• Title/Summary/Keyword: direct-seeded

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Control of Sound Pressure inside a Flow Excited Cavity by Regulation of Vorticity Shedding (와류진동 조절에 의한 유동가진 공동 내부의 음압 제어)

  • Park, Jong-Beom;Hwang, Cheol-Ho
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.17 no.12
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    • pp.1223-1229
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    • 2007
  • Flow traveling over a cavity opening forms a vortex due to unstable shear layer and induces an aerodynamic pressure excitation from the diffusion of the vortex convecting out of the trailing edge of the opening. The interaction between the excitation force and the cavity response sustains resonance in the resonator(cavity) and locked-in vortex shedding at the leading edge of the opening. The aerodynamic excitation force can be described from the diffusion of the vortex over the trailing edge and the level of its diffusivity is related to the strength of vorticity seeded at the leading edge. In this study, the control scheme of the internal pressure oscillation was proposed from regulating the vorticity at the leading edge by use of an oscillating spoiler. It was found that the relative motion between the spoiler and the air mass at the cavity opening influenced vorticity strength and the control was achieved by direct feedback of the cavity pressure fluctuation to the actuator.

Control of Sound Pressure Inside a Flow Excited Resonator (유동가진 공명기 내부의 음압 제어)

  • Hwang, Cheol-Ho;Park, Jong-Beom
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2005.11a
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    • pp.196-199
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    • 2005
  • Flow traveling over a cavity opening forms a vortex due to unstable shear layer and induces an aerodynamic pressure excitation from the diffusion of the vortex convecting out of the trailing edge of the opening. The interaction between the excitation force and the cavity response sustains resonance in the resonator(cavity) and locked-in vortex shedding at the leading edge of the opening. The aerodynamic excitation force can be described from the diffusion of the vortex over the trailing edge and the level of its diffusivity is related to the strength of vorticity seeded at the loading edge. In this study, the control scheme of the internal pressure oscillation was proposed from regulating the vorticity at the leading edge by use of an oscillating spoiler. It was found that the relative motion between the spoiler and the air mass at the cavity opening influenced vorticity strength and the control was achieved by direct feedback of the cavity pressure fluctuation to the actuator.

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Effect of Seeding Methods and Nitrogen Fertilizer Rates on the Forage Quality and Productivity of Whole Crop Rice (파종방법 및 질소시비량이 총체 벼의 수량 및 사료가치에 미치는 영향)

  • Kim, Jong Geun;Park, Hyung Soo;Lee, Sang Hoon;Jung, Jeong Sung;Ko, Han Jong
    • Journal of The Korean Society of Grassland and Forage Science
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    • v.35 no.2
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    • pp.87-92
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    • 2015
  • This experiment was conducted to evaluate the effect of seeding methods and application levels of nitrogen fertilizer on the yield and forage quality of whole crop rice (WCR). The WCR variety "Namil" was directly seeded on April 25 and transplanted on May 25. Five levels of nitrogen fertilizer were applied (90, 110, 140, 170 and 200 kg/ha). There were no significant differences (p<0.05) of the emergence date, heading date and disease resistance based on the nitrogen fertilizer rates; however, the WCR became dark at higher nitrogen fertilizer rates. The plant height increased at higher nitrogen fertilizer rates and the tiller number showed the same trend. In contrast to a direct seeding method, transplanting increased the tiller number. The dry matter (DM) content did not show a certain tendency based on nitrogen fertilizer rates, while the fresh and dry matter yields increased with incremental changes of the nitrogen fertilizer rates (p<0.01), and the transplant method increased the yield size. In yield analysis, the plot direct-seeded with 140 kg N/ha and the transplanting with 170kg N/ha showed the highest yields. The crude protein (CP) content increased with higher nitrogen fertilizer rate, but there was no significant differences between transplant and direct-seeding methods. The content of ADF (acid detergent fiber) and NDF (neutral detergent fiber) increased with higher nitrogen fertilizer rate, but total digestible nutrient (TDN) content decreased with increased nitrogen levels. Although high nitrogen applications increased the fresh and DM yields, the 140 kg/ha nitrogen fertilizer level is recommended as the proper nitrogen fertilizer level, considering both yield and the environments.

