@article{oai:repository.naro.go.jp:00001713,
 author = {大谷, 一郎 and OTANI, Ichiro},
 journal = {近畿中国四国農業研究センター研究報告, BULLETIN of THE NATIONAL AGRICULTURAL RESEARCH CENTER for WESTERN REGION},
 month = {Feb},
 note = {Recently, abandoned agricultural lands-particularly terraced paddy fields and forests-have increased in extent in the hilly and mountainous areas of Japan. These abandoned lands can be used without intensive management when they are used as grazing pasture. Japanese lawngrass (Zoysia japonica Steud.), a common species in native Japanese pastures, is known to be useful in this application because it persists without intensive management and alleviates soil erosion by stabilizing soils with its stolons, which densely cover the soil surface. This study was intended to clarify the methods for converting abandoned agricultural lands into Zoysia pasture to support cattle grazing and facilitate improved land use and conversion. The results obtained can be summarized as follows : 1. The influences of groundwater level, shading, and slope aspects on Z. japonica growth were examined. Growth of Z. japonica was more seriously inhibited in the treatment with a 3-cm groundwater level than in the 20-cm treatment. The growth differences among lines were not significant. Under severe shade (26% relative solar radiation), growth was more seriously inhibited than under weak shade (37.2%) and short-day treatments. Growth differences among the lines were recognized in both the weak shade and short-day treatments. The growth of Z. japonica was greater on a gentle slope (15°) than on a steep slope (27°), and was greater on a south-facing slope than on an east- or west-facing slope. On slopes, the stolons of Z. japonica were more numerous growing downward than growing upward. 2. The influences of forest-floor litter and charcoal on Z. japonica growth were examined in a greenhouse experiment. Sod of Z. japonica was grown in pots with three soil-surface treatments : leaf litter of deciduous trees, charcoal, and neither (control). The dry weights of stolons and the number of erect stems of Z. japonica did not differ significantly among the treatments ; however, the root dry weights were lower for the plot with leaf litter than for the control. Leaf litter decreased the soil temperature during the day and retained heat in the soil during the night. The mechanisms for how litter affected the growth of stolons and erect stems of Z. japonica were unclear. The application of charcoal increased the daytime soil temperature, but did not affect the growth of Z. japonica. 3. The effects of spring-sown herbage species on the establishment of Z. japonica were also investigated. Sod of Z. japonica was planted and herbage species were sown in March (sowing treatment). In plots where herbage species were not sown (control), both the frequency and coverage of Z. japonica increased rapidly, reaching 100% in the second year. In contrast, coverage by Z. japonica in the sowing treatments were low (10% to 77.5%) in the first year and increased only slowly in the second year. In the second year, the coverage of Z. japonica in September was inversely correlated with the coverage of herbage species in June, July, and August in the sowing treatments. This inverse correlation indicates that competition between the herbage species and Z. japonica for light, nutrients, and water suppresses the growth of Z. japonica, and that the herbage species do not increase forage production before the establishment of Z. japonica. It appears that, in warm areas with few weeds, Z. japonica becomes established earlier when herbage species are not sown. 4. The effects of grazing and cutting on the establishment of Z. japonica were investigated and compared. In the first year, Z. japonica coverage did not differ significantly between the grazing and cutting plots. In the second year, the summer coverage was lower in the cutting plot because abundant Digitaria adscendens occurred in the plot. In the grazing plots, where plant heights were kept low by cattle grazing, Z. japonica dominated during the second year. In the grazing plots, the soil hardness and rate of solid phase of the soil were greater in the top layer, but the growth of tops and roots of Z. japonica, and root respiration, were not inhibited. Therefore, the establishment of Z. japonica was completed in 1 year under grazing conditions. 5. Changes in vegetation and soil properties in abandoned terrace paddy fields under grazing conditions after the transplanting of Z. japonica sod were investigated over the course of 3 years. When grazing started, bush species and Juncus effusus dominated. All plants were cut and open ditches were dug for drainage. In the top layer of the field, the rate of liquid-phase soil decreased, with the proportions of the solid and gas phases increasing : i.e., soil hardness increased rapidly. Plant coverage was low in the first year ; Z. japonica coverage began to increase in the second year and reached 45.8% in the third year. The Z. japonica biomass increased in the third year. The root weight of Z. japonica increased greatly in the second year, and roots grew to a depth of 10 cm. Thus, Z. japonica could be established in a couple of years in abandoned terrace paddy fields under ditch-drained or well-drained conditions in the presence of grazing. 6. The growth of grazed Z. japonica on the floor of a deciduous forest was investigated at three tree densities. The rooting ratios of Z. japonica sods were 75%, 86%, and 98%, respectively, at low (300 trees/ha), medium (440 trees/ha), and high (630 trees/ha) tree densities. The highest rooting rate (at high density) was ascribed to the suitable soil water content, which was maintained under the dense canopy. Coverage by Z. japonica at low density increased more rapidly than that at medium and high density in both the second and third years after transplanting. At low density, coverage of Z. japonica was 58% in October of the third year. The estimated leaf area index (ELAI) of the trees increased gradually from the first year to the third year in all treatments. The highest ELAI value was recorded at high density throughout the experiment. The values of relative solar radiation at the forest floor in the second year were 83% at low density. The amount of tree litter on the forest floor decreased from year to year in all treatments ; no appreciable differences were recognized among the treatments. The growth of Z. japonica was more rapid at low density (for trees averaging 9 m in height). 7. The effects of herbicide application (asulam, developed by Bayer Co.) and cutting on converting a bracken fern (Pteridium aquilinum L.) - dominated pasture into a Z. japonica - dominated pasture were investigated. The number of P. aquilinum shoots became 0.5/ m^2 two months after asulam treatment and increased slightly during the second year. However, in the cutting plot, in which vegetation was cut six times during the first year, the number of P. aquilinum shoots decreased year by year, and the fern had disappeared by the third year. This disappearance was probably caused by exhaustion of the rhizome nutrient reserves. The rooting rate of Z. japonica was lower in the cutting plots than in the asulam application plots because of competition with P. aquilinum. The coverage of Z. japonica in both plots increased in the second year, and reached 60% in the third year. Therefore, both asulam application and cutting were useful for converting pasture dominated by bracken fern into a Z. japonica pasture.},
 pages = {1--44},
 title = {遊休農林地の立地環境に適合したシバ草地造成法},
 volume = {8},
 year = {2009},
 yomi = {オオタニ, イチロウ}
}