The effects of plant density in combination with two cutting frequencies on the yield of orchardgrass swards were investigated in order to elucidate the appropriate plant density for maintaining high grassland productivity. The variety used for this experiment was "Kitamidori". Orchardgrass was shown in paper-pots in early summer and then transplanted to the experimental field in Sapporo in Semtember 1969. The split plots design was used. Two cutting treatments (3 times a year, 6 times a year) were allocated in main plots and 5 plant densities (11, 44, 100, 178, 400 plants/m^2) were in sub plots. Prior to transplanting, 25g CaO, 20g N, 15g P_2O_5 and 10g K_2O per m^2 were given as basic fertilizer, and furthermore, each of the 20g N, 7.5g P_2O_5, 15g K_2O were topdressed in the second and third years following. The most appropriate density of all was defined as the one beyond which no more in dry matter yield of grass could be expected. The results are summarized as follows ; 1) Under different LAI levels, both NAR and CGR in the low point density were higher than those in the high density as previously reported. Among the main reasons were (1) the lower plant height, (2) the unfavorable production structure, and (3) the lower nitrogen level of blades in the high density as compared with the low density. 2) The regrowth of the plants of the high density was also inferior to those of the low density during summer. In the following are the reasons for it. (1) The dry matter weight of stubble per unit area gained with increasing plant density, while the percentage of TAC and N in the stubble declined. (2) The regrowth root weight per unit weight of stubble and the vitality of root increased with decreasing density. 3) In the three-cut treatment the percentage of plants killed in the second year soared with increasing density. The rate of the dead in the highest density amounted to as much as 65 percent, thus causing a reduction in the dry matter yield. 4) The highest dry matter yield per unit area was obtained in the density of 100 plants per m^2 in the first year and in that of 44 plants per m^2 in the second year, irrespective of cutting treatment. Judging from the results obtained in the present experiment, it was assumed that the appropriate density for keeping high productivity of orchardgrass sward may be around 100 plants per m^2 in such a region as Sapporo.

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Orchardgrass clones collected from Nemuro and Sapporo areas were evaluated on the field of Konsen Agr. Exp. Sta. at Nakashibetsu-cho in the eastern area in Hokkaido. Date of heading, plant height, number of panicules and green yields (the 1st crop, regrowth and their total) were measured under clonal line plots over 4 years from the 2nd year to the 5th year after the experimental plots had been established. The results may be summarized as follows. 1) Green yield of the 1st crop of Nemuro group was higher than Sapporo group, but regrowth yield of the former was lower than the latter. 2) The genetic variations, h^2 and G.C.V., within Nemuro group were smaller than that within Sapporo group on most of the characters. 3) Several parameters estimating the repeatability of characters through years or seasons, h_r^2, r_g and σ_<gy>/σ_g, as defined in the notes of table 2, showed that Nemuro group had higher stability for yearly different conditions than Sapporo group. 4) Higher yielding clones within Nemuro group showed relatively lower regression coefficient and standard deviation from regression than those within Sapporo group. But some clones of Sapporo group had higher yielding potentials with higher stability. It was supposed that the climatic conditions of the eastern area are effective for primary screening of clones in the orchardgrass breeding programs.

