• KOREAN JOURNAL OF CROP SCIENCE
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• v.39 no.4
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• pp.339-347
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• 1994

This experiment was conducted to investigate duck-raising system and the optimum nitrogen fertilization level in duck-raising field. Optimum duck rasing density in rice paddy field was 1, 000~1, 500 heads per ha and ducks could be harvested three times in a year starting from 40 days after mature-seedling machine transplanting. When 1, 000~1, 500 heads per ha of ducks was raised once a year, optimum nitrogen application level was 110kg/ha. In the case of three times in a year, it was 8.8kg/ha. The weed control rate of the duck-raised paddy field was superior(93~96%) to control (89%, treated twice with herbicide).

• Korean Journal of Organic Agriculture
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• v.22 no.2
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• pp.347-357
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• 2014

This study was conducted to evaluate the control effect of sodium dichloroisocyanurate (NaDCC) for Venturia nashicola on Niitaka pear during flowering period. As a nontoxic disinfectant, sodium dichloroisocyanurate is widely used in the field of hygiene and disease prevention, medical treatment, aquiculture as well as plant protection. NaDCC was sprayed on the pear tree inoculated with conidia ($4.5{\times}10^5spores/mL$) of Venturia nashicola and as a result the incidence of pear scab was 23.8% in 750mg/L and 26.2% in 1,000mg/L compare to the 51.6% incidence in untreated tree. No damage in the pollen of pear flower was detected with NaDCC treatments in the full bloom period for six pear cultivar including Wonwhang. A NaDCC single treatment in the early bloom of Niitaka pear showed more than 98% of fertilization rate. Furthermore, there was no incidence of Venturia nashicola on Nitaka pear trees treated with NaDCC 4 times during their growth period.

• Journal of Fisheries and Marine Sciences Education
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• v.26 no.6
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• pp.1402-1411
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• 2014

This study about morphological observation of pre- or post ovulated eggs obtained from artificially maturated female eels. Female eels were divided with two groups as wild eels from nature and feminized eels from farm. Artificial maturation had been conducted with the established methods in this laboratory, and then maturate eggs sampled at fixed 3 times and these were observed with stereomicroscope. Rate of increased body weight (RIW) were measured with 2 times. Egg diameters and development of oil droplets are determined for standardization of egg maturation degree, and the transparency of egg cytoplasm and the homogeneous degrees of egg size were referred to determine of egg quality. Rate of increased body weight (RIW) were good in range about 10 % at final salmon pituitary extracts (SPE) injection time and in range about 20 % at $17{\alpha}$, $20{\beta}$-dihydroxy-4-pregnen-3-one (DHP) injection time. Good matured egg for fertilization had $900-1000{\mu}m$ diameter, and they had about 50 oil droplets in size about $100{\mu}m$ diameter. There were not predominant differences at egg size and oil droplet development between wild female and feminized eels.

• Korean Journal of Soil Science and Fertilizer
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• v.8 no.4
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• pp.199-217
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• 1975

For the establishment of efficient method of potassium topdressing on rice the optimum time and amount were investigated and discussed on the basis of available data from nutriophysiological studies, soil characteristics and fertilizer trials in fields. The followings were pointed out. 1. According to yield rice plants require more potassium around heading under water culture. 2. Potassium involves in harvest index, filled grain ratio, grain weight and number of spikelets per panicle. 3. Potassium is lost after heading in most fields in spite of highest requirement during this period. 4. The higher $K_2O/N$ ratio in straw at harvest is, the higher the yield. 5. Relatively low efficiency of potassium fertilizer under the field condition may be due to improper application method rather than natural supply from soil and irrigation water. 6. Appropriate topdressing time appears at in effective tillering stage for the prevention of nitrogen excess and at 15 to 20 days after transplanting, ear formation stage and 5 days after heading for the prevention of soil reduction damage. Two times of topdressing for clayey soil and three times for sandy soil seems reasonable in practice together with nitrogen topdressing, 7. The reasonable ratio basal to topdressing of potassium fertlizer seems to be 2/3 and $N/K_2O$ ratio of fertilization for ear formation stage appeared also as 2/3.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.40 no.1
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• pp.9-15
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• 1995

This study was carried out to investigate the effects of the optimal fertilizer application levels and planting space at different seeding parts on Chinese yam from 1992 to 1993. The results obtained was as follows： The earlist day to emergence was 42~56 days at tuber section, 37~46 days at an aerial tuber, and 50~56 days at an exposed parent material. in turn. The days to emergence were delayed by increasing fertilizer application levels. In the growth of the under-ground parts, vine length was increased in a tuber section, aerial tuber, and an exposed parent material in turn. The tuber section by 60${\times}$20cm at planting space, 56-56-64 Kg/10a at fertilizer application levels was appeared to be good growth among underground parts. As planted close, the growth of tuber section was decreased. The totoal yield was appeared to be increased about 19% in a tuber section planted as 30${\times}$20cm compared with 60${\times}$20cm. In an exposed parent ma-terial, the planting space, 30${\times}$15cm, was increased 10% compared with 45${\times}$15cm, and in an aerial tuber, the planting space, 10${\times}$10cm, was increased about 10% comparing 30${\times}$10cm. Fertilization level(N-$P_2O_2K_2O$) in 56-56-64Kg/10a was increased 39 to 47% comparing 28-28-32 Kg/10a. And the heavy dressing and the close planting space were appeared to be produced the highest yield. In considering commercial quality, the optimal combination between seeding parts and planting space is recommended to improve commercial qualities and high yield.

• Journal of Life Science
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• v.23 no.9
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• pp.1079-1087
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• 2013

Speed germination success and robust vegetative growth of citrus rootstock through improved sowing methods and fertilizer inputs offer the usage of root system for the citrus. The current study evaluated the influence of seed coat removal and different fertilizer concentrations on plant germination and plant growth of spontaneous rootstock siblings. Decoated and coated seeds of diploid and tetraploid plants were sown in tubes. Commercial fertilizer concentrations of 0, 2, 4, 6, 8 and $10g{\cdot}l^{-1}$ were added. The experimental layout followed a randomized block $2{\times}6$ factorial design (seed coat removal ${\times}$ fertilizer concentration) for each rootstock. Fertilizer concentrations were 0, 10, 20 and $30g{\cdot}l^{-1}$ of the fertilizer for the resistance of the strength on the salt level. The germination rate of seeds without testa sown in vitro was improved (67-80%) compared to that of nontreated seeds. The eventual tree height of the seeds without testa in the diploid group was increased due to higher fertilization compared to that in the nontreated group. The removal of seed testa promoted the seed germination of both diploid and tetraploid trifoliate orange and resulted in greater height. Their vegetative development was also increased due to the increased fertilization of the rootstock. The Fv/Fm value for the diploid plants was 0.4 and 0.8 for the tetraploid ones under salt stress after 11 days of treatment. The removal of seed testa may improve the seed germination of trifoliate orange. Tetraploid trifoliate orange appears to possess resistance to salt stress compared to the diploid variety.

• Korean Journal of Soil Science and Fertilizer
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• v.25 no.3
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• pp.275-280
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• 1992

Inoculation responses of alfalfa[Medicago sativa(L.) Vernal] to Rhizobium meliloti with nitrogen fertilization were characterized by soil populations and plant yields from 1989 to 1991 at cultivated upland soil, which contained $3.1{\times}10$cells of R. meliloti/g.soil. The results obtained accordingly to fertilizing with 8Kg N/10a and differently inoculating the host such as initial and annual inoculation methods were as follows : 1. Soil populations of R. meliloti were increased more at no nitrogen fertilized condition compared to nitrogen fertilized condition to 2nd year experiment from 1st year that came up $1.6{\times}10^3$cells/g.soil, but at 3rd year the trend was reversed. Between inoculation methods, on the whole, the annual inoculation caused more populations, which were $2.0{\times}10^4$cells/g.soil in maximum number. And the populations declined after winter but recovered passing through summer season. 2. Alfalfa yields were mainly influenced by rhizobial populations rather than by fertilizing nitrogen showing a significant correlation(Y=0.36+0.287X, $r^2=0.58^{**}$) with the former. The increased extents of yields obtained by inoculation at no nitrogen and nitrogen fertilized conditions, respectively, were 66 and 10% in 1st : 13 and 20% in 2nd : 19 and 13% in 3rd year experiment with the initial inoculation, and were 66 and 10% in 1st ; 30 and 20% in 2nd : 35 and 36% in 3rd year experiment with the annual inoculation. 3. The results demonstrated the importance of inoculating, if possible, annual inoculating alfalfa to get much yields even at cultivated upland soil.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.3 no.3
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• pp.177-186
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• 1970

