Four tropical legumes were sown each month from Jan. to Dec., 1980. Number of germinated plants and per-cent ground coverage of the legumes 30d. and 60d. after sowing were measured for estimating the most suitable time for an establishment of tropical legume pasture in South-Western Islands of Japan. In view of the plant data and the climate prevailing in this area, the most suitable sowing time of each legume species was estimated as follows ; Macroptilium atropurpureum cv. Siratro-Mar. to Jun. and Oct., Glycine wightii cv. Cooper-Apr. to Jun. and Oct., Stylosanthes guianensis cv. Endeavour-Jun., and Stizolobium hassjo-Feb. to Jun.

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Annual total and seasonal change in digestible dry matter (DDM) production together with in vitro digestible dry matter percentage (IVDMD%) were compared for the second year's plant materials obtained from the previously reported experiment in order to select suitable grass species growing with Siratro. The plant materials and the treatments employed were described in the previous paper (III). Annual yields of DDM were in decreasing order of setaria grass≒pangola grass>Guinea grass>Rhodes grass>Bermuda grass growing in mixture with Siratro. Daily DDM production were higher from Jun. to Sept. in pangola grass or in Guinea grass and from Mar. to Sept. in setaria grass mixed with Siratro. IVDMD% of the grasses were in decreasing order of setaria grass>pangola grass>Guinea grass>Rhodes grass>Bermuda grass, showing higher values under shorter clipping intervals. IVDMD% of each species was decreased during drought periods and hot seasons. Compareing with the mono-cultured grasses, higher IVDMD% and DDM production rates were maintained in the mixtures even during hot seasons and potential of Siratro mixed with setaria grass or with pangola grass were much stressed.

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A field experiment was conducted to study the effects of nitrogen level and regrowth period on the growth and nutritive value of green panic (Panicum maximum var trichoglume cv. Petrie). A 6×3 factorial design in triplicate of six nitrogen levels and three periods of regrowth was employed. The nitrogen levels were 0, 0.50, 1.00, 2.00, 3.00 and 4.00kgN per are ; and the regrowth periods were 3, 5 and 7 weeks respectively. Plot size was 1.75m×2.00m with an effective size of 1.50m×1.75m. Dry matter yield increased with increasing regrowth period. With increasing fertilizer level, dry matter yield increased at 7 weeks of regrowth but showed a decreasing trend with shorter regrowth periods. Nitrogen content increased with increasing fertilizer level but decreased with increasing regrowth period. Nitrogen recovery rates were lower at the higher fertilizer levels but increased with increasing regrowth period. All the cell wall constituents decreased with increasing fertilizer level at 3 weeks but increased with increasing regrowth period. Acid detergent lignin (ADL) content of the fertilized group was higher than that of the control by the seventh week though the differences were not significant. In vitro dry matter digestibility (IVDMD) decreased with increasing regrowth period (p<0.01). IVDMD significantly increased with increasing nitrogen level at 3 weeks but not at other periods.

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A field experiment was conducted to study the effects of nitrogen levels and regrowing period on the dry matter yields, changes in the proportions of forage component fractions, chemical composition and in vitro dry matter digestibility (IVDMD) of these fractions as they affect the nutritive value of the whole forage. The species used in the experiment was green panic (Panicum maximum var. trichoglume cv. Petrie). A 5×4 factorial design in triplicate of five nitrogen levels and four regrowth periods was employed. The nitrogen levels were 0, 14.30, 28.60, 42.90 and 57.20gmN per are per day ; and regrowing periods were 2, 4, 6 and 8 weeks respectively. Dry matter yield increased with increasing regrowing period (p<0.01) as well as increasing nitrogen level (p<0.01). Proportions of green leaves decreased while those of dead leaves and stems (including leaf sheaths and inflorescence) increased with increasing regrowing period. No significant differences were found among nitrogen levels. Nitrogen content increased in all plant fractions with increasing nitrogen levels (p<0.01) but decreased with increasing regrowing period (p<0.01). Green leaves had the highest nitrogen content ; stems had the lowest nitrogen content with dead leaves being intermediate. In all the plant fractions all the cell wall constituents decreased with increasing nitrogen levels but increased with increasing regrowing period. Green leaves had lower cell wall constituents than stems, and dead leaves had either lower or almost the same cell wall contituents as the stems. In vitro dry matter digestibility (IVDMD) of all the component fractions decreased with increasing regrowing period (p<0.01) ; these decreases were 0.71%, 0.29% and 0.81% unit per day for whole forage, green leaves and stems respectively. IVDMD was not affected by nitrogen levels partly because no difference in the proportion of plant fractions among nitrogen levels was observed. It was suggested therefore, that the effect of nitrogen level on digestibility might be limited to situation where an increase in nitrogen content is also accompanied by a large decrease in the cell wall constituents. A very high and negative correlation was found between the cell wall constituents of whole forage or any of its component fractions and their respective IVDMD. Also the correlation between proportion of stems and dead leaves and whole forage IVDMD was negative but that with green leaves was positive.

