• Korean Journal of Soil Science and Fertilizer
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• v.9 no.3
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• pp.165-181
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• 1976

Fertilizer(N,P,K) demand for crop production in 1980, 1990 and 2000 was estimated according to the two proposed models, one of which is fertilizer use efficiency model expressed in $Fn=(Y/E){\cdot}(1-Cs)Eu$, where Fn:fertilizer demand, Y:Crop production estimated, E:nutrient efficiency, Cs:fraction of natural resource nutrient in plant, Eu:fertilizer use efficiency and the other fertilization efficiency model expressed in Fn=Y(1-Cys)/Fe, where Cys:fraction of yield without fertilizer, Fe:fertilization efficiency. Total crop uptake of nutrient and its noncycling portion were estimated as criteria for fertilizer demand and nutrient maintenance. Total crop uptake of N,P,K was 600,000 M/T in 1965 700,000 M/T in 1974 and estimated to 880,000 M/T in 1980, 1,170,000 M/T in 1990 and 1,410,000 M/T in 2000. Fertilizer demand appeares to be about 90% of total crop uptake according to fertilizer use efficiency model and about 87% according to fertilization efficiency model. The noncycling nutrient was about 29% of total crop uptake. Fertilizer demand was almost same to the uptake amount in nitrogen, 1.5 times of uptake in phosphorus and half of uptake in potassium. Varietal development, improvement of soil fertility and cultivation method and development of fertilizer forms appears to decrease fertilizer demand by increasing efficiency term in two models while environmental stress such as low temperature appears to give reverse effect resulting in higher fertilizer demand. Fertilizer consumption in 1974 seemed to be unreasonably high especially in nitrogen and phosphorus and thus the effective use of fertilizer appeared as an urgent problem considering that large fields are still remained in lower fertility.

• Korea journal of population studies
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• v.16 no.2
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• pp.84-110
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• 1993

This study aims at identifying the recent change in marriage behaviors in Korea. The data used here is the vital statistics compiled from the vital registration system of which registration form is put on one from together with the civil registration form. According to the results of this analysis, since 1970 the number of marriages has steadily increased from about 300, 000 in the former of 1970s to about 400, 000 in the latter of 1980s, appproximately coincided with the change in population size at the marriageable age span. The few exceptions that can be seen in the 1970s seem to result from the impact of social upheavals during 1950s; since the birth cohorts affected by the low fertility during the Korean war and the post-war baby-boom generations chracterized by the high fertility entered the marriage market in the 1970s. However, the marriage rate shows a little increase from around 7 in the former of 1970s to around 9 in the latter of 1980s, indicating that the marriage prevalence has been more or less inconsiderably changed during this period. It is also found that the proportion of remarriage to the total marriages has increased to around 10 per cent in 1989, while decreasing that of first marriage. This fact can be attributable to the higher prevalence of divorces and the collapsing of the Confucianism ethic which contributed to expediting the remarriage of widows. Although this proportion is insignificant compared with that of the of more developed countries, it is not difficult to say that the proportion of remarriages will continue to increase in future. The age first at first marriage(AFM) which directly affects the span exposed to the risks pregnancy has increased to the age about 28 for male and about 25 for female in recent years. However, big difference in AFM between urban and rural areas has narrowed, resultant from the increasing involuntary postponement of marriage of rural young population who have met difficulties in seeking their bride or bridegroom in rural areas characterized by the heavy out-migration of young, particularly female, population. The present study shows the reverse relationship between AFM and educational attainment; i.e, the higher the educational attainment the lower the AFM. The conditions which are taken into considerations were the class and the family in the past time but which are, educational attainment, job and personal characteristics. With regard to the age condition, in recent years the male prefers the female younger than himself on the average by 3 years and vice versa, which is reduced form 4-5 years in beginning of 1970s. The age difference bride and bridegroom tends to decrease with the educational attainment increase. This may be attributable to the fact that the persons with the higher educational attainment prefer the love marriage and hence are more likely to choose their counterparts in the about same age. The education condition is characterized by the bridegroom having the higher educational level than bride. It is also significant to note that the proportion of love marriage has increased, whereas that of traditional arranged marriage has decreased. This is true in the urban areas than the rural areas, indicating that rights as well as responsibilities for marriage have been handed over the young population from their parents. In conclusion, the change in the marriage behaviors in Korea are characterized by increasing tendency for the postponement of first marriage, higher prevalences of divorces and a result remarriages, increase of love marriages, narrowing age difference between bride and bridegroom, etc. which are the main results of rapid industrization, increase in educational and economic activity opportunities and change in the ideals of marriages during the past decades. These phenomena prevailing in Korean society would affect not only the family structure that will become less proliferiated but the population size and structure. The most important is that the changes in marriage behaviors of Koreans and their impact on the society with respect to norms, values, morals, of individual and family in the social aspect, change in population size and structure in the demograpic aspects, and economic development in the economic aspects should be integrated into the plannings towards to the future.

