass pasture from the reasons as (1) increasing herbage intake by cattle, (2) increasing relative amount of leaf and reducing that of standing dead in aboveground dry matter, and (3) possibly improving canopy extinction coefficient.

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Net primary production and efficiency for solar energy utilization were investigated over a year on bahiagrass pasture rotationally grazed by Holstein heifers. Calorific value and energy mass of the sward, and rate of litter disappearance were also investigated. Outlines of the results are as follows. 1. Calorific value of the sward changed in the ranges of 4.25-4.69Kcal/g (17.8-19.7KJ/g) for ear, leaf and stolon, 3.95-4.23Kcal/g (16.6-17.7KJ/g) for stem and standing dead, and 3.43-3.91Kcal/g (14.4-16.4KJ/g) for root and litter. 2. Energy mass of standing crop ranged from 5278 to 7855Kcal/m^2 (22.1-32.9MJ/m^2) and that of total organic matter including litter ranged from 6539 to 9998Kcal/m^2 (27.4-41.9MJ/m^2). Relative energy distribution of organs in standing crop changed in the ranges of 0-1% for ear, 1-17% for leaf, 7-19% for stem, 4-14% for standing dead, 24-40% for stolon and 32-48% for root. 3. Rate of litter disappearance ranged from 0.00044 to 0.00632g/g/day and a great difference among the seasons was observed. 4. Efficiency for solar energy utilization in net primary production ranged between -0.38 and 1.33% being high in summer and low in winter. 5. In this study, bahiagrass pasture received solar radiation (total short wave) of 1214879Kcal/m^2 (5090.3MJ/m^2) over a year, and out of this, 6916Kcal/m^2 (29.0MJ/m^2) was fixed by the plant as a net primary production with an efficiency of 0.57%. Further, from this amount of net primary production, 41.4% of energy (2863Kcal/m^2, 12.0MJ/m^2) transferred to grazed herbage, 24.0% (1657Kcal/m^2, 6.9MJ/m^2) to mowed herbage and 30.6% (2116Kcal/m^2, 8.9MJ/m^2) to litter production. Then, energy stored in the plant was only 4.0% (280Kcal/m^2, 1.2MJ/m^2) and almost all the energy fixed by the plant as a net primary production transferred to the outside of the plant on an annual basis.

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Laboratory and field experiments were conducted to determine the relative toxicity of stubble-residues from 11 tropical grasses to the following crop of Italian ryegrass (Lolium multiflorum, cv. Minamiwase, Abbr. as IRG). In the laboratory, IRG seeds were germinated in petri dishes containing various aqueous extracts of the residues. Ten days after seeding, percent germination was determined and shoot and root lengths were measured. In the field, the residues on pure plot of each tropical grass were buried in the soil with plowing and IRG seeds were sown into the plot. Plant density at 2 weeks after sowing and dry matter yield cut 2 times at heading stage were determined. The results obtained are summarized as follows: 1. Germination of IRG was generally found to be reduced with increasing in concentration of residue extracts. Extracts of African millet (Eleusine coracana), Guinea grass (Panicum maximum, strain GR-171) and setaria (Setaria anceps, cv. Nandi and Kazungula) were very inhibitory to the germination of IRG at a high concentration (4g dried stubble/100ml water) ; whereas in the lower concentrations (1, 2g/100ml) there were no pronounced differences in germination among extracts of tropical grasses. 2. Root length of IRG seedling was considerably reduced but shoot length was slightly increased with increasing concentration of extracts. Extracts of African millet, Guinea grass (GR-171), Rhodes grass (Chloris gayana, cv. Katambora) and Kabulabula grass (Panicum coloratura var. Kabulabula, strain GR-29) suppressed markedly root growth of IRG, while there were no pronounced differences in shoot length among the extracts of 11 grasses. 3. The results in the field experiment, showing the lower plant density and yield in each plot of preceding African millet, Guinea grass (GR-171) and setaria (Kazungula and Nandi), were in agreement with the germination and root growth at 4g-concentration in the laboratory. Significant correlation was obtained between percent germination at 4g-concentration and dry matter yield of IRG.

