• Korean Journal of Plant Resources
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• v.10 no.1
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• pp.100-104
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• 1997

A new baekji(Angelica dahurica Bentham et Hooker) variety, Baekji l, was developed through a pure line selection at the Gyeongbug Provincial RDA during the period of 1990 to 1995. The variety was characterized to have high plant height. Long root length and large root diameter as compared with a check varicty of Bonghwa baekji but emergence date, flowering date and leaf number of Baekji l was similar to that of the check variety, and it was also more tolerant to nematode and heat stress. Peeled root color of Backji l was yellowbrown but number of the lateral root of the variety was greater. The dried-root yield of Baekji l in yield trial, regional adaptation trial and farmer's field trial was always $21\sim31%$ higher than that of the check variety.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.54 no.4
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• pp.390-396
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• 2009

To select optimal shade material in paddy soil, growth characteristics and ginsenoside contents were investigated in new cultivar, 'Cheonpoong' of three-year-old ginseng cultured under three kinds of shade materials such as three-layered blue and one-layered black PE (polyethylene) net (TBPN), blue PE sheet (BPSS), and aluminium-coated PE sheet (APSS). The order of light transmission ratio and air temperature by shade materials were BPSS > APSS > TBSB among three shade materials. Average soil water tension in PDC and IDC was 64 mbar (absolute soil moisture, 25%) and 123 mbar (absolute soil moisture, 17%), respectively, and soil water tension in IDC was changed more distinctly than that of PDC by season and shade materials. Yield in PDC was distinctly decreased more than that in IDC because of the increase of discolored-leaf and rusted-root ratio. BPSS and TBPN among three shade materials were the most effective on the increase of yield in PDC and IDC, respectively. Ratio of rusty-colored root showed not significant difference by drainage class and shade materials. Contents of panaxatriol ginsenoside (Rg1, Re and Rf) were decreased in PDC, while it of panaxadiol ginsenoside (Rb1, Rc and Rd) were increased in IDC. Total ginsenoside contents of IDC was distinctly higher than that of PDC, and BPSS showed the highest contents among three shade materials regardless of poorly and imperfectly drainage class.

• Horticultural Science & Technology
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• v.29 no.4
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• pp.317-325
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• 2011

This study was conducted to examine the effect of supplemental lighting on the growth and yield of hydroponically grown sweet pepper (Capsicum annuum L. cv. sprit) under low levels of natural light in winter. The plants were treated with natural light only (control), 3-hour supplemental lighting before sunrise, after sunrise and after sunset with high pressure sodium (HPS, 400W). As the result of these three treatments, the supplemental lighting promoted photosynthesis in the low light intensity condition and particularly photosynthesis was more active right after sun rise in the morning, 1.5-$3.0{\mu}molCO_2{\cdot}m^{-2}{\cdot}s^{-1}$ comparing to those of supplemental lighting after sunset, 0.5-$1.5{\mu}molCO_2{\cdot}m^{-2}{\cdot}s^{-1}$. Transpiration rate and stomatal conductance sharply increased with supplemental lighting after sunrise then they decreased again after turning the lights off. Stomatal size was observed $32.2{\mu}m^2$ after supplemental lighting, whereas the size of the natural light was almost closed at $7.7{\mu}m^2$. The average plant height of sweet papper cv. spirit was 185 cm before sunrise, 188 cm after sunrise and 208 cm after sunset with supplemental lighting for 3hours while the control was 171 cm. With supplemental lighting a better number of fruit set per plant was measured 4.3 before and after sunrise, 3.7 after sunset but 2.6 in the control. Interestingly, there were no significant differences in the sugar content ($^{\circ}Brix$) degree between treatment of supplemental lighting, whereas slight differences between seasons were seen. The marketable fruit yield of sweet pepper (cv. spirit) was $116.0kg{\cdot}ha$ with supplemental lighting, whereas the control (natural light only) was $75.8kg{\cdot}ha$. Despite of spending electricity and depreciation cost, the economic analysis showed net income with supplemental lighting after sunrise was 51% higher than control treatment in cv. spirit.

• Journal of Animal Science and Technology
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• v.44 no.2
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• pp.251-260
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• 2002

The corn (Zea mays L) planting date in a double-cropping system is delayed until mid-May due to delayed rye harvest on May. This experiment was conducted to determine the optimum harvesting time for high yield and the best quality of silage corn at late planting date after harvesting winter rye. Corns were planted on 21 May and harvested at eight different maturity stage at Seoul National University Experimental Livestock Farm, Suwon in 1997. Maturities were B (blister; 16 days after silking), M (milk; 20 days), LM (late milk; 24 days), SD (soft dough; 28 days), ED (early dent; 33 days), FD (full dent; 38 days), LD (late dent; 44 days) and PM (physiological maturity; 53 days) stages. The percentage of whole plant dry matter (DM) showed optimum range for silage making (29.0 to 38.5%) when corn plant was harvested at between ED and LD stages. Maximum whole plant DM (14,831 kg/ha) and total digestible nutrients (TDN) yields (10,675 kg/ha) reached at full dent stage. The percentage of whole plant acid detergent fiber (ADF) was decreased from 35.4 to 22.1%, and that of neutral detergent fiber (NDF) was also decreased from 63.8 to 46.0% as harvest stage progressed. These changes in chemical compositions were associated with changes in plant part composition. A progressive increase in total ear, and the decrease in stover portion in the plant were observed with advance in harvest stage. Calculated on net energy for lactation (NEL) and TDN values based on ADF percentage of stover plant decreased by ED stage and then increased by PM stage. But NEL and TDN values of ear and whole plant increased as harvest stage progressed. While in vitro dry matter digestibility of stover was decreased from 61.1 to 49.7%, whole plant was increased from 58.3 to 65.7% as maturity advanced (P$<$0.05). The results of this study indicate that corn can be harvested for silage at full (1/2 milkline) and late dent (2/3 milkline) stages for maximum yield and optimum quality at late planting. And days after silking at late planting was 38 and 44 days.

• Journal of Animal Science and Technology
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• v.55 no.5
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• pp.343-349
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• 2013

Data including 1,372,050 milk records pertaining to 438,019 cows from 1983 to 2011 collected during performance tests conducted by the National Livestock Cooperative Dairy Improvement Center were used to calculate milk income and profit of individuals and investigate the effects of production levels of early lactation (parity 1 and 2, respectively). Individuals with a moderate level of early lactation stayed longer in herds. Among parity 1, the 9,000 kg or higher group had a lower mean number of lactations than the overall mean of 3.13. The 7,000 kg or lower and 10,000 kg or higher groups had lower mean life time milking days than the overall mean of 1,076.8 days. Standard deviations of lifetime traits tended to decrease as production levels increased. For parity 2, the 11,000 kg or higher group had a lower mean number of lactation than the overall mean of 3.43. The lifetime milking days was highest in the 12,000 kg group (1,212.0 days), and generally smaller in the lower groups. Profit increased as the production level of groups increased for both parity 1 and 2. In groups with low production levels, profit of parity 1 was higher than that of parity 2, while the reverse was true in groups with high production levels. These results suggest that individuals in the low production groups had a greater likelihood to be culled due to reproductive or other problems. Furthermore, the accuracy of the prediction of lifetime profit of individuals with a milk yield of 305 days seems to be higher for parity 2 than parity 1; therefore, it is desirable to predict lifetime profit using the 305d milk yield of parity 2. In conclusion, breeding goals are based on many factors in functions for the estimation of profit; however, production levels during early lactation (parity 1 and 2) can be used as indicators of profit to extend profitability.

• Journal of Bio-Environment Control
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• v.17 no.4
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• pp.288-292
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• 2008

This study was conducted to identify the effects of irrigation amount to produce high quality melon fruit in fertigation culture. Irrigation amount of during fruit harvesting period was doubled at the low irrigation point ($(-45{\sim}50\;kPa$) treatment as 115 mm as than that of the high irrigation point ($-20{\sim}25\;kPa$) treatment. The plant growth rates such as stem length, leaf weight and plant height were a little diminished at the low irrigation point ($-45{\sim}50\;kPa$) than those of the other treatments. Internode length was however not affected by irrigation amount. Fruit weight was lighter at the low irrigation point ($-45{\sim}50\;kPa$) than that of at the high irrigation point and fruit height was shorter, but fruit diameter was not affected by irrigation amount. Fruit soluble solid was $0.9^{\circ}Bx$ higher at the low irrigation point ($-45{\sim}50\;kPa$) than at the high irrigation point ($-20{\sim}25\;kPa$) and net index was higher. Total marketable yield was highest by 3,937 kg/10a at the high irrigation point ($-20{\sim}25\;kPa$), but the excellent marketable yield was highest by 2,531 kg/10a at the low irrigation point ($-45{\sim}50\;kPa$). Inorganic contents of the soil N, K, Ca and Mg were not affected by irrigation amount. It was therefore thought that optimum irrigation point to produce high quality melon fruit by fertigation culture was $-45{\sim}50\;kPa$ at ripening stage.

• Korean Journal of Soil Science and Fertilizer
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• v.42 no.1
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• pp.1-13
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• 2009

Understanding the net nutrient balance in a farming system is crucial in assessing the system's sustainability. We quantified N, P and K balances under vegetable organic farming in a Eutric Haplud and in West Java, Indonesia in five planting seasons from 2005 to 2007. The ten treatments and three replications, arranged in a completely randomized block design, included single or combined sources of organic fertilizers: barnyard manure, compos ts or green manures. The organic matter rates were adjusted every planting season depending on the previous crop responses. The result sshowed that the application of ${\geq}20$ t $ha^{-1}$ barnyard manure per crop resulted in positive balances of N, P, and K, except in the second crops of 2006 where potassium balance were -25 to -11 kg $ha^{-1}$ under the treatments involving cattle barnyard manure, because of low K content of these treatments and high K uptake by Chinese cabbage. Application of 20 to 25 t $ha^{-1}$ of plant residue or 5 t $ha^{-1}$ of Tithonia compost also resulted in a negative K balance. Soil available P increased significantly under ${\geq}25$ t $ha^{-1}$ barnyard manure and that under chicken manure had the highest available P. Accordingly, chicken barnyard manure gave the highest crop yield because of relatively higher N, P, and K contents. Plant residues gave the lowest yield due to the lowest nutrient content among all sources. Reducing the use of barnyard manure to 12.5 t $ha^{-1}$ and substituting it with Tithonia compost, Tithonia green manure or vegetable plant residue compost gave insignificantly different yield compared to the application of 25 t $ha^{-1}$ barnyard manure singly. In the long run, application of 25 t ha-1 cattle, goat, and horse manure or about 20 t $ha^{-1}$ chicken manure is recommendable for sustaining the fertility of this Andisol for vegetable production.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.25 no.1
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• pp.77-86
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• 1980

Asking to change the cropping patterns to save the labor and capitals in paddy rice cultivation, the study was intended to know the weed problems under the various possible cultural systems; namely, direct seeding (in broadcast and row), machine transplanting and hand transplanting. Under the conditions as weedy check plots, paddy yields were significantly variated among cropping systems, and the functions of panicle No. and spikelet No. to the yield were neglected, among others. However, the yield and yield components were narrowed among cropping systems, and the function of spikelets number per area was comparatively improved to the others.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.36 no.5
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• pp.407-428
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• 1991