Reasonable Seeding Rate for Ridge Direct Seeding on Dry Paddy of Rice as an Irrigation Water-Saving Cultural System (벼 휴립건답직파 절수재배에 알맞은 파종량)

  • Choi Weon-Young;Park Hong-Kyu;Kim Sang-Su;Shin Hyun-Tak;Choi Sun-Young
    • Korean Journal of Agricultural and Forest Meteorology
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    • v.2 no.4
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    • pp.143-147
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    • 2000
  • This study was conducted to investigate suitable seeding rate under irrigation water-saving rice culture in ridge direct seeding on dry paddy during 1997~1998. Dongjinbyeo was seeded from 60 kg/ha to 120 kg/ha on silty loam condition. The number of irrigation from 3-leaf stage to complete drainage were 7.5 times and total amount of irrigation was 258.75 mm. The number of seedling stand rose with the increase of seeding rate, whereas the rate of seedling stand was decreased with the increase of it. Soil moisture tension was -2kPa at one day after stopped irrigation and lowered to -30kPa at five days after stopped irrigation. Leaf area index and shoot dry weight were increased with rising of seeding rate. Lodging index was increased with the rising of seeding rate, but lodging was not showed in field. Heading date, percent ripened grain and 1,000 grain weight had no difference with seeding rate, and number of spikelets per m$^2$ were highest at the rate of 100 kg/ha. Rice yield was increased by 9% at the seeding rate of 100 kg/ha and 4% at the rate of 80 kg/ha and 120 kg/ha compared with 60 kg/ha. Therefore, it was considered that appropriate seeding rate was 100 kg/ha under water-saving culture in ridge direct seeding on dry paddy.

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Influence of Midsummer Drainage Times on Lodging and Growth of Rice in Direct Drill Seeding Culture on Puddled Soil (벼 무논골뿌림 재배시 중간낙수 회수가 도복 및 생육에 미치는 영향)

  • Kim, Sang-Su;Choi, Weon-Young;Seok, Soon-Jong;Lee, Seon-Yong;Kim, Jong-Ho;Cho, Dong-Sam
    • KOREAN JOURNAL OF CROP SCIENCE
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    • v.40 no.1
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    • pp.33-38
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    • 1995
  • This experiment was conducted to elucidate the effect of the midsummer drainage times on lodging characters, field lodging and yield in direct seeding rice culture in puddled soil. Dongjinbyeo was seeded at May 11 by seeding machine with 4cm of furrow depth and drained, one(50days after seeding DAS)) two (30DAS and 50DAS), and three times (30DAS, and 50DAS and 60DAS). The results are as follows. Culm length was shorten and the wall of N3, N4 were thicken as the drain-age times were increased. As the drainage times were increased breaking weights were increased but the lodging index were decreased. Lodging was occurred seriousely at none drainage, but wasn't occurred two or three times drainage. Yield was higher at 1~2 times drainage compared with none and three times drainage. Therefore, two times midsummer drainage is recommend-able water management method for direct seeding rice culture in puddled soil.

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A Study on Transition of Rice Culture Practices During Chosun Dynasty Through Old References IX. Intergrated Discussion on Rice (주요(主要) 고농서(古農書)를 통(通)한 조선시대(朝鮮時代)의 도작기술(稻作技術) 전개(展開) 과정(過程) 연구(硏究) - IX. 도작기술(稻作技術)에 대(對)한 종합고찰(綜合考察))