• Korean Journal of Breeding Science
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• v.42 no.3
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• pp.307-312
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• 2010

'Cheonghaejinmi' is a new japonica rice variety developed from three-way cross between Samjiyeon/SR14694-57-4-2-1-3-2-2//Iri402 by the rice breeding team of National Institute of Crop Science, RDA. Heading date of this variety is August 18, 4 days later than that of 'Sobibyeo' in middle plain areas. It has culm length of 78 cm, 125 spikelets per panicle, 92.5% of ripened grain rate, and 23.9 g of 1000-brown rice weight. It showed 12 days of heading delay, and 63% spikelet fertility in cold-water irrigation stress. 'Cheonghaejinmi' is susceptible to blast disease, bacterial blight, virus diseases and plant hoppers. The nitrogen use efficiency of this variety is higher than that of Sobibyeo in low nitrogen application level. Milled rice of 'Cheonghaejinmi' exhibits translucent, clear non-glutinous endosperm and medium short grain. It has 5.9% protein content, 20.3% amylose content, and 0.28 palatability index of cooked rice compared to -0.11 of Hwaseongbyeo. The milled rice yield of 'Cheonghaejinmi' was about 5.31 MT/ha at low nitrogen application level of ordinary season culture. This variety had 98.8% whole grain in milled rice and 76% milling recovery of whole grain. 'Cheonghaejinmi' would be adaptable to middle plain areas and middle-western coastal areas in Korea.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.26 no.1
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• pp.1-31
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• 1981