The eastern coastal area having variability of climate is located within Taebaek mountain range and the east coast of Korea. It is therefore ease to cause the wind damages in paddy field during rice growing season. The wind damages to rice plant in this area were mainly caused by the Fohn wind (dry and hot wind) blowing over the Taebaek mountain range and the cold humid wind from the coast. The dry wind cause such as the white head, broken leaves, cut-leaves, dried leaves, shattering of grain, glume discolouration and lodging, On the other hand the cold humid wind derived from Ootsuku air mass in summer cause such symptom as the poor rice growth, degeneration of rachis brenches and poor ripening. To minimize the wind damages and utilize as a preparatory data for wind injury of rice in future, several experiments such as the selection of wind resistant variety to wind damage, determination of optimum transplanting date, improvement of fertilizer application methods, improvement of soils and effect of wind break net were carried out for 8 years from 1982 to 1989 in the eastern coastal area. The results obtained are summarized as follows. 1. According to available statisical data from Korean meteorological services (1954-1989) it is apperent that cold humid winds frequently cause damage to rice fields from August 10th to September 10th, it is therefore advisable to plan rice cultivation in such a way that the heading date should not be later than August 10th. 2. During the rice production season, two winds cause severe damage to the rice fields in eastern coastal area of Korea. One is the Fohn winds blowing over the Taebaek mountain range and the other is the cold humid wind form the coast. The frequency of occurrence of each wind was 25%. 3. To avoid damage caused by typhoon winds three different varieties of rice were planted at various areas. 4. In the eastern coastal area of Korea, the optimum ripening temperature for rice was about 22.2$^{\circ}C$ and the optimum heading date wad August 10th. The optimum transplanting time for the earily maturity variety was June 10th., medium maturity variety was May 20th and that of late maturity was May 10th by means of growing days degree (GDD) from transplanting date to heading date. 5.38% of this coastal area is sandy loamy soil while 28% is high humus soil. These soil types are very poor for rice cultivation. In this coastal area, the water table is high, the drainage is poor and the water temperature is low. The low water temperature makes it difficult for urea to dissolve, as a result rice growth was delayed, and the rice plant became sterile. But over application of urea resulted in blast disease in rice plants. It is therefore advise that Ammonium sulphate is used in this area instead of urea. 6. The low temperature of the soil inhibits activities of microorganism for phosphorus utilization so the rice plant could not easily absorb the phosphorus in the soil. Therefore phosphorus should be applied in splits from transplanting to panicle initiation rather than based application. 7. Wind damage was severe in the sandy loamy soil as compared to clay soils. With the application of silicate. compost and soil from mointain area. the sand loamy soil was improved for rice grain colour and ripening. 8. The use of wind break nets created a mocro-climate such as increased air. soil and water temperature as well as the reduction of wind velocity by 30%. This hastened rice growth, reduced white head and glume discolouration. improved rice quality and increased yield. 9. Two meter high wind break net was used around the rice experimental fields and the top of it. The material was polyethylene sheets. The optimum spacing was 0.5Cm x 0.5Cm. and that of setting up the wind break net was before panicle initiation. With this set up, the field was avoided off th cold humid wind and the Fohn. The yield in the treatment was 20% higher than the control. 10. After typhoon, paddy field was irrigated deeply and water was sprayed to reduce white head, glume discolouration, so rice yield was increased because of increasing ripening ratio and 1, 000 grain weight.

• Journal of the Korea Concrete Institute
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• v.24 no.6
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• pp.727-735
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• 2012

Recently, a high-strength strand of 2400 MPa was developed using domestic technologies. In 2011, KS D 7002 was revised to cover the newly developed high-strength strands to support their practical usage. Presently, however, discussions and evaluations are not sufficient on the mechanical properties of the strands and their performance in structural members. Also, there were no detailed reviews on the need to revise the current design code for practical use of the high-strength strands. In this study, flexural behavior of a member with the high-strength strands was estimated through sectional analysis and a review and comparison of the domestic and foreign design codes were conducted considering the analysis results. Also, the need for the revision of the design code was discussed. Such discussion especially focused on the estimation of the stress in strand, which related with various issues such as determination methods for yield point of strands, time-dependent loss of prestressing force, estimation of stress in strand at member failure, and net strain limit for ductile failure of member. The discussion revealed that some parts in the design code need a revision and the further studies are required.