• Journal of The Korean Society of Grassland and Forage Science
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• v.7 no.2
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• pp.71-78
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• 1987

This experiment was carried out to examine the effects of sowing method and summer management on the dry matter yield, dead matter, weed development and ground cover of orchardgrass (Dactylis glomerata L.) meadow. The experiment was allocated as a split-split plot design with three replications. The main plots were sowing method of drilling and broadcasting, sub plots were drainage of experimental field, adequate and inadequate, and sub-sub plots were cutting timeof orchardgrass, cutting before rainy season started and cutting after rainy season ended. The experiment was undertaken over a period of 14 months from September, 1983 to October, 1984. The results obtained are summarized as follows: 1. There were no significant differences in dry matter yield among treatments at the first cutting, but cutting before rainy season produced significantly more forage yield ($P{\le}0.01$) than cutting after rainy season at the second and third cuts. At the third cutting, drilled orchardgrass meadow showed a significant dry matter yield ($P{\le}0.05$) than broadcast orchardgrass meadow, 2. The dead matter of orchardgrass was accumulated only at the second cutting when orchardgrass meadow cut after rainy season. Orchardgrass produced in the adequate and inadequate drainage plots consisted 20.4 and 35.9% of dead material, respectively, but no significant difference was found between two drainage treatments. 3. Drilled orchardgrass meadow produced significantly less weeds ($P{\le}0.05$) than broadcast orchardgrass meadow, but the plots cut after rainy season produced significantly more weeds ($P{\le}0.01$) than the plots cut before rainy season. 4. The percent ground cover of orchardgrass in the plots cut before rainy season was significantly higher ($P{\le}0.01$) than that in the plots cut after rainy season at the second cutting. Drilled plots showed a slight increase in the ground cover than the broadcast, but the difference was not significant. The same trend of ground cover of the meadow estimated at the second cutting was sustained after the third cutting. 5. Based on the results of the experiment, it indicates that the second cut of orchardgrass should be made before rainy season related for maintaining high yield of the meadow. Drilling as a sowing method of orchardgrass meadow could be adopted in the view point of reducing weed development.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.4 no.1
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• pp.71-79
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• 1999

As part of an on-going project investigating flux of materials in the Keum River Estuary, we have monitored seasonal variations of nutrients, suspended particulate matter (SPM), chlorophyll, and salinity since 1997. Meteorological data and freshwater discharge from the Keum River Dike were also used, Our goal was to answers for (1) what is the main factor for the seasonal fluctuation of nutrients in the Keum River Estuary? and (2) are there any differences in nutrient distributions before and after the Keum River Dike construction? Nitrate concentrations in the Keum River water were kept constant through the year. Whereas other nutrients varied with evident seasonality: high phosphate and ammonium concentrations during the dry season and enhanced silicate contents during the rainy season. SPM was found similar trend with silicate. During the rainy season, the freshwater discharged from the Keum River Dike seemed to dilute the phosphate and ammonium, but to elevate SPM concentration in the Keum Estuary. In addition, the corresponding variations of SPM contents in the estuarine water affected the seasonal fluctuations of nutrients in the Estuary. The most important source of the nutrients in the estuarine water is the fluvial water. Therefore, the distribution patterns of nutrients in the Estuary are conservative against salinity. Nitrate, nitrite and silicate are conservative through the year. The distribution of phosphate and ammonium on the other hand, display two distinct seasonal patterns: conservative behavior during the dry season and some additive processes during the rainy days. Mass destruction of freshwater phytoplankton in the riverine water is believed to be a major additive source of phosphate in the upper Estuary. Desorption processes of phosphate and ammonium from SPM and organic matter probably contribute extra source of addition. Benthic flux of phosphate and ammonium from the sediment into overlying estuarine water can not be excluded as another source. After the Keum River Dike construction, the concentrations of SPM decreased markedly and their role in controlling of nutrient concentrations in the Estuary has probably diminished. We found low salinity (5~15 psu) within 1 km away from the Dike during the dry season. Therefore we conclude that the only limited area of inner estuary function as a real estuary and the rest part rather be like a bay during the dry season. However, during the rainy season, the entire estuary as the mixing place of freshwater and seawater. Compared to the environmental conditions of the Estuary before the Dike construction, tidal current velocity and turbidity are decreased, but nutrient concentrations and chance of massive algal bloom such as red tide outbreak markedly increased.

