In previous papers, we selected some warm season forage plants having a higher tolerance to the water stress (drought) condition. These plants were able to absorb nutrient and water effectively even under the water stress condition. The vigorous growth of root system and the water potential depression in leaves under the water stress condition were contributive to the water stress tolerance in plants. In this study, the water stress tolerance was further analyzed in relation to the changes of osmotic potential in various plant parts, root development and root pressure of rhodesgrass (Chloris gayana Kunth.), sorghum (Sorghum bicolor Moench) and job's tears (Coix lacrymaobi L. var. mayuen (Roman.) Stapf) grown under the water stress condition. The results obtained are as follows. (1) The osmotic potential in each species decreased by the water stress, especially remarkable in rhodesgrass. (2) Total root length and root surface area of rhodesgrass was five to six and three to four time as large as those of job's tears under the water stress condition, respectively. (3) The root development of job's tears was seriously inhibited by the water stress, but the penetration and development of rhodesgrass root was not depressed in deeper soil layer under the water stress condition. (4) The root pressure increased in rhodesgrass with the increase of water stress, but apparently decreased in job's tears. From the results obtained here, it was assumed that the high water and nutrient absorption abilities of grasses being tolelant to the water stress are depending on (1) their higher water absorption potentials resulted with decreasing osmotic potentials of their stems and leaves, (2) the vigorous growth of their roots into deeper soil layer, and also (3) the efficient movement of water and nutrient by increasing their root pressure under the less soil miosture condition.

View full abstract

The growth of Sasa nipponica (Makino) Makino and Sasa borealis (Hack.) Makino on the floor of deciduous forest on the south slope of Mt. Asama was analyzed from seasonal changes of light intensity in the forest and of their leaf area indeces, and light response curve of photosynthesis in both Sasa plant leaves. The relative light intensity below the deciduous forest canopy had a seasonal change following a curve that reached a bottom in summer and showed a plateau from late autumn to spring. The light condition at habitat of S. borealis in the forest was far less favourable than that of S. nipponica. The biomass of S. nipponica increased with increasing light intensity, while that of S. borealis increased with decreasing light intensity in the deciduous forest. The photosynthetic light response curve of S. borealis followed a pattern as generally shown in shade leaf (a low Pmax and low light saturation point). The leaf area index of S. nipponica increased in summer and decreased in winter, while that of S. borealis was almost constant throughout the four seasons. From the facts mentioned above, it can be said that S. nipponica has a higher productivity at the outside than inside of the deciduous forest, while S. borealis can keep a comparably high productivity even inside the forest. Therefore, the habitat isolation of both Sasa species may have been caused by the interspecific difference in dry matter production.

View full abstract

Variation of root system in seedlings and adult plants of tall fescue (F. arundinacea Schreb.) was examined in relation to shoot system. Cultivars tended to show higher shoot growth relative to root growth than natural strains during seedling growth. Among natural strains, those from cool climates tended to have higher root: shoot ratio than those from warm climates. Plants with large tillers tended to have high root DW, but those with rapid rate of tillering tended to have low root DW. During reproductive growth stage, the growth of reproductive tillers did not bring about the proportional increase in root growth, but it caused change in the vertical distribution pattern of roots in the soil: the relatively greater spread of the root in the deeper soil layers.

View full abstract

A 4-year field experiment was conducted to evaluate the contribution of naturally reseeded plants to the density and production of eight temperate grass swards. The experiment employed a split-split plot design with natural reseeding treatments (reseeding, non-reseeding) as the main block, cutting treatments in spring with control as sub plots and kind of grasses as sub-sub plots. In non-reseeding treatment, the reseeded seedlings were removed as early as possible. The cutting treatments were: a) uncutting from early spring until early August (So) and b) uncutting until early August after cutting in late April or early May (S_1). Grasses used were orchardgrass (cv. Potomac, Akimidori, S143), tall fescue (cv. Kentucky 31), Kentucky bluegrass (cv. Baron), perennial ryegrass, Smooth bromegrass (cv. Carlton) and red top. Two years after rexeeding, the whole plots were harvested with five cuttings a year at the same dates in 1981-'82. The differences in yield and tiller density between reseeding treatment and non-reseeding treatment were regarded as the contribution of natural reseeding. The results obtained were summarized as follows: 1) The number of dead plants increased in most species under deferred cutting in spring for two successive years. 2) Naturally reseeded plots had more tillers than the plots whose seedlings had been removed. The difference in the number of tillers between reseeded plots and removed plots was more remarkable in So than in S_1. 3) Dry matter yield in reseeded plots was significantly higher than in removed plots, and it increased remarkably under deferred cutting in spring (S_0). 4) In So plot with many naturally reseeded seedlings, the contribution of the seedlings in dry matter yield to the total sward was 29-36% on the average in all species. Seedlings of perennial ryegrass showed the highest ratio (51-62%) of all species examined. 5) From these results, it was concluded that naturally reseeded seedlings contributed to the increace in the density and production of existing grass swards. In practice, the swards should not be utilized in spring to assure the effect of the natural reseeding. It seems that perennial ryegrass and orchardgrass might be suitable for natural reseeding.