Experiments were conducted to investigate rice varietal response to low water and air temperatures at different growth stages from 1975 to 1980 in a phytotron in Suweon and in a cold water nursery in Chooncheon. Germination ability, seedling growth, sterility of laspikelets, panicle exertion, discoloration of leaves, and delay of heading of recently developed indica/japonica cross(I/J), japonica, and indica varieties at low air temperature or cold water were compared to those at normal temperature or natural conditions. The results are summarized as follows: 1. Practically acceptable germination rate of 70% was obtained in 10 days after initiation of germination test at 15\circ_C for japonica varieties, but 15 days for IxJ varieties. Varietal differences in germination ability at suboptimal temperature was greatest at 16\circ_C for 6 days. 2. Cold injury of rice seedlings was most severe at the 3.0-and 3.5-leaf stage and it was reduced as growth stage advanced. A significant positive correlation was observed between cold injury at 3-leaf stage and 6-leaf stage. 3. At day/night temperatures of 15/10\circ_C seedlings of both japonica and I/J varieties were dead in 42 days. At 20/15\circ_C japonica varieties produced tillers actively, but tillering of I/J varieties was retarded a little. At 25/15\circ_C, both japonica and I/J varieties produced tillers most actively. Increase in plant height was proportional to the increase in all varieties. 4. In I/J varieties the number of differentiated panicle rachis branches and spikelets was reduced at a day-night temperature of 20-15\circ_C compared to 25-20 or 30-25\circ_C, but not in japonica varieties although panicle exertion was retarded at 20-15\circ_C. The number of spikelets was not correlated with the number of primary rachis branches, but positively correlated with that of secondary rachis branches. 5. Heading of rice varieties treated with 15\circ_C air temperature at meiotic stage was delayed compared to that at tillering stage by 1-3 days and heading was delayed as duration of low temperature treatment increased. 6. At cold water treatment of 17\circ_C from tillering to heading stage, heading of japonica, I/J, and cold tolerant indica varieties was delayed 2-6, 3-9, and 4-5 days, respectively, Growth stage sensitive to delay of heading delay at water treatment were tillering stage, meiotic stage, and booting tage in that order, delay of heading was greater in indica corssed japonica(Suweon 264), japonica(Suweon 235), and cold tolerant indica(Lengkwang) varieties in that order. Delay of heading due to cold water treatment was positively correlated with culm length reduction and spikelet sterility. 7. Elongation of culms and exertion of panicles of rice varieties treated with low air temperature 17\circ_C. Culm length reduction rate of tall varieties was lower than that of short statured varieties at low temperature. Panicle exertion was most severaly retarded with low temperature treatment at heading stage. Generally, retardation of panicle exertion of 1/1 varieties was more severe than that of japonica varieties at low temperature. There was a positive correlation between panicle exertion and culm length at low temperature. 8. The number of panicles was increased with cold water treatment at tillering stage, but reduced at meiotic stage. As time of cold water treatment was conducted at earlier growth stage, culm length was shorter and panicle exertion poorer. 9. Sterility of all rice varieties was negligible at 17\circ_C for three days but 30.3-85.2% of strility was observed for nine-day treatment at 17\circ_C. Among the tested varieties, sterility of Suweon 264 and Milyang 42 was highest and that of Suweon 290 and Suweon 287 was lowest. The most sensitive growth stage to low temperature induced sterility was from 15 to 5 days before heading. There was positive correlation between sterility of rice plants treated with low temperature at meiotic and heading stage. 10. Percentage of spikelet sterility was greatest at cold water treatment at meiotic stage (auricle distance -15～-10cm) and it was higher in 1/1 (Suweon 264, Joseng tongil), japonica (Nongbaek, Towada), and cold tolerance indica(Lengkwang) varieties in the order. Level of cold water and position of young-ear affected on the sterility of varieties at meiotic stage; percentage of spikelet sterility of variety, Lengkwang, of which young-ear was located above the cold water level was high, but that of short statured variety, Suweon 264, of which young-ear was located in the cold water was lower. 11. Percentage of ripened grains was not reducted at 15\circ_C air temperature for three days at full heading stage in all varieties. However, at six-day low temperature treatment Suweon 287, Suweon 264 showed percentage of ripended grains lower than 60%, but at nine-day low temperature treatment all varieties showed percentage of ripened grains lower than 60%. Low temperature treatment of 17\circ_C from 10 days after heading for 20 days did not affect on the ripening of all varieties. 12. Uptake of nitrogen, phosphorous, potassium, calcium, and magnesium in whole plants was higher at average air temperature of 25\circ_C, but concentration of the elements was lower compared to those at 19\circ_C. However, both total uptake and concentration of manganese were higher at 19\circ_C compared to 25\circ_C. 13. Higher application of nitrogen, phosphorus, silicate, and compost increased yield of rice due to increased number of panicles and spike let fertility in cold water irrigated paddy.