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We surveyed the floras of ten islands in SAKISHIMA Islands, which located at 24-25°N latitude with the annual mean air temperature and the total rainfalls being 23℃ and 2300-2400mm, respectively (Fig.1 and 2). The semi-natural grassland has been developed on limestone that are poor in water holding capacity and also in fertility. In this area there occurred 23 genera of leguminous plants consisting of 31 species, of which 21 species were found in the semi-natural grasslands (Table 1). The leguminous plants that may contribute to maintain the grassland productivity are ; Leucaena leucocephala, Christia obcordata, Desmodium heterocarpon, D.triforum and D.heterophyllum. The vegetations of the semi-natural grassland can be classified into six types ; Leucaena type, Imperata type, Miscanthus type, Zoysia type, Chrysopogon type and Paspalum type. The floristic composition of Chrysopogon type grassland are intermediate between Zoysia type grassland and. Imperata type grassland. On the other hand, Paspalum type grassland are recognized to carry many agricultural weed communities factors. However, most of the important leguminous plants occurred in the Imperata type grassland and other type grasslands are very simple in the species composition.

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Pasture is not made up of an even distribution but of a mosaic or patched pattern of plant biomass. Such a spatial pattern of plant biomass on pasture might be caused by the interaction of animals and vegetation. The following subjects are dealt with in this paper: (1) Recovery of the spatial pattern with the course of plant growth after grazing on an experimental pasture; (2) Relationships between plant biomass weight per unit area and topological variations of plant biomass weight in any pasture; (3) A theoretical discussion for the model describing the spatial pattern of plant biomass, i.e., gamma distribution.

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For this series of reports, a study was carried out aimed at establishing a technology for stable, long term production of high quality high yielding livestock feed. In order to control forage production successfully, it might be important to know the dynamics of matter, minerals and energy within this type of system. Under intensive forage cultivation practices, high manure applications are inevitable in the present Japan. In this report, energy dynamics were compared for a 5-year period in a double cropping field and a perennial cutting meadow including variations in chemical fertilizer, slurry and solid barnyard manure applications (Table 1). Under the double cropping system, barley was cultivated as a winter crop followed by corn grown during summer. These two crops were harvested and processed into whole-crop-silages. On the cutting meadow, ' orchardgrass was harvested 4 or 5 times a year. It was then artficially dried to make hay. The energy flow and the conversion efficiencies were examined beginning with solar energy on through the grass production and silage processing (Fig.1). The results obtained are summarized as follows ; 1. Average calorific values (cal/g) for harvested portions were 4, 408-4, 565cal for barley and 4, 419-4, 432 cal for corn (Fig.2). Calorific values were generally high in reproductive organs such as ears in barley or cobs and husks in corn, but low in the culms of both these crops as well as in the orchardgrass plant parts. The average calorific values for the harvested portions in 4 cuttings of orchardgrass were 4, 299-4, 355cal/g (Fig.3). 2. In the double cropping system, plots receiving barnyard manure applications, especially the plot receiving slurry manure (A4) maintained high energy yields for the 5-year experiment period. The whole plants of two crops in A4 contained 11, 749kcal of photosynthate and harvested portions contained 10, 591kcal of energy for each square meter of land area during the 1978 year (Fig.4). From the orchardgrass meadow, 6, 568kcal/m^2 of primary energy production and 5, 300kcal of energy yield was observed in the plot G1 receiving chemical fertilizer applications in 1979 (Fig.4). 3. Double cropping of barley and corn showed a higher total primary energy production than orchardgrass cut 4 or 5 times a year. The maximum solar energy conversion efficiencies over the 5-year period averaged 1.06% for the double cropping field (A4) and 0.56% for the orchardgrass cutting meadow (G1) at the primary energy production level (Figs.4, 5, 7 and Table 2). 4. Secular changes of relative energy yield declined linearly in corn at all fertilizer application levels. Slurry barnyard manure application increased energy yields in barley during the 5-year experiment. A similar effect was observed in orchardgrass. But chemical fertilizer application produced a constant reduction in the yield of all the crops (Fig.6).