View full abstract

Although grasses of the short grass type are more suitable for grazed pastures than those of the tall grass type, there are not so many reports about dry matter production in the grazed pasture of the short grass type. The purposes of this study are to clarify (1) the seasonal change of dry matter production and (2) the effect of the heavy rate application of nitrogen on dry matter production and annual net production in the grazed pasture of Agrostis alba L. (redtop) as the short grass type. The grazing experiment was carried out in the Experiment Station on Highland Animal Production, Kitashitara, Aichi in 1979, 1980 and 1981. The weather data measured in this station are as follows (Fig.1). Annual mean air temperature, rainfall and mean solar radiation are 10.3℃, 2800mm and 3000kcal/m^2/day, respectively. The experimental pasture was divided into ten paddocks, and the area of each paddock was 0.3ha. In 1979 and 1980, the five paddocks (as the CN plot) were applied with the conventional rate of nitrogen, phosphorus and potassium (N: 290, P_2O_5: 230, K_2O: 280kg/ha/year), and the rest five paddocks (as the HN plot) were applied with the same rate except nitrogen (810kg/ha/year). Two herds of six steers were used for the grazing experiment. One of them grazed in the CN plot, the other did in the HN plot. In 1981, both plots were applied with the lower rate (N: 110, P_2O_5: 50, K_2O: 50kg/ha/year), and one herd of eight steers grazed both plots in turn. The rotations were six times in 1979 and 1980, and five times in 1981. Biomass of grasses and separated parts as leaf, stem, standing dead and underground were measured at the end of each grazing period in the rotation from May to October, and also in March, April and November. In each period in the rotation, six movable protect cages were used to protect from grazing by steers. Aboveground part was cut at the height of 3cm from ground with the 1m^2 quadrat both in and out of the cages. Only out of the cages, biomass of stubble (0-3cm) was sampled with the 1/16m^2 quadrat. Surface litter was sampled at the same place. After that, underground part was sampled to 15cm depth also at the same place. Results obtained were as follows. The seasonal change of total biomass (Fig.2) was mainly affected by that of underground rather than that of aboveground. The total biomass attained its maximum (1200g/m^2) in May in 1979, but in April in 1980. This value was nearly same to that of orchardgrass pastures (750-1370g/m^2). The seasonal change of above-ground living biomass (Fig.3) was affected by that of stem biomass (60-380g/m^2) rather than that of leaf biomass (30-170g/m^2). The seasonal change of underground biomass varied with years. Biomass of underground attained its maximum (about 800g/m^2) in July in 1979, but in April in 1980. The quantity of standing dead (Fig.4) was very low (25-50g/m^2) through the grazing period, though it was high in spring (200-250g/m^2) and in autumn (150-170g/m^2). Biomass of surface litter was 100-350g/m^2 (Fig.4). Biomass of underground in the HN plot was significantly higher (p<0.05) than those in the CN plot for the effect of the heavy rate application of nitrogen. Biomass of other parts in the HN plot was also higher than those in the CN plot, but the differences were not significant. Annual net production (Table 1) in the CN plot were 930g/m^2 in 1979, 960g/m^2 in 1980 and 870g/m^2 in 1981, respectively. Those in the HN plot were 1140g/m^2 in 1979, 1000g/m^2 in 1980 and 1290g/m^2 in 1981, respectively. It was mainly affected by the amount of intake by steers and net production of underground. Annual net production in the grazed redtop pasture was higher than that in the Zoysia type pasture (500g/m^2), but lower than that in the tall fescue (1650g/m^2) or the orchardgrass pastures (1200-1450g/m^2).

View full abstract

A series of the trials were carried out over a ten-year period to investigate the voluntary intake and digestibility of alfalfa (Saranac) clipped at several growth stages and fed to wethers. The samples consisted of 18 first cutting and 37 aftermaths. Relationships between the cutting dats and the nutritive value or voluntary intake were estimated. In the first crops, there were highly significant correlations between the number of days to harvest from April 30 (X) and DCP or TDN content. The regression equation was shown as DCP=26.4-0.21X (r=-0.89, p<0.01), while TDN=84.2-0.46X (r=-0.89, p<0.01). However there was not significant correlation between the cutting dates and voluntary day matter intake. In the second crops, the relations between the regrowth period (X) and TDN content was shown as TDN=67.0-0.22X (r=-0.62, p<0.01), while relations between X and the voluntary day matter intake (VI: g/kg^<0.75>) was shown as VI=127.2-1.15X (r=-0.71, p<0.01). The last crops showed the much slower rate of fall in the digestibility and voluntary intake than that noted above.

View full abstract

A series of trials has been carried out over a nine-year period to determine the level of voluntary intake and digestibility of clipped orchardgrass fed at several growth stages to wethers. The samples consisted of 31 first cuttings and 71 aftermaths. Forage and feces were fractionated into cell wall (CW) and cell content (CC) with neutral detergent solution, then digestibility of CW, CC and their digestible amount were determined. The change in the amount of digestible dry matter (DDM) in grass was related to the amount of digestible CC and indigestible CW, however, digestible CW was observed to have little relation. Fecal CW excretion (g/day/kg^<0.75>) in their full intake was abut 13g, varied little between the first cutting in spring and aftermath. Fecal CW excretion was not significantly correlated to voluntary dry matter intake (VI), but there was a significant correlation between fecal CC excretion and VI. An average true digestibility of CC was 98%, and the endogenous and becterial excretion of dry matter amounted to an average of 14% of VI. These data are consistent with the theory that indigestible CW inhibit VI and voluntary nutrient intake.

View full abstract

Since the previous work has indicated that nitrogenous constituents of growing herbage are easily degradable by rumen microorganisms and liberate an excessive amount of ammonia, the present experiment was carried out with an in vitro study to clarify the effective carbohydrate or lipid material for microbial utilization of rumen ammonia at the circumstance of herbage feeding. The effect of various carbohydrates on the microbial uptake of ammonia left in strained rumen fluid was observed in vitro by 1hr incubation. In the case of monosaccharide supply, galactose, arabinose and xylose were more effective than glucose, mannose and fructose. Among the disaccharides supplied, cellobiose was superior than maltose and sucrose. Trehalose had a little effect. Among the polysaccharides used, cellulose showed no effect while corn starch and pectin showed a little effect. On the other hand, xylan and inulin lowered considerably the ammonia concentration. Xylan was the most effective polysaccharide. The extent of VFA production was correlated with that of ammonia disappearance. The experiment was subsequently undertake to examine the effects of two polysaccharides (starch and xylan) and two lipid materials (corn oil and corn 'oil foots') on microbial utilization of ammonia which derived from the ruminal degradation of freeze-dried Italian ryegrass. The addition of corn oil did not show any effectiveness for ammonia utilization during 2hr incubation. Xylan, corn 'oil foots' and corn starch, in order of their effectiveness, tended to depress the ammonia release. In the case of xylan addition, the ammonia release decreased to 71%. Although these additives increased VFA production more or less, xylan was superior for VFA production. Effect on pH change was largest in xylan addition. Gas production was also mostly enhanced by xylan addition. The superiority of xylan over corn starch was further examined with not only strained rumen fluid but also whole rumen digesta. The effect of xylan was discussed from the stand point of the function of microbial population in the rumen of herbage-fed animal.

View full abstract

This study was carried out to investigate heat damage in roughage from a viewpoint of relationship between treated temperature and changes in acid detergent insoluble nitrogen (ADIN), neutral detergent insoluble nitrogen (NDIN) and carbohydrates. The first crop of Italian ryegrass was used for Expt.1 and aftermath (2nd crop) for Expt.2. Materials dried with aeration at 5 levels of temperature (40, 60, 80, 100 and 120℃) and low moisture silages ensiled at 2 levels of temperature (20 and 60℃) were prepared. 1. ADIN contents (% of total nitrogen) in materials dried with aeration were highest at 120℃, which showed 16% and 14% in comparison with 4% and 10% at freeze dried materials (Expt.1 and Expt.2, respectively). ADIN contents in materials dried with aeration at 120℃ were increased with addition of glucose. In low moisture silages, ADIN contents were increased with advancing period of ensiling at 60℃, showing 13% and 20% compared with 4% and 13% at ensiled materials (Expt.1 and Expt.2, respectively). 2. As for changes in structural carbohydrates in materials dried with aeration, NDF and hemicellulose contents were increased with temperature, while ADF and lignin contents were high at 120℃. Lignin contents in materials dried with aeration at 120℃ were increased with addition of glucose. In low moisture silages, lignin contents were higher at 60℃ than at 20℃. 3. Mono, Oligosaccharides contents in materials dried with aeration tended to decrease at 120℃. In low moisture silages, those contents were decreased with advancing period of ensiling at 20℃ and 60℃, but the degree of decrease was marked at 20℃. 4. From the above results, heating with aeration under 60℃ makes no difference in ADIN and carbohydrates contents, but over 80℃, ADIN, NDIN and lignin contents are increased and mono, oligosaccharides are decreased. And it is recognized at early stage after ensiling at 60℃ that low moisture silages accompanied with fermentation have the same changes in chemical components as materials dried with aeration at high temperature.