• Korean Journal of Soil Science and Fertilizer
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• v.7 no.1
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• pp.35-42
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• 1974

From the results of countrywide two year N. P. K simple trial with newly bred IR 667-Suwon 214 and leading local varieties for comparison soil productivity (yield without fertilizer) and fertilization productivity (yield increase with fertilizer) were investigated. 1. IR667 showed higher yield than leading local by 19% in 1971 and by 12% in the year of low temperature stress, 1972. High yielding capacity of IR667 was attributed to greater number of spikelet per panicle. The coefficient of variation in yield was smaller in IR667 but the leading locals showed higher yield in 23(1971) and 30% (1972) of the fields. 2. IR667 required more nitrogen, especially phosphorus and potassium. Fertilization efficiency (yield increment per unit fertilizer) in IR667 was-about 4kg higher in nitrogen but smaller in phosphorus and almost the same in potassium. 3. Soil productivity was higher in IR667 but percent contribution of soil productivity to total productivity (field productivity) was lower. 4. Percent contribution of fertilization productivity to field productivity was 19 to 33, of which 5 was due to phosphorus and potassium. 5. The greater the soil productivity, the greater the field productivity becomes, but the much greater the percentage contribution of soil productivity becomes. 6. Fertility saturation point at which fertilization efficiency is nil, was propoesd as a soil productivity (or field productivity) limit.

• The Korean Journal of Pesticide Science
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• v.2 no.3
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• pp.137-146
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• 1998

Laboratory tests were carried out to evaluate the effect of several insecticides with insect growth regulator (IGR) properties on the larval development of housefly, Musca domestica, which was collected at a large pigpen in Hamyang, Gyeongnam, Korea in 1997. Commercial formulations of the chemicals were diluted with tap water into a range of concentrations, and mixed with larval media. In addition to the IGRs, imidacloprid 5% WP was tested, too. The IGRs treated at the 2nd instar stage induced higher larval mortalities than percentages of malformed pupae. The result were, however, opposite when the IGRs were treated at the 3rd instar stage. Overall mortality resulting from larval death and malformed pupae was dependent on concentration. Diflubenzuron, teflubenzuron, triflumuron, flufenoxuron, tebufenozide, and imidacloprid, treated to the 2nd instar larvae, showed mortality over 95 % at concentrations of 5 ppm, 3 ppm, 30 ppm, 5 ppm, over 1000 ppm, 1000 ppm, respectively. Higher concentrations were needed to get the same level. of mortality in the 3rd instar larvae as that in the 2nd larvae. Overall mortality over 95% at the 3rd instar could be get at concentrations of 100 ppm, 10 ppm, 300 ppm, 10 ppm of diflubenzuron, teflubenzuron, triflumuron, flufenoxuron, respectively. Tebufenozide (1,000 ppm) and imidacloprid (300 ppm) were less effective than the other chemicals, showing only 36.7% and 86.7% mortalities, respectively. The chemicals also affected pupal weight at high concentrations. Decrease of pupal weight was distinct at high concentrations of teflubenzuron, flufenoxuron, tebufenozide, imidacloprid. Diflubenzuron and triflumuron were less effective. From these results it could be concluded that the IGR insecticides can be used as control agents by interfering with moulting and pupation process of housefly, by reducing pupal weight which could be resulted in low fertility and less oviposition.

• Korean Journal of Environment and Ecology
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• v.21 no.6
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• pp.544-553
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• 2007

This study is focused on the cultivation of seedlings and cuttings of roundleaf chastetree(Vitex rotundifolia L. f.) according to the sorts of soil and fertilization methods. The results are summarized as follows: When roundleaf chastetree seedlings(aged 1-0) and cuttings(aged 1-0) were cultivated in three different kinds of soil- sand, granite soil, and yellow silt- without any fertilization, 70% of the seedlings survived in sand and granite soil, and 35% did in yellow silt; 90% of the cuttings survived in granite soil and 80% did in sand and yellow silt. The general growth of both seedlings and cuttings was good in granite soil, and sand but relatively inferior in yellow silt. Seedlings showed good stem growth while cuttings had fine root growth. In case of cultivation of seedlings with different kinds and quantities of fertilizer adjusted and with granite soil as basic soil, seedlings and cuttings survived in the experimental section where only the organic fertilizer was used as basic fertilization; in contrast, seedlings grown in the experimental section were all dead where both inorganic and liquefied fertilizer were used. Cuttings showed considerably higher survival rates than seedlings at the experimental fertilization section; particularly, the survival rate of cuttings was twice as much as that of seedlings at the experimental section with low fertilization. This study results revealed that cuttings are desirable than seedlings in general rootage, growth, adaptability to soil, and cuttings have lower demand for soil fertility in time of growing roundleaf chastetree saplings.