  • Guh, J.O.;Lee, S.K.;Lee, E.W.;Lee, H.S.
    • Korean Journal of Weed Science
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    • v.12 no.1
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    • pp.70-79
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    • 1992
  • From the beginning of the chosun dynasty, an agriculture-first policy was imposed by being written farming books, for instance, Nongsajiksul, matched with real conditions of local agriculture, which provided the grounds of new, intensive farming technologies. This farming book was the collection of good fanning technologies that were experienced in rural farm areas at that time. According to Nongsajiksul, rice culture systems were divided into "Musarmi"(Water-Seeded rice), /"Kunsarmi"(dry-seeded rice), /transplanted rice and mountainous rice (upland rice) culture. The characteristics of these rice cultures with high technologies were based of scientific weeding methods, improved fertilization, and cultivation works using cattle power and manpower tools systematically. Reclamation of coastal swampy and barren land was possible in virtue of fire cultivation farming(火耕) and a weeding tool called "Yoonmok"(輪木). Also, there was an improved hoe to do weeding works as well as thinning and heaping-up of soil at seeding stages of rice. Direct-seeded rice culture in flat paddy fields were expanded by constructing the irrigation reservoirs and ponds, and the valley paddy fields was reclaimed by constructing "Boh(洑)". These were possible due to weed control by irrigation waters, keeping soil fertility by inorganic fertilization during irrigation, and increased productivity of rice fields by supplying good physiological conditions for rice. Also, labor-saving culture of rice was feasible by transplanting but in national-wide, rice should not basically be transplanted because of the restriction of water use. Thus, direct-seeded rice in dry soils was established, in which rice was direct-seeded and grown in dry soils by seedling stages and was grown in flooded fields when rained, as in the book "Nongsajiksul". During the middle of the dynasty(AD 1495-1725), the excellent labor-saving farmings include check-rowing transplanting because of weeding efficiency and availability in rice("Hanjongrok"), and, nurserybed techniques (early transplanting of rice) were emphasized on the basis of rice transplanting ["Nongajibsung"]. The techniques for deep plowing with cattle powers and for putting more fertilizers were to improve the productivity of labor and land, The matters advanced in "Sanlimkyungje" more than in "Nongajibsung" were, development of "drybed of rice nursery stock", like "upland rice nursery" today, transplanting, establishment of "winter barly on drained paddy field, and improvement of labor and land-productivity in rice". This resulted in the community of large-scale farming by changing the pattern of small-farming into the production system of rice management. Woo-hayoung(1741-1812) in his book "Chonilrok" tried to reform from large-scale farmings into intensive farmings, of which as eminent view was to divide the land use into transplanting (paddy) and groove-seeding methods(dry field). Especially as insisted by Seo-yugo ("Sanlimkyungjeji"), the advantages of transplanting were curtailment of weeding labors, good growth of rice because of soil fertility of both nurserybed and paddy field, and newly active growth because rice plants were pulled out and replanted. Of course, there were reestimation of transplanting, limitation of two croppings a year, restriction of "paddy-upland alternation", and a ban for large-scale farming. At that period, Lee-jiyum had written on rice farming technologies in dry upland with consider of the land, water physiology of rice, and convenience for weeding, and it was a creative cropping system to secure the farm income most safely. As a integrated considerations, the followings must be introduced to practice the improved farming methods ; namely, improvement of farming tools, putting more fertilizers, introduction of cultural technologies more rational and efficient, management of labor power, improvement of cropping system to enhance use of irrigation water and land, introduction of new crops and new varieties.

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Nitrogen Split Application of Direct-seeded Rice in Tillage and No-tillage Systems (경운과 무경운 조건에서 벼 건답휴립직파재배의 질소분시비율)

  • 이석순;홍승범;백준호
    • KOREAN JOURNAL OF CROP SCIENCE
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    • v.37 no.5
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    • pp.405-412
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    • 1992
  • Growth characters of dry seeded paddy rice was studied at different levels of nitrogen(N) split application (basal : immediately after irrigation : 2 weeks after irrigation: 25 days before heading: heading stage with 10 : 20 : 30 : 20 : 20%, 20 : 30 : 20 : 20 : 10%, 30 : 40 : 0 : 20 : 10%, and 100% basal of slow release urea) in tillage and no-tillage systems. On May 17 in 1990, 6kg /10a of dry seeds of a breeding line of Milyang 95 was broadcasted and covered with a power tiller. Between tillage and no-tillage systems yield and its components, lodging related characteristics, and contents of cellulose, hemicellulose and lignin of culm base were similar. Leaf area index at heading stage was higher in tillage, but lodging index was lower compared with those in no-tillage plot. Culm length, effective tiller ratio, culm base weight, 1000-grain weight, harvest index in slow release N applied plot were higher compared with those in other N treatments. Grain yield of rice among levels of N split applications was similar in tillage, but it was higher in slow release N applied plot in no-tillage if 1kg /10a of additional N was applied as urea at panicle formation stage. At early growth stage N concentration and N uptake were lower in the slow release N applied plot, but higher after heading stage compared with other N treatments. The number of tillers was lowest in slow release N applied plot during the tillering stage, but the number of panicles per hill was similar to other N treatments.