The spawning of the abalone, Haliotis discus hannai, was induced In October 1969 by air ex-position for about 30 minutes. At temperatures of from 14.0 to $18.8^{\circ}C$, the youngest trochophore stage was reached within 22 hours after the egg was laid. The trochophore was transformed into the veliger stage within 34 hours after fertilization. For $7\~9$ days after oviposition the veliger floated in sea water and then settled to the bottom. The peristomal shell was secreted along the outer lip of the aperture of the larval shell, and the first respiratory pore appears at about 110 days after fertilization. The shell attained a length of 0.40 mm in 15 days, 1.39 mm in 49 days, 2.14 mm in 110 days, 5.20 mm in 170 days and 10.00 mm in 228 days respectively. Monthly growth rate of the shell length is expressed by the following equation :$L=0.9981\;e^{0.18659M}$ where L is shell length and M is time in month. The density of floating larvae in the culture tank was about 10 larvae per 100 co. The number of larvae attached to a polyethylene collector ($30\times20\;cm$) ranged from 10 to 600. Mortality of the settled larvae on the polyethylene collector was about $87.0\%$ during 170 days following settlement. The culture of Nauicula sp. was made with rough polyethylene collectors hung at three different depths, namely 5 cm, 45 cm and 85 cm. At each depth the highest cell concentration appeared after $15\~17$ days, and the numbers of cells are shown as follows: $$5\;cm\;34.3\times10^4\;Cells/cm^2$$ $$45\;cm\;27.2\times10^4\;Cells/cm^2$$ $$85\;cm\;26.3\times10^4\;Cells/cm^2$$ At temperatures of from 13.0 to $14.3^{\circ}C$, the distance travelled by the larvae (3.0 mm In shell length) averaged 11.36 mm for a Period of 30 days. Their locomation was relatively active between 6 p.m. and 9 p.m., and $52.2\%$ of them moved during this period. When the larvae (2.0 mm in shell length) were kept in water at $0\;to\;\~1.8^{\circ}C$, they moved 1.15cm between 4 p.m. and 8 p.m. and 0.10 cm between midnight and 8 a.m. The relationships between shell length and body weight of the abalone sampled from three different localities are shown as follows: Dolsan-do $W=0.2479\;L^{2.5721}$ Huksan-do $W=0.1001\;L^{3.1021}$ Pohang $W=0.9632\;L^{2.0611}$

• Current Research on Agriculture and Life Sciences
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• v.1
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• pp.19-26
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• 1983

To investigate the influences of morphological features and the chemical compound of rice grain on the crack of rice kernels, rice was cultivated under the different method of fertilizer application and was harvested at optimal and late stage to the crack features of kernels of cracked and healthy grains. The results are summarized as follows ; The occurrence of cracked kernel was more severe in "Samgang-byeo" than in "Nagdong-byeo" and the rice harvested at the late stage was more cracked kernel than that of optimal harvest. The application of silicate fertilizer in addition to the N.P.K. fertilizer resulted in the decrease of cracked kernels. The grain weight, the grain volume (length ${\times}$ width ${\times}$ thickness), grain length and grain length/grain width etc. of the cracked kernels were larger than those of the healthy grains. The long "Samgang-byeo", having the long grain Shape, which has larger ratio of grain length/grain width than that of "Nagdong-byeo", shows higher rate of cracked kernels. The grain of "Samgang-byeo" which is easily cracked relatively it contains lower silica and higher phosphorus while "Nagdong-byeo" shows the opposite results. The ratio of silica/phosphorus in the grain was low in "Samgang-byeo" but it was high in "Nagdong-byeo". The ratio of silica/phosphorus in rice grain was increased by the application of silicate fertilizer in addition with N.P.K. fertilizers.

• Korean Journal of Ichthyology
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• v.27 no.2
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• pp.63-70
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• 2015

This research is about spawning behavior and morphological development of the eggs and larvae of fringed blenny which lives in Korean sea. It helps to find out the relation between fringed blenny larvae and other stichaeidae larva. Moreover, it is going to use for the basic data of taxonomical research. There were 8 mother fishes (total length 31.8~34.0 cm, average $32.9{\pm}0.21cm$), which were captured from the cost of Sindeok-dong, Yeosu-si, Jeollanam-do from December, 2010. we used trap to capture them. Mother fishes were brought to glass aquarium ($50{\times}30{\times}35cm$) and nurtured with recirculate rearing system. Breeding water temperature was $12.3{\sim}15.8^{\circ}C$ (average $14.1{\pm}2.47$) and salinity was 32.5~33.5‰ (average $33.0{\pm}0.05$‰). fertilized egg was round, opaque demersal egg. The size was 1.81~2.19 mm (average $2.00{\pm}0.27mm$, n=50). Incubation was begun after 271 hours and 30 minutes from fertilization. It started with piercing the egg membrane. prelarvae had length of 8.45~8.84 mm (average $8.65{\pm}0.28mm$, n=5) right after the incubation, and both mouth and anus were opened. After 11 days from the incubation, postlarvae had length of 10.5~11.3 mm (average $10.9{\pm}0.57mm$), and the number of myotomes was increased to 66.