• Proceedings of the Korea Water Resources Association Conference
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• 2005.09b
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• pp.1178-1178
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• 2005

• Asian Journal of Turfgrass Science
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• v.15 no.2
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• pp.51-64
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• 2001

Summer stress is one of the serious problems on cool-season grass at the soccer fields in Korea during heavy rainy season. This study was conducted to intestigate the effect of shade net with regard to its percent (0, 50, 75), color (black, green), height (0 cm, 30 cm) and time (7 hr, 24 hr) on turf canopy temperature, light intensity, leaf color, turf performance, clipping yield and root dry weight of cool-season turfgrass. Turf canopy temperature was 6~13$^{\circ}C$ under black and green shade net when temperature was over 4$0^{\circ}C$. Light intensity was also decreased from 40 to 94% under black and green shade net compared to control. Black shade net was more effective than green net in reduction of temperature and light intensity. Green shade net was found to be better for photosynthesis of cool-season grass. Leaf color, turf performance, clipping yield, and root dry weight were better and increased under 50% and 75% shade net. 50% black shade net with 30cm height and 7 hr treatment showed the best turf performance. It can be concluded that 50% and 75% green shade net can be used fur reducing summer stress on cool-season grass after soccer marches during heavy rain season. The shade net decreased the turf canopy temperature and reduced heating damage of cool-season turfgrass.

• Horticultural Science & Technology
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• v.34 no.3
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• pp.383-395
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• 2016

This study investigated the effect of exogenous hydrogen peroxide ($H_2O_2$) on the antioxidant responses and growth of warm-season turfgrass (Zoysia japonica Steud.) and cool-season turfgrass (Poa pratensis L.) subjected to drought stress. Compared with control plants that were not pretreated with $H_2O_2$, plants pretreated with $H_2O_2$ had significantly greater fresh and dry weights of shoots and roots, and increased water content. $H_2O_2$ pretreatments before drought stress significantly decreased the concentrations of malondialdehyde and $H_2O_2$. DPPH radical scavenging and glutathione activities were significantly increased. The responsive activities of the antioxidant enzymes superoxide dismutase, ascorbate peroxidase, catalase, and peroxidase were also significantly enhanced. Our results suggest that exogenous $H_2O_2$ could improve the growth of warm-season and cool-season turfgrass under drought stress by increasing the activity of their antioxidant enzymes, while decreasing lipid peroxidation.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.3
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• pp.262-272
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• 2005

This study was undertaken to obtain design concentrations for the natural system treating stream water flowing into estuarine lake(Sapgyo). This lake has three major, so called, national-class streams: one is Gokgyo flowing through two medium-size municipal areas and the others are Muhan and Sapgyo placed in mostly rural area nested with some small towns. The results of three year's investigation showed big changes in water quality during the period between dry and wet seasons. Nitrogen concentration usually decreases as the flow rate increases. The change of phosphorus concentration in Gokgyo was the same pattern as nitrogen, but in other two streams it was inversely related with flow rates. This is probably due to the chemical property of the particles washed out from the different stream basins during wet season. It was found that about 40 to 60% of the total nitrogen are in soluble form and on average, 35% of the total phosphorus consists of dissolved-P. Representative concentration of these streams has to be separately determined based on dry and wet season. TDS and SS could be indicating parameters useful to depict and characterize a change of water quality with respect to flow rate because their measurement is easy and also includes a small analytical error. TDS values measured during dry season are related with high nitrogen concentration while during wet season, SS values effectively reflect a high concentration of phosphorus. For design purpose, cumulative concentration distribution graph presented in this paper can be directly or indirectly applied to other streams through a brief comparative and verificative study.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.31 no.6
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• pp.450-457
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• 2019

Sedimentation is a common problem for river ports. But its intensity depends on the rate of sedimentation, channel shape and size, hydrodynamic behavior of the river and the importance of the port. High sedimentation rate in Yangon River has become one major issue for Myanmar as her largest port is located on the Yangon riverbank. As a result of the high sedimentation rate, shallow water area near the confluence of Yangon River, Pazundaung Creek, and Bago River keeps blocking the navigation channel to the Yangon Port, which also limits the size of vessel calling to Yangon Port. Therefore, studies to understand sediment transport process in Yangon River are required because the economic development of Myanmar highly relies on the Yangon Port. This paper aims to calculate the sediment transport and to predict the riverbed elevation changes in Yangon River by using Bagnold (1966) theory. Calculation result shows that huge difference can be found in the bed load transport between the rainy season and dry season in Yangon River, and thus the sedimentation problem would become more severe in the dry season when the transported sediments are reduced. The estimated sedimentation rate in dry season indicates that the rate of riverbed level rise near the Yangon Port area is about 0.063 m per year, which would lead to approximately 3.15 m rise in the riverbed level in next 50 yrs, considering the same workload of dredging to maintain the navigation channel.