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This study was conducted to evaluate the effects of botanical composition on the yield of swards in comparison with those of fertilization and soil chemical condition, from the data collected out of 758 cutting swards in Nemuro district, Hokkaido. The results obtained were as follows ; 1) The yield always tended to be higher in the swards where timothy was dominant and legumes were properly maintained, regardless of the amount of fertilizers applied and soil chemical condition. 2) The greater the sum of area percent of crown covers of Kentucky bluegrass, red top and broad-leaved weeds and, that of bare ground, the less was the response of grasses to fertilization. 3) It was hardly recognized that the higher yield of the swards was brought by increasing the amount of fertilizers in the swards where the sum of area percent of the crown covers and bare ground described above was more than 30 percent. 4) From the results, it was concluded that the yield of swards was more influenced by the botanical composition than fertilization and soil chemical condition.

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The main objects of the fall seeding of grass-alfalfa mixtures are (1) to establish the seedlings before winter, (2) to carry them steadily through winter and (3) to produce more forage in the next and subsequent years. The important problems are limited seeding times in fall and cultivation factors to insure wintering of the seedlings. Two experiments were carried out in gray lowland soils in the central district of Hokkaido in 1977-1978 and 1979-1980 respectively. In test 1, both seed mixtures of Senpoku (timothy) -du Puits (alfalfa) and Kitamidori (orchardgrass) -du Puits were seeded on September 24 and October 8 respectively. Two levels of seed, phosphate and potassium were combined according to a L_<32> orthogonal array table. In test 2, both Senpoku-Vernal (alfalfa) and Kitamidori-Thor (alfalfa) mixtures were seeded combining 2 levels of Mammoth-Italian B (Italian ryegrass) as a nurse and 4 levels of phosphate according to L_<16> orthogonal array table on September 19, October 1, 11, and May 1 of the following spring. The results were as follows: 1) In test 1, both seed mixtures of Senpoku-du Puits and Kitamidori-du Puits established sufficient numbers of stands after wintering and yielded a reasonable amount of forage. Although the wintering ability of the seedlings and the forage productivity in the case of the seeding on October 8 were inferior than the ones for the seeding on September 28. 2) In test 2, each component of the Senpoku-Vernal mixture showed superior wintering ability even in the case of the seeding on October 11. However, the seeding after October were found to winter unsuccessfully for both components of the Kitamidori-Thor mixture. 3) An approximate 20Kg application of phosphate per 10 ares as a basal fertilizer was effective for the wintering of the seedlings and the forage productivity of the mixture components, especially for the alfalfa component, provided that the mixtures were seeded by late September. 4) The effect of Mammoth-Italian B as a nurse crop was negative and rather competitive with the components of the mixtures.

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A series of field experiments was undertaken to clarify the changes in structures of a pasture ecosystem due to cessation of grazing. This report deals with the changes of vegetational structures of the following three experimental plots ; Control plot: managed by rotational grazing ; Exclosure-Ca plot: no grazing from 1976 to 1982, with lime (CaCO_3, 2ton/ha) application at the beginning of the period ; Exclosure-non. Ca plot: no grazing during the same period without application of lime. Results were summarized as follows: 1. The number of plant species observed in both the exclosure plots decreased until the fourth year of the period, but increased twice as many as that in the control plot by invasion of various species after the fifth year. Consequently, the plant species diversity of commmunities represented by the number of species and Raunkiear's life-form classification increased in both the exclosure plots compared with that in the control plot. 2. The dominant species indicated by summed dominance ratio (SDR_2) was Dactylis glomerata during the experimental period in all the plots, but SDR_2 of some epigeals such as Sasa nipponica and Querucus spp. increased from the fifth year in both the exclosure plots. 3. Aboveground biomass increased until the third year and stabilized at the about 1300g/m^2 dry matter from the fourth year in both the exclosure plots. 4. There were little differences in vegetational structures between the exclosure plots. The results were discussed ecologically in relation to the changes of soil conditions.

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Three experiments were conducted to investigate the effectiveness of sodium hydroxide (NaOH) pre-treatment for increasing intake and energy value of ensiled rice straw. In the Experiment 1, chopped rice straw was spray-treated with NaOH at the rates of 0, 3, 6 or 9% of the straw dry matter at the moisture levels of 40, 50, 60 or 70% prior to ensiling. Changes in cell wall constituents, in vitro dry matter disappearance (IVDMD), pH and organic acids were traced until 60th day of ensilage. Intake and digestion trials with goats were conducted with four rice straw silages pretreated with NaOH at the rates of 0, 3, 6 or 9% of dry matter in the Experiment 2 and with two NaOH 6%-treated rice straws ; freshly prepared and ensiled ones in the Experiment 3, respectively. The content of hemicellulose decreased and IVDMD reversely increased with increasing amount of NaOH. The IVDMD increased during storage in the silages pre-treated with NaOH at the rates of 3-9% of dry matter. The pH of the straws increased with increasing amount of NaOH, although it decreased during storage. The content of total organic acids was the highest in the silage pre-treated with NaOH at the rate of 3% and decreased beyond that rate. It increased with increasing level of moisture at every level of NaOH. Acetic acid increased in the silages pre-treated with NaOH at the rates of 3-9%. Lactic acid decreased in the silages pre-treated with NaOH at the rates of 6 and 9% in this order, and butyric acid was not present in these silages. The daily dry matter intakes were 22.3, 34.7, 45.3 and 37.4g/w^0.75kg for the NaOH 0, 3, 6 and 9%-treated silages, respectively. The digestibilities of dry matter, organic matter, NFE, crude fiber, NDF, ADF, hemicellulose and cellulose markedly increased with increasing amount of NaOH up to the level of 6% and slowed down thereafter. The TDNs of silages were 37.8, 50.2, 56.8 and 56.1% for the NaOH 0, 3, 6 and 9%-treated silages, respectively. The daily dry matter intakes were 42.4 and 51.8g/w^0.75kg for the freshly prepared and the ensiled straws, respectively. The digestibilities of fibrous constituents were significantly higher for the ensiled than the freshly prepared. The TDNs of straws were 54.4 and 57.5% for the freshly prepared and the ensiled ones, respectively. From these results it was concluded that the spray-treatment of rice straw with NaOH prior to ensiling was effective for increasing intake and energy value of rice straw silage and the optimum amount of NaOH for treatment would appear to be 6% of the straw dry matter. Ensiling after treatment resulted in a decrease of pH, satisfactory preservation during the ensiling period and increases in intake and energy value of rice straw. Consequently, ensiling was a practical and useful method for utilizing rice straw treated with NaOH.

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This experiment was undertaken to investigate the effect of pre-harvest application of fertilizer nitrogen to summer aftermath on yields and chemical compositions of summer and autumn aftermaths. On orchardgrass and meadow fescue swards, summer aftermaths (2nd growth) were harvested on 18 August and 8kg N per 10 are as urea was given (a) 10 days before, (b) immediately after and (c) 10 days after the harvesting time. Herbage samples were taken for yield and chemical analyses at intervals of about 10 days from 9 August to 31 October. 1. Dry matter yields of summer aftermath were increased by pre-harvest application of N and those of autumn aftermath were higher in just after application of N compared with pre- and post-harvest application of N. There was no difference on overall yields for autumn aftermath plus summer aftermath between treatments (a) and (b). Orchardgrass swards had many heading stems and produced higher dry matter yields than meadow fescue swards. 2. Of chemical compositions of summer aftermath, crude protein contents were increased from 12 to 20% in both swards and crude fiber contents were decreased from 37 to 31% in orchardgrass and from 33 to 28% in meadow fescue by application of N 10 days before harvest. 3. In each treatment of both swards, crude protein contents of autumn aftermath increased rapidly till 10-20 days after each fertilizing time, reaching peak values of around 30% in dry matter basis and then decreased steadily. Pre-harvest application of N to summer aftermath advanced the time of the beginning to decrease crude protein contents and lowered final contents of autumn aftermath by 4-6% compared with other treatments. 4. Contents of nitrogen free extract of autumn aftermath in pre-harvest application of N increased without depression after harvest of summer aftermath, but those in immediately after and 10 days after applications decreased largely once after harvest and then increased gradually. Consequently, contents of nitrogen free extract in pre-harvest application were consistently higher at levels of several percentages than those in other treatments and finally reached to a high content of 60% in dry matter basis. From the above results, it is suggested that pre-harvest application of N to summer aftermath improve yields and nutritive values of summer aftermath and result in "low protein but high energy content" of autumn aftermath.

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