In this report, potassium leaching from some species of forages was investigated. The results obtained are as follows; 1. Potassium contents in dewdrops on forage leaves were in the ranges of 4-77ppm, and the values were markedly higher than those in raindrops. 2. Extractable potassium in forage leaves and the ratio of extractable potassium to the total potassium examined under submerged condition were in the ranges of 32-81mg/100g fresh weight and of 2.5-10.4 per cent, respectively. The liability for potassium leaching from living forage was ranked as follows ; dead leaves>over-mature leaves>mature leaves>immature leaves>stem and ear or flower. 3. Potassium in forage leaves extracted into running water was in the ranges of 1/20-1/4 as compared with that extracted under submerged condition. In addition, a little difference of leaching pattern between graminous forages and leguminous ones was observed. That is, graminous forages were likely to leach the most parts of their extractable potassium immediately after running water extraction began, while leguminous forages lost their extractable potassium with elapse of extraction time. 4. From this investigation, it was confirmed that a closed recycle system of potassium exists in grassland ecosystems. The nutritional and ecological significance of the closed recycle system on potassium behavior in grasslands is now under investigation.

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The degree of frost hardiness, the carbohydrates content, and the degree of resistance to Sclerotinia snow blight disease (Scleotinia borealis Buback & Vleugel) were compared in eastern Hokkaido among 27 cultivars collected from various geographical regions. The frost hardiness of seedlings of cultivars determined by the artifical crown freezing method in the beginning of winter, were positively correlated with the mean temperature in January of their breeding sites (r=-0.707). The increasing order of content of carbohydrates fractions accumulated in seedling, was reducing sugars (RS)<nonreducing sugars (NS)<total sugars (TS)<Fructosans (FS)<water soluble carbohydrates (WSC: TS+FS). All of these fractions except the RS showed significant correlations with both of the frost hardiness and the dry matter percentage. Higher correlation coefficients were obtained between the WSC content and the frost hardiness (r=+0.673), and between the WSC content and the dry matter percentage (r=+0.710). Resistance to Sclerotinia snow blight disease of mature plants of 17 cultivars was evaluated at the end of snow cover with the percentage of tillers which were damaged by Sclerotinia. The percentage of the damaged showed significant negative correlation with the frost hardiness (r=-0.617), the NS content, the TS content, the FS content and the WSC content (r=-0.657). North European, North American and Hokkaido cultivars were more resistant to Sclerotinia snow blight disease than others. The WSC content seemed to be a useful measure both in breeding of winter hardy cultivars and in cultivation of orchardgrass of soil freezing area, and the dry matter percentage could be used as a measure of the WSC content.

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Ramets of perennial ryegrass (PRG), Lolium perenne and tall fescue (TF), Festuca arundinacea were transplanted with 10cm spacing in hard plastic boxes 61×41×32 deep in such a way that the two species were grown in a single culture (S) and in their equal mixture (M) in order to estimate the effects of top or shoot competition and of root composition separately by the partition technique. Transparent, hard plastic panels were placed above the ground and/or inserted into the soil to the full depth of the box, thus the four competition-forms, full competition (FC), top competition (TC), root competition (RC) and no competition (NC) being used (Fig.1). In each competition-form, two boxes were used for single culture of each species and the other two were for their mixture. Tiller number, LAI, top dry matter yield and plant height were measured five times (C_1〜C_5) in each 1978 and 1979. In FC and RC, in general, tiller number, LAI and DM yield of PRG were higher in mixed culture than in single culture, while those of TF were lower in mixed culture than in single culture. In TC, however, such patterns as found in the above two forms were not always detected (Tables 1 and 2). Plant height did not show any significant difference between the two cultures, although tiller number and DM yield did so except spring (C_1, C_2) of 1978 (Tables 3 and 4). In other words, tiller number and DM yield were clearly affected by competition, and plant height, in contrast, was not. Thus, the quantitative characters except plant height biased positively in the aggressor species, PRG and negatively in the suppressed species, TF (Table 5). In 1978, PRG might be superior in plant height to TF except heading time of TF (C_2), but in 1979 the superiority of PRG was likely displaced by TF (Table 3), probably due to an uncertain relation in superiority of height between the two species. In the previous reports by the present authors (YAMADA et al. 1981, and SATO et al. 1982), however, little significant difference of plant height had been shown between PRG and TF. Thus, in the present report plant height may be considered to be not so operative as a competitive ability. Therefore, instead of plant height, root characters such as root length, root number and root weight may be considered to play a major role to control the competition. These results likely suggest that the overall competition between the two species might depend largely on root competition.

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A field defoliation experiment of Zoysia japonica was conducted in relation to competition and soil condition. Cumulative leaf length (CLL) of tillers (ramets) following the defoliation was measured at five-day intervals and at three different positions on the hillslope of Mt. Azuma, Hiroshima Prefecture. The plants for the experiment were subjected to four treatments with a combination of defoliatiation and non-defoliation on the tillers of Z. japonica under full and reduced competition. The CLL of tillers under reduced competition were significantly higher than that under full competition. In comparison between the defoliated and undefoliated tillers under reduced competition, the former exhibited significantly (P<0.01) higher CLL than the latter in the upland position. This trend was, however, indistinct at the lowland position. The new leaf emergence was delayed under full competition. The results indicate that effects of defoliation on the tillers of Z. japonica were altered by the stress of competition with other plants. Regrowth of Z. japonica was also discussed in relation to its physiological function as a C_4 plant and soil condition.

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Sorghum species shows high productivity in the warm region of Japan. To evaluate the possibility of its introduction to the northern part of Japan, the dry matter production and growing behavior of sorghum species were investigated. 36 cultivars were grown on the alluvial soil in Sapporo in 1984. Plant characteristics of vegetative growth, floral morphology and dry mater were examined. They were subjected to principal component analysis (PCA) to describe multivariate diversity. The rate of dry matter accumulation was rather Iow during T_1 period (July 20-31), but high during T_2 period (July 31-Aug.13). The maximum rate of dry matter accumulation of high-yielding group during T_2 period was 50.2g/m^2/day. The results from PCA showed that the high-yielding group was characterized by high dry weight of main stem, low-tillering ability and high dry weight per tiller, and that the low-yielding group was characterized by high tillering ability and early flowering.

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This study was conducted to clarify the intra-and interspecific relationships of tetraploid ryegrass cultivars based on the phosphogluco isomerase isozyme (Pgi-2) variation. The leaf materials of 10 tetraploid ryegrass cultivars in the two Lolium species were assayed by the horizontal starch gel electrophoresis for an enzymic system, Pgi-2. The results obtained were as follows. 1. Seven bands were detected on the zymograms of Pgi-2, and 26 phenotypes in the possible 35 phenotypes have been identified by means of the gene dosage effects on the isozyme bands. Besides, four alleles on a locus were confirmed in the tetraploid cultivars. 2. Several different phenotypes were observed in each cultivar. 3. For testing the distinctiveness and the relationships among cultivars in the two species, Nei's genetic distance was applied. As the results, it was suggested that there was distinctive difference of allele frequencies between L. perenne and L. multiflorum. 4. The allele frequencies of the two tetraploid ryegrass species agreed well with those of the diploid ryegrasses reported in the author's previous paper (1985).

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Response to Mo applied of Macroptilium atropurpureum cv. Sitratro was compared in the following aspects ; pot and field experiment, Mo-compounds, Red-Yellow soils derived from different parent materials, and the soils with same parent material from different locations. Results: 1) The pattern of plant response to Mo applied in the pot experiment duplicated that in the field experiment suggesting higher feasibility of a pot experiment for estimating Mo availability in the field conditions. 2) Plant growth was improved with Mo compounds in the following order ; Molybdic acid>Molybdenum powder>Ammonium molybdate>Sodium molybdate. Optimal application rate was at around 30g Mo/10a. 3) Effect of Mo applied to Red-Yellow soil changed with parent materials in the following order ; Sand stone/Mud stone≫Granite>Crystalline schist>Chlorite>Nagura gravel bed. The response in the sandy soil was equivalent to that in the soil derived from Nagula gravel bed. 4) Greater response to Mo applied was observed in the plant growing in the soils at lower elevation than those at higher elevation.

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Ammonia production from nitrogenous compounds of grasses and its uptake by rumen microorganisms were estimated by an in vitro ^<15>N-tracer technique under non-steady-state condition. In the first experiment, 0.5g of 4 different freeze-dried Italian ryegrass samples containing 20.9, 25.2, 31.2 and 36.5mg N/g was incubated for 2 hours with 1.0ml (^<15>NH_4)_2S0_4 (0.42mg N) and 20.0ml rumen fluid obtained from a goat fed on alfalfa hay. Values of ammonia concentration increased during incubation were 13.7, 17.3, 30.4 and 37.2mg N/dl according to the levels of N content of grasses. True ammonia production estimated by ^<15>N-tracer technique showed that the values were 24.1, 26.3, 37.3 and 44.1mg N/dl, respectively. The differences between the values of true ammonia production and the increased values of ammonia concentration were considered to be the values of ammonia uptake by rumen microorganisms. These values were 10.5, 9.0, 6.9 and 6.9mg N/dl, respectively. In the second experiment, 0.5g of freeze-dried Italian ryegrass samples containing low (20.9mg N/g) and high (36.5mg N/g) nitrogen supplemented with 0.1g of either xylan, corn starch or cellobiose was incubated with 20.0ml of rumen fluid for 2 hours. The result showed that ammonia uptake was stimulated by xylan or cellobiose but not by corn starch, and the uptake was specifically greater in the high N grasses. These results suggest that the high N grasses do not sufficiently contain carbohydrates such as xylan and cellobiose which are needed for ammonia utilization by rumen microorganisms.

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A series of trials has been carried out over a ten-year period to determine the level of voluntary intake and digestibility of clipped alfalfa fed at several growth stages to wethers. The samples consisted of 19 first cuttings and 38 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 alfalfa 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 about 18g, varied little between the first cutting in spring and aftermath. An average true digestibility of CC was 96%, and endogenous and bacterial excretion of dry matter amounted to an average of 13% of voluntary intake. One gram of digestible CW was equivalent of 3.73 Calories of digestible energy and one gram of digestible CC was 4.32 Calories.

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[in Japanese]

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Lack of long-term stand persistence has limited the use of red clover (Trifolium pratense L.) in grass-legume mixtures. The non-flowering plants of red clover that do not flower in the seedling year are known to persist longer than the flowering ones. The non-flowering plants develop dense rosettes in the fall of the seedling year, thus they bear a large number of nodes in the crown. Rooting at these nodes is likely to be a factor affecting persistence, because the most persistent plants of red clover consist of clonal plantlets propagated by root development from the crown. The objective of this experiment was to examine the association between the growth type and the habit of root development in the seedling year.

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A stochastic model of dispersion of cattle excreta in pasture was reported in the previous paper. However, limited information is available on the effects of patchily aggregated return of cattle excreta in pasture on herbage yield. Two problems related to these effects are considered in this paper: (1) How do patchily aggregated excreta depress herbage yield in comparison with evenly scattered excreta? (2) How does the number of patches or lumps of excreta per unit area affect herbage yield? The data obtained may afford useful information for the planning of large scale experiments to evaluate the effect of cattle excreta on pasture fertility.

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