View full abstract

The questionnaire was conducted on 348 public pastures in the snowy area to investigate the general conditions and the pasture facilities. These pastures mainly managed by municipalities, and 77% of the purpose of management was the diposition of cattle. Although the public pasture establishment have become popular from 1965, these pastures were mostly situated on the rugged area, and recently developed in the highland such as Kitakami or Abukuma mountainous area. The grazing season was mainly influenced not only by the latitude of these pastures but also by the altitude of them, and became shorter as the altitude of pasture became higher (Figs.3 and 4). 5% of pastures in Hokkaido have more than 1000ha of the area and 22% of pastures have more than 300ha, but only 16% of pastures in the prefectures have more than 300ha of the area. The area of native grasslands in public pasture was not so small. As the area of pasture became wider, the number of cattle increased although they must have the longer line of fences to graze them (Fig.6). The percentage of the fence maintenance cost in the pasture management cost became smaller as the area of pasture became wider. These parcentage of the fence maintenance cost were more than 15% of the pasture management cost in 0-500ha of the area of pasture, more than 10% in 500-1000ha and less than 5% in more than 1000ha pasture (Fig.5). It was common that one person or one pasture emplyee has managed cattle and fences usually and that above 100 temporary employees have repaired the fences before or after grazing season. In the cattle management, the attentions were paid for the cattle's escape from fences and the disease or the accident of cattle. Cattle escape was generally caused in the fence line with an inclination or beside a swampland and in the fence with loosening the wire. The method driving the cattle to another enclosed pasture was mostly by the man, sometimes with using the opportunity of cattle gathering to the watering facility to drink a water. It is suggested that applying better fence structure or better construction method of fences is important for the cattle management.

View full abstract

The questionnaire was conducted on 348 public pastures in the snowy area to investigate the conditions of the fences and watering facilities. Concerning to the fence materials, 92% of farms use the steel fences. The steel posts have enough galvanizing on the their surfaces and hardly have the problem of the durability. However the wire, which 91% of them was barbed wire, was easily rusted because of thin zinc coating and it was hardly known that there were several kinds of wires depending on the minimum zinc coating weights. Concerning to the fence structure, the posts constructed with 4m apart were found in 60% of farms. 37% of farms had 4-wire fence, 21% of them had 3-wire fence and the width of wire row was about 30cm in 4-wire fence and 36-38cm in 3-wire fence, and the height of the top wire was about 120cm. The length of post was almost 1.8m and the penetration depth under the ground was mostly one third of the post's length. In one third of farms props were fixed in the ratio of one prop to 10 posts, and it was necessary to fix the props on the fence line such as the corner of fences, or the soft and uneven ground where posts were easy to tip. The problems on the fence management were found mainly in the wire or the wiring method rather than posts. Since the wire was broken and became rusty, the wire was mostly renewed after 5-6 years. Then the wiring method had several problems such as the expensive labor cost or the shortage of labor at the time of fence maintenance. And the wire, posts or wire fittings had several problems for themselves. The snow damage to the fences was found in 71% of farms, and these were mainly found as the defects of the posts and the breaking of wire in the place where the snow abounded in pastures. For protection from the snow damage, the wire were taken off or posts were pulled out in many farms. In particular the posts were damaged on the slopy, uneven or cliffy ground. For planning the fence in the snowy area, it is necessary to adopt the construction method corresponded to the topographical, meteorological and ground conditions to keep the fences from damage by the snow. 60% of farms used the water of river or stream as the source of the watering facilities. These facilities, constructed separately in one elclosed pasture, were found in 46% of farms, and 28% of them placed one watering facility between two enclosed pasture jointly. Then 27% of them constructed these facilities in an intersecting point among eclosed pastures. In the latter case, using the opportunity of cattle gathered to the watering facility becomes a laborsaving method for the cattle driving.

View full abstract

[in Japanese]

View full abstract