Dry matter (DM) production, change in botanical composition and viability of mulberry, and growth of mulberry main trunk diameters in mulberry-pasture association subject to harvesting were determined from 1997 to 2000. Mulberries in the association were planted at a spacing of 3m between rows and 0.7m between plants (4,762 plants/ha). A mixture of five temperate species was sown among mulberries rows. The association was compared with a sward and mulberry in pure stands. Sward and mulberry were harvested five and three times per year, respectively. Yearly DM production in mulberry-pasture association showed increases of 13% and 237% in 1997, 32% and 192% in 1998, 57% and 189% in 1999, and 34% and 380% in 2000 over the sward and the mulberry in pure stands, respectively. It was confirmed that the mulberry-pasture association system has very high potential for forage productivity. Moreover the seasonal forage production in the association was more even than that in sward due to the contribution of summer-autumn production of mulberry. Weeds and white clover in the sward increased over the duration of the study, while the association maintained the vegetational condition relatively well. Although mulberry maintained a high viability of 97-100% over the four years in spite of being harvested three times per year, the vigor of these mulberries seemed to be weakened by the high harvesting frequency.

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Exogenously applied gibberellic acid, cytokinins and cyclic adenosine monophosphate (cAMP) are known to enhance phleinase induction in stem bases of orchardgrass, while abscisic acid (ABA) to suppress, and auxin and ethylene to have no influence on it in our previous study (Yamamoto and Mino, 1998). The present study measured the changes in levels of the bioactive substances in stem bases of orchardgrass after defoliation. Free gibberellin activity in the stem bases decreased after defoliation, and the bound one remained unchanged. No significant change in ABA activity was detected in the defoliated stem bases. Cytokinin activity and zeatin concentration decreased after defoliation. cAMP concentration also decreased after defoliation. All the directions of these changes were contradictory to the idea that these bioactive substances are involved in phleinase induction in the stem bases of orchardgrass after defoliation.

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Carbon dioxide (CO_2) is well known to be a "greenhouse gas" which is capable of causing significant climatic changes. The optimum ranges in the growing area of grass species will likely shift as a result of climatic changes, and there will be corresponding changes in the vegetation zones here in Japan. It is therefore necessary to determine the optimum range for each species that will grow in the new vegetation zones expected from the result by the climatic changes. We measured the effect of increasing CO_2 concentration and leaf temperature on the net photosynthetic rate (Pn) of tall fescue. Tall fescue (Festuca arundinacea Schreb. cv. Nanryo) was grown in 1/5000a Wagner pots in two phytotrons with inflow CO_2 concentrations of 350 ppm and 700 ppm. Pn was measured under different environmental conditions. Six different leaf temperatures (15°, 20°, 25°, 30°, 33° and 35℃) and 8 different CO_2 concentrations (0, 30, 100, 200, 350, 500, 700 and 1,000 ppm) were set for each tiller (grown in CO_2 concentration of either 350 or 700 ppm). The results showed that Pn increased with CO_2 concentration below 500 ppm at each temperature, and decreased with CO_2 concentrations above 700 ppm at leaf temperatures of 15, 20 and 25℃. The rate of decrease in Pn of tillers grown in 350 ppm was higher than that of tillers grown in 700 ppm. In order to examine the effect of doubling CO_2 concentration, the Pn was regressed by the quadratic of leaf temperature. The effect of the increase in CO_2 concentration on the relative photosynthetic ratios was calculated for each temperature, and the relationship between the relative photosynthetic ratio and leaf temperature was examined. The relative ratio was found to increase with rising leaf temperature. According to this relation, both of the examined parameters expected to increase with global warming, i.e. temperature and CO_2 concentration, would have positive effects on the growth of tall fescue.

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Effects of forest litter on the growth of Zoysia japonica Steud. were examined by a greenhouse experiment. Three litter treatments were conducted to Z. japonica sods planted into pots : with leaf litter of deciduous trees, with plant ash, and without both litter and ash (as control). The litter or ash was spread over the soil surface. The dry weights (DW) of stolons and erect stems of Z. japonica were not significantly different between the plots. In contrast, the root DW was lower for the leaf litter plot than for the control. The soil moisture contents were not significantly different between the plots. On the other hand, the nitrogen contents of stolons and erect stems were slightly higher for the leaf litter and ash plots than for the control. Soil day temperature in fine weather(with>5 hours sunshine) increased for the ash plot, while it declined for the litter plot. However, night soil temperature did not largely declined for the litter plot. Thus, it seemed that leaf litter lowered soil temperature of day and raised soil temperature of night, thereby the root growth of Z. japonica was suppressed, but the growth of stolons and erect stems was not affect. The application of the ash raised the soil temperature of the day, but not affect the growth of Z. japonica.