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Seasonal dry matter production was measured in the grazed pasture of Agrostis alba L. (redtop) from 1979 to 1981. In 1979 and 1980, the pastures were applied with the conventional rate of nitrogen (the CN plot: 290kg/ha/year), and with the higher rate of nitrogen (the HN plot: 810kg/ha/year). In 1981, both plots were applied with the lower rate of nitrogen (110kg/ha/year). Biomass of grasses and separated parts as leaf, stem, standing dead and underground were measured monthly from March to November in each year. Principal component analysis (PCA) was applied to these data to clarify the factors that affect the seasonal dry matter production in the grazed pasture. The variables used in principal component analysis were the growth rate of each part of plant, the standing crop of each part at the time before the biginning of spring regrowth or at the time just after the grazing cattles were transferred out from the experimental paddock ("Dry matter weight 1" in Table 1), and the sum of the intake by the grazing cattles and the residual forage at each grazing period or the standing crop at late autumn ("Dry matter weight 2" in Table 1). The results obtained are as follows. The first principal component (PC1) is the factor on the total living biomass, and about 31% of the total variation are explained by PC1. The second principal component (PC2) is the factor on the standing dead biomass, and about 22% of the variation are explained by PC2. The third and the fourth principal components (PC3 and 4) are the factors on the leaf biomass and on the underground biomass, respectively. Cumulative contribution of these four principal components is 80% of the total variation. By the score of PC1 and 2, the seasonal change of dry matter production in the grazed redtop pasture is summarized in five types of variation corresponding to five periods during a growing season (Fig.4). They are (1) from spring to early summer, PC1 has high positive values due to the spring flash, (2) in the first half period in the rotation, both PC1 and 2 have positive values, (3) in the latter half period in the rotation, PC1 has negative values and PC2 has positive values, (4) in early spring, both PC1 and 2 have negative values, and (5) in late autumn, PC1 has high negative values.

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The absorption of mineral nutrients by corn in ill-drained clayey soil converted into upland field was examind for four years. Zea mays cv. Takanewase was grown in three conditions of nitrogen level, i.e. none, standard and heavy (1.5 fold) application. Total nitrogen (N), Phosphorus (P), Potassium (K), Calcium (Ca) and Magnesium (Mg) contents at the stage of heading and yellow-ripening were measurd. The percentage of N, P and K contained in the leaves and stems at the yellow-ripening stage was lower than that at the heading stage, but that of Ca and Mg were higher on the contrary. When compared with the contents of the elements in leaves, stems and ears at the yellow-ripening stage, higher percent of N, Ca and Mg were observed in the leaves and that P and K in the ears and stems respectively. The yeary change of contents of the elements was remarkable in the leaves and also the first year harvest contained markedly low amount of the elements except K. The percentage of N and P in the leaves increased with the laps of time but P in the stemes decreased gradually. The yearly change of the elements in ears was not big as that in leaves and stems. The contents of elements, except K at yellow-ripening stage, increased with years after conversion. Especially N was most remarkable in the comparison of the two stage. The ratio of N contents at yellow-ripening stage and heading stage was 60% in 1st year, 82% in 2nd year and 148% in 4th year. In the heavy nitrogen application treatment, the percentage of almost of all the elements in the leaves were high every year but that of P in the stems was low. The content of each element increased with nitrogen application. Thus, the absorption of the elements, especially N and P, in ill-drained clayey soil was inhibited in the early years after conversion. But it was gradually improved with years. It was found also that heavy nitrogen application was effective in promoting nutrient absorption.

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The changes in spatial pattern of pasture plant species and spatial relationships among them were examined for half a year after seeding in five simulated swards. A pure sward of timothy, and four mixed swards (with orchard grass, kentucky bluegrass, white clover, and all these species, respectively) were set up in a greenhouse, and two permanent quadrats (15×15cm^2) were placed in each sward (41.5×26.5×8.0cm). Spatial distribution patterns and spatial relationships among species were analysed by means of Morisita's Iδ-index and Rδ-index, respectively. The spatial pattern of broadcasting seeds of all species was random to weakly aggregated one, but that of each species was random to aggregated one. No relations in distribution among species were found in many cases. On 18 days after seeding, total germinated seeds of all species were distributed more aggregatedly and positive relations were found in several plots. Distribution of surviving plants became more random 4 months later, and little shift was observed after that. Spatial patterns were considerably different among species at the last recording date, dominant species were distributed regularly to weakly aggregatedly but suppressed species were distributed more aggregatedly. These results suggest that spatial pattern of total plants of all species in a sward becomes rapidly more random even if it was aggregated immediately after seeding, and spatial pattern of dominant species becomes more random but that of suppressed species becomes aggregatedn the process of development of dominance-suppression relationship within a sward.

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We are studying new method of ploughless pasture establishment. This method combines the use of a Stump-cutter to cut stumps and a Bush-cutter to crush bushes. We compared 4 methods using different combination of these machines. In this paper, it is made clear what the influences of these establishment methods are in the inhibitation of the original vegetation, on the condition of the sowing bed and on grass growth there. The inhibitory effect on species of plant which appeared before with after construction was compared. Also, the influence of each method on the condition of sowing bed, on grass growth the crushing degree of bushes on surface soil and number of germination or crown coverage of grass were investigated. The results are summarized as follows. (1) Regrwth was not obserbed on stumps cut by the Stump-cutter. (2) The inhibitory effect of the Bush-cutter on the native plants was more effective when the bushes were crushed after removing the cutted stumps. (3) The sowing bed had a thick layer of crushed plants when every stumps was crushed in place, and this had an inhibitory effect on grass growth.

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