• Proceedings of the Korean Society of Near Infrared Spectroscopy Conference
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• 2001.06a
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• pp.1611-1611
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• 2001

The main selection parameters used by forage grass (rye and Italian rye grass) breeders are dry-matter yield, seasonal growth, persistency, disease resistance, heading date, and heading. These characteristics can all be identified usually in the segregating F2 population, however characteristics such as soluble carbohydrate level, protein, lipid and digestibility cannot be identified. The emphasis of this work is to introduce a quantitative selection process for characterization of herbage quality e.g. protein, water-soluble carbohydrates, fiber fractions, dry matter digestibility. NIRS calibrations are currently being developed for identifying grass genotypes to assist the selection process, thereby allowing the opportunity to actively breed improved herbage quality. The changes in fibre fractions, associated components and digestibility of a number of grass clones at different growth stages are being assessed changes taking place during a growing season. This will provide a database of the major changes taking place during a growing season. Attempts to classify quality differences between genotypes will be carried out using multivariate analysis of the spectral data. I addition changes associated with maturity of grass will be considered in order to develop robust calibrations.

• Asian Journal of Turfgrass Science
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• v.5 no.1
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• pp.23-32
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• 1991

The purpose of this study was to determine the vegetative growth of two cool season turfgrasses during summer season in Korea. Ten respective cultivars of Kentucky bluegrass [Poapratensis L.] and perennial ryegrass [Lolium perenne L.] were exposed to unshaded, 30% and 60% shade for 4odays. First mowing height was 7cm, and then clippings were harvested every ten days at the same height. Shading increased the total length of clippings of all cultivars of two turfgrasses, but fresh and dry weight were significantly decreased. The highest shoot length obtained at 30% shade in Kentucky bluegrass and at 60% shade in perennial ryegrass. 'Rugky', 'Sydsport', 'Wabash' and 'Baron' of Kentucky bluegrass and 'Repel', 'Omega II', 'Ovation', 'Linn', 'Bell' and 'Manhattan' of perennial ryegrass showed relatively high tolerance to shade. Especially, in 'Citation II' perennial ryegrass, fresh and dry weight were increased by 30% shade. The number of tillers generally decreased with increasing shade. In 30% shade, 'Midnight' Kentucky bluegrass and 'Omega II' perennial ryegrass were least reduced and 'Baron' Kentucky bluegrass and 'Pennant' perennial ryegrass were most reduced. The cultivars of lower growth habit in full sunlight showed shade tolerance compared to those of higher growth habit.

• Asian-Australasian Journal of Animal Sciences
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• v.18 no.3
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• pp.345-349
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• 2005

A study was conducted to determine the effect of feeding chopped whole sugar cane compared to corn silage on performances of dairy cows during the dry season. Twenty four Holstein Friesian crossbred (>87.5% Holstein Friesian) lactating dairy cows in mid lactation; averaging 16.5${\pm}$2.0 kg of milk, 121${\pm}$22 days in milk, 54.5${\pm}$4.5 months old and 440${\pm}$31 kg live weight, were stratified for milk yield, days in milk, age, stage of lactation and body weight, and then randomly allocated to two treatment groups (12 cows in each group). The first group was fed corn silage together with commercial concentrate while the second group was fed chopped whole sugar cane together with commercial concentrate. All cows consumed similar DM, however, cows on corn silage consumed more CP while cows on chopped whole sugar cane consumed more $NE_{LP}$. No significant differences in performances between the two groups were observed except for final live weight and body weight change. Cows on chopped whole sugar cane showed higher final live weight and gained more weight than cows on corn silage. The present study clearly indicates that chopped whole sugar cane can be fed to lactating dairy cows, while giving similar milk yield to corn silage.