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We studied effects of stocking rate and initiation date on the annual herbage utilization in grazed sward through two grazing seasons. In the two experimental pastures with the area of 0.935 ha, five and seven lactating dairy cows were grazed rotationally for 5 hours everyday from May to October (G5 and G7, respectively). The initiation date was May 1st at 1995 and May 20th at 1996. The herbage regrowth and intake were estimated from herbage-mass measured before and after grazing. Annual mean grass-height before grazing (GH) were 17.6 and 26.4 cm in G5, and 15.4 and 22.3 cm in G7 in year order. Total amounts of herbage regrowth over the grazing season (HR) were 7.0 and 5.8 t DM/ha in G5, and 7.8 and 6.5t DM/ha in G7 in year order. Herbage production, consist ing of herbage growth before grazing season and HR, amounted to 7.5 and 8.0 t DM/ha in G5, and 8.4 and 8.6 t DM/ ha in G7. Annual herbage utilization (HU) was 7.2 and 7.2t DM/ha in G5, and 8.2 and 7.8 t DM/ha in G7. Grazing in high stocking rate or early start of grazing made GH being low but HR and HU being high.

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Seasonal changes in dry matter yield and botanical composition of timothy and meadow fescue swards were investigated for three years through five or six times of defoliation per year. Timothy cv. "Hokushu" and meadow fescue cv. "Tomosakae" swards established with or without white clover cv. "WWV-14" were studied. They were broadcasted in mixed sown sward and sown stripe (row space was 30 cm) in pure one. Weeding was carried out continuously in pure sward through this study. In pure sward, there had been no lost plants observed, and the tiller number per square meter at the defoliation time were preserved around 2,000 or more in both grass species untill the fourth year after the establishment. While the depression of dry matter yield of grass in mixed sward as compared with pure one was obviously recognized and the degree of them was higher in timothy than meadow fescue. On the contrary, the ratio of legume became higher in timothy sward. Those differences between grasses became remarkable after July (the fourth aftermath in this study) in the third year after the establishment. And these differences were principally caused by the diminishing of grass coverage, not by the plant length of them. Difference of the seasonal changes in dry matter yield between timothy and meadow fescue in mixed sward was not able to be clearly related to ridge breadth, plant length elongation per day, crop growth rate, dry weight of stubble, percent and amount of non-structural carbohydrate or nitrogen of stubble of each grass examined in pure sward. However, those were suggested to be brought about by the specificity of tiller arrangements for regrowth after the defoliation. That is to say, rate of internode-elongated tillers of timothy at the third aftermath (growing season from June to July), which expected to give some effects on regrowth of the fourth aftermath (growing season from July to August), was higher than meadow fescue. Vegetative tiller number which was able to regrow after the defoliation was lower in timothy, and the dry weight of vegetative tillers was also lower in timothy compared to meadow fescue. As a result of such differences in regrowth, the competition ability of timothy against to white clover was guessed to be inferior to meadow fescue then. Therefore success or failure in maintenance of tiller number in July causes critical effect on the foliage productivity after then was concluded.

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We conducted a study of genetic relationships among introduced lines of napiergrass (Pennisetum purpureum Schumach.) based on random amplified polymorphic DNAs (RAPD) analysis. Fifteen lines of napiergrass, which included one interspecific hybrid (P. americanum (L.) Leeke× P. purpureum Schum.) and one dwarf line,were used in this study. From the forty-decamer random primers used, 132 RAPD bands were scored, of which 112 (84.8%) were polymorphic. Twenty one primers resulted in no detected amplification. Three primers produced specific banding patterns that were useful in an identification of these lines. Cluster analysis based on the 132 RAPD bands revealed that the fifteen lines were classified into six groups as reflected in their origin. It was suggested that RAPD analysis could be a useful tool for detailed genetic characterization in napiergrass.

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A dynamic simulation model to predict growth of forage maize is built on a daily time step. The key factors for growth rate in the model are the weather variables of daily solar radiation and air temperature. The daily photosynthetic rate of the canopy is calculated by the equations, which are formulated by the factors of the two weather variables, of development stage (development index) and of the leaf area index. The photosynthetic product is partitioned into leaves, stems, ears, and root system according to the development index. Each organ is respired depending on the air temperature and the stage of the development index. The parameters of the model were determined by data from the cultivar `Takanewase', which were grown for four years in northern, central and southern locations in Japan. The output from the model showed good agreement with the data sets that were not used in the parameter determination. The regression coefficient of predicted biomass to the observed biomass through the origin for leaves stems, ears and aboveground total by a single regression are 1.034, 0.951, 0.954, and 0.965, respectively. When the model was applied to the cultivar `P3715', it was necessary for some parameters to be modified. They were the parameters representing the relationships between temperature and the development index, between partitioning rate of reserves and the development index, and between the specific leaf area index and the development index, and also the parameter of maximum photosynthetic rate. After changing these parameters, there was close agreement between observed and predicted aboveground biomass.

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[in Japanese]

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