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An experiment was carried out in order to find out the efficient techniques for improving the Miscanthus type natural grassland, one of the most common type in Japan. The aerial parts of the vegetation, mostly herbaceous plants, were chopped by rotary cutter, and afterward, two treatments were made as the methods of seedbed preparation i.e. conventional (ploughing and harrowing) and surface tillage. Seeds of orchardgrass and ladino clover were broadcasted in these treated fields. Yields of dry matter and crude protein, vegetation of particular native species and soil characteristics were compared in these two pastures from 1968 to 1972. The following results were obtained. 1. The pasture established by surface tillage was inferior to that of established by ploughing-harrowing in seedling establishment, owing to competition with native species which escaped from elimination. The native species persisted for relatively long duration after disturbunce were Miscanthus sinensis, Pteridium aquilinum, Cirsium Japonicum, Lactuca dentata, Hydrocotyle ramiflora etc. However, their species number decreased gradually year by year, and their weight and coverage decreased considerably after the first harvest of the first year, in particular in third and the fourth year. 2. Dry matter yield of the pasture established by surface tillage was inferior to that of established by ploughing-harrowing, buttheir difference was only a small amount. No significant difference was recognized between the two pastures in total dry matter yield including weeds and in crude protein yield excluding weeds. 3. Soil layer of 0〜5cm of the pasture established by surface tillage had higher nitrogen content and more developed crumbled structure than that of the pasture established by ploughing-harrowing. 4. It is suggested that the pasture establishment by surface tillage is advantageous in steep lands, because it keeps the fertile humus soil in surface layer and maintains native plants which protect soil erosion and young seedlings of sown species in adverse condition. Techniques of the surface tillage method comparing with the convensional method for improving the natural grasslands in hilly country were discussed from these results as well as from the other informations.

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For utilizing barnyardgrass (Echinochloa Crus-galli BEAUV. var. caudata KITAGAWA) as a forage crop, the experiments were conducted to obtain the fundamental data on the daily changes of shedding habit and germination capacity of the seeds after heading. These informations were thought to be useful for the seed production, the practical use of the naturally dropped seeds of barnyardgrass in the successive cultivation with Italian ryegrass, and the countermeasure for keeping off the escape of barnyardgrass. The shedding habit was shown as the percentage of the seeds shed from the pedicel when an ear was slightly grasped in a hand and was pulled by another hand. The germination capacity was shown as the percentage of the germinated seeds in petri dish after the seeds awakened from their dormancy. 1. The first shedding seeds from the pedicel appeared on eight or nine days after heading. The percentage of shed seeds increased straightly with time from the first appearance of shedding, and reached about 50 percent by 20 days after heading. 2. The shed seeds showed 95 to 100 percent of germination in the germination test by using petri dish. 3. Forty to sixty percent of the non-shed seeds obtained the germination capacity on 19 to 20 days after heading. 4. The germination capacity of whole seeds including shed and non-shed sheeds increased by about 4.8 percent per day and reached about 80 percent on 20 days after heading, showing a high positive correlation with the number of days after heading.

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In order to obtain the data on the periodical changes of the viability of barnyardgrass (Echinochloa Crus-galli BEAUV. var. caudata KITAGAWA) seed, a germination test was carried out by using the air-dried seeds stored under the three different conditions of temperature and also by using the seeds kept in soil. The results obtained were as follows: 1. The seeds matured in autumn were dormant. The dormant seeds awakened after a certain period, and after that, the secondary dormancy was not observed on these seeds in any case. 2. In the case of air-dried seeds, the period for dormancy awakening was varied according to the storage conditions: three to seven months in the indoor storage (10〜20℃, in winter), six to eleven months in the outside condition (-2.1〜30.7℃ of every ten days average, in a year), and one to two years in the low temperature storage (5℃). It is considered that higher temperature accelerates breaking dormancy. 3. About 50 percent of the seeds kept in soil started to awaken within one month after dropping, and began to have the germination capacity under the alternating temperature condition (30℃/20℃). These seeds perfectly awakened from their dormancy by next February to April. 4. The air-dried seeds stored either indoor or outside lost their viability rapidly under high temperature in the second or third summer from harvesting. On the other hand, the life-duration of seeds was longer than four years when they were kept under low temperature condition. 5. Eighty-five to ninety percent of the seeds located in 0〜0.5cm of upper soil emerged naturally from late April to September of next year, and by the second year, about 50 percent of the seeds located 0.5〜3cm in soil depth also emerged in the same season within two years. The rest of the seeds located in above-mentioned soil layers and the seeds located in the soil deeper than 3cm almost died within three years. The life-duration of the seeds under humid and submerged soil condition was longer than that under upland condition. Also, seeds in deeper soil layer could keep their viability longer than those in upper soil layer.

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It is evident that Rumex obtusifolius invades tame pasture by means of the diffusion and the spread of the seeds produced by wild Rumex obtusifolius around the pasture. Therefore, it is essential for the effective control of Rumex obtusifolius to disturb the reproductive phase or to interrupt the process of the seed maturity. With a view to surveying the possibility of the above control method, it was carried out to evaluate temperature and day-length influences on the heading and the flowering of Rumex obtusifolius, and to determine the time of flowering of various perennial plants growing in the same field in Nasu, Tochigi-pref. The results obtained were as follows ; 1) The heading of the plants growing under 12hr. or shorter day-length was never able to be induced at any day/night temperature regime. These plants remained in the state at the beginning of the reproductive phase until late in June. Under natural and 16hr day-length, however, the heading and the flowering were induced at all the temperature regimes of 30℃/20℃, 20℃/10℃ in the controlled green house, and natural temperature from May to June in field. 2) Under the same long day-length over 12hr., both the heading and the flowering were hastened as temperature regime increased from 20℃/10℃ to 30℃/20℃. On the other hand, at the same temperature regime the heading was hastened as day-length increased over 12hr., but the flowering would scarcely be influenced by day-length. 3) The high temperature regime of 30℃/20℃ resulted in a marked decrease in the period from heading to flowering. From the assessment of the above results, it is apparent that temperature may strongly affect the period from heading to flowering, and consequently hasten the time of flowering. 4) The time of flowering of various perennial plants growing in the same field in Nasu, Tochigi-pref. was determined. The flowering appeared from early June to early July, mostly mid-June. The variance of the time of flowering of the plants more than a year old shows that the flowering may depend not only on day-length and temperature, but also on the endogenous factors.

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Seasonal changes of tiller bud development on each successive node of orchardgrass shoot, sampled from a sward cutted 4 times a year, were investigated. 1) At the 1st cutting of 10th May 1972 (heading stage), almost all tillerbuds attached to the nodes above N8 of vegetative shoot were depressed, and 1 to 2mm in length (Fig.1). 2) Two weeks after the 1st cutting, the buds of upper nodes (N3 or N4) began rapid elongation, but the most of lower buds (N6 or below), the growth of which was inhibited during influorescence production, remained dormant. Lateral buds left in the stubble of heading shoot elongated partly after the removal of culm, however they were less vigorous and many of them died during elongation in the subtending leaf sheaths. 3) From July to early September, the development of most tiller buds of upper nodes was suppressed with increasing temperature. Most of the lowertillers, elongating or resting, lost vigour and decayed during summer depression. 4) The buds of upper nodes recovered active development as mean air temperature fell below 20℃ in the middle of September. They continued to grow normally, descending the nodal positions with the successive expansion of leaves on the mother shoot. Accordingly, tiller size was progressively larger in lower node between N3 and N8 at November 2.3 5) The tiller bud of orchardgrass may be highly sensitive to environmental conditions at the stage when the bud has just completed its organization for the further elongation. Thus some of the tiller buds grow out as fully emerged ones, and the other stay in a resting state, resulting seasonal fluctuation of the tiller population.

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Corn plant material was ensiled in plastic bags at four stages of maturity ranging from early milk to glaze stage (at approximately 10 days intervals) in 1972, and fed to sheep in digestion trials. All silages were well preserved and range of pH was from 3.7 to 3.8. Dry matter ranged from 15% to 26%. Percent crude protein, crude fiber, ADF and ADL were decreased with increasing maturity. Digestibility of dry matter, carbohydrate and energy were significantly affected by maturity increasing to maximum at milk stage and decreasing slightly thereafter. Increasing maturity significantly decreased digestibility of crude protein, crude fiber and ADF throughout the harvest period. DCP, TDN and DE content in early milk, milk, dough-dent and glaze stage were DCP ; 7.9, 7.0, 6.1 and 5.3%, TDN ; 70.0, 72.8, 73.1 and 69.8%, and DE ; 3.40, 3.60, 3.50 and 3.16 Kcal/g DM, respectively. Nitrogen balance test showed the effects of corn maturity. The nitrogen retension was found to be higher while feeding dough-dent and glaze stage silage.

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