• Journal of the Korean Geographical Society
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• v.47 no.3
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• pp.359-374
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• 2012

This paper intends to examine spatial patterns and regional variations of aging population in Korea based on census data for 163 areas during 1980~2010. It briefly investigates general characteristics of aging population in Korea from previous studies and clarifies spatial patterns of aging process at regional level with reference of population growth rate at different time periods. Cities in Korea are classified into several stages including aging society, aged society and super-aged society according to the percentages of aging population out of total population every five years. At the regional scale, the stage of aging society was revealed from 1980, while the stage of aged society was shown from 1995 and super-aged society was entered from 2000 in Korea. Eighty cities in the analysis were shown at the stage of super-aged society in 2010. The portions of aging population are highly related to city size and population growth rate. For instance, the cities both in small size and with low population growth rate are revealing high percentage of aging population. As of 2010, most rural areas are staged into super-aged society, while most cities within Seoul metropolitan area and mid-sized cities are kept in the stage of aging society. At regional scale, there are no significant statistical correlations between total fertility rate and aging population.

• The Korean Journal of Applied Statistics
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• v.28 no.4
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• pp.603-620
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• 2015

The National Pension of Korea is a public social security system designed to alleviate social risks and poverty that has had a major impact on the quality of life for the aging population. However, a rapidly aging population and low fertility threaten the sustainability of national pension in Korea. The National Pension Research Institute publishes a nancial projection every ve years; consequently, the government has lowered the entitlements for the sustainability of national pension based on the projection results. The current reform of the pension system that arbitrarily reduces the entitlements might detract from the income security role of the national pension for pensioners without accounting for the highest elderly poverty rate in the OECD countries. We first discuss methods for the financial projection of the national pension in terms of population, subscribers, and pensioner projections in order to estimate the pension reserve fund and the financial depletion year. We also conduct a sensitivity analysis for population variables, institutional variables, and economic variables based on pension reserves and the financial depletion year. We evaluate intergenerational fairness between the income hierarchy by conducting a money's worth analysis. Finally, we investigate the possibility of the sustainability of national pension by adjusting pension contributions and entitlements (income replacement rate). A new dependency ratio shows that a simple reform of the national pension does not secure the sustainability of the national pension without adapting a pay-as-you-go system.

• The Korean Journal of Applied Statistics
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• v.28 no.4
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• pp.643-661
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• 2015

Korea Teachers Pension (private school pension) is a mandatory pension and a social security system for private school teachers to ensure the stability of subscribers by a supplying pension when they (and their dependents) face future economic risk due to retirement or death. Therefore, the Teachers Pension must provide stability and sustainability in regards to adequacy of income and to function as a pension. However, the Government Employees Pension System (GEPS) of Korea (the most representative special occupation pension) recorded a fiscal deficit in 2001 and with an accumulated deficit that is expected to grow; subsequently, various plans for the reform of GEPS have been actively discussed. The Korea Teachers Pension system is based on the GEPS scheme and is not free from the GEPS discussions on reforms of national pension. The current system for the Teachers Pension needs to be improved because it is expected to be depleted within the next 30 years due to low fertility and an aging population in Korea. This study discusses existing Teachers Pension schemes problems and suggests a projection method and revised plans to improve it. We use long-term financial projections of the Teachers Pension to estimate the fund exhaustion point and the minus balance of the financial scale as well as analyze the supply-demand burden structure that reflects the future population structure to propose Teachers Pension reforms that will improve stability and adequacy.