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Appropriateness Evaluation of Plug Seedling Cultivation for Replanting of Rehmannia glutinosa (Gaertn.) Libosch. ex Steud (보식용 지황의 플러그 육묘 재배를 위한 적정성 평가)

  • Lee, Sang Hoon;Kang, Seung Uk;Lee, So Hee;Koo, Sung Cheol;Hur, Mok;Jin, Mei Lan;Lee, Woo Moon;Park, Min Su;Kim, Yeon Bok;Han, Jong Won
    • Korean Journal of Medicinal Crop Science
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    • v.27 no.3
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    • pp.202-207
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    • 2019
  • Background: Rehmannia glutinosa is a perennial herb belonging to the family Scrophulariaceae and is used in traditional oriental medicine. This study was conducted to evaluate the appropriateness of plug-seedling cultivation for replanting of R. glutinosa. Methods and Results: The seed rhizomes of Rehmannia glutinosa 'Jihwang 1' were harvested in the middle of March, 2018. Direct seedling cultivation was conducted after air curing for 3 days. The seedlings for transplanting were cultivated for 30 (30D), 45 (45D), and 60 days (60D). The mat formation rates of the 30D, 45D and 60D treatment seedling were 81.3%, 100%, and 100%, respectively. Of the tree treatment groups, flowering occurred only in the 45D and 60D treatment groups, and their flowering rates were $7.3{\pm}3.06%$ and $13.3{\pm}1.15%$, respectively. The agronomic characteristics and active components of the three treatment groups were evaluated in comparison with the DS1 (directly seeded group, control) and DS2 (directly seeded group, replanting) groups. As a result, the leaf length and leaf width of the 30D seedlings were higher than other treatment groups, but the number of leaves per plant was statistically the same. In addition, root diameter and yield of the 30D seedling were statistically the same as DS1. Moreover the catalpol contents of 30D, 45D, DS1 and DS2 group seedlings were 2.23%, 1.86%, 2.50% and 2.08%, respectively. Conclusions: Taken together, these findings suggest it is feasible to use the plug-seedling cultivation method for replanting of R. glutinosa. seedlings. However, further evaluation of the economic aspect is needed.

Changes of Rice Yield and Soil Physicochemical Properties in Long-term Dry Seeded Rice-Barley Double Cropping (건답직파 벼-보리 장기간 이모작 재배시 벼 수량 및 토양 물리화학성 변화)

  • Shin, Sang-Ouk;Park, Sung-Tae;Hwang, Chung-Dong;Hwang, Dong-Yong;Kim, Sang-Yeol;Moon, Huhn-Pal
    • KOREAN JOURNAL OF CROP SCIENCE
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    • v.46 no.6
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    • pp.459-463
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    • 2001
  • Changes of rice yield and soil physicochemical properties of the dry-seeded rice-barley double cropping system were investigated for 10 years from 1990 to 1999. Generally, seedling stand was more unstable in the rice-barley cropping system regardless of barley straw addition or removal than in the rice single cultivation as indicated by higher standard deviation of seedling stand across year. Rice yield in rice-barley double cropping cultivation was increased due to barley straw application starting from the second year, recording 2 to 19% increase (average of 9% for 10 years) due to higher spikelet number. Protein content and Mg/K equivalent ratio were similiar among the barley straw applied field, rice single crop and barley straw removed plots. Also, amylose content was not significantly different among cropping patterns. Physicochemical properties of soil was improved by applying the barley straw; soil porosity was higher and content of organic matter and cation exchange capacity of Ca increased but those of Mg and K did not differ.

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Changes in Chemical Components of Stagnant Water by Tillage Method and Amount of Nitrogen Application in Wet Seeded Rice after Barley Straw Mulching (논에 보리짚 시용시 경운방법 및 질소시비량에 따른 논물의 화학성분 변화)

  • Cheong, Jin-Il;Choi, Min-Gyu;Noh, Tae-Hwan;Lee, Jung-Ho;Kwon, Tae-Ohu
    • KOREAN JOURNAL OF CROP SCIENCE
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    • v.41 no.4
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    • pp.411-419
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    • 1996
  • The experiment was aimed to determine a change of chemical component in irrigatted water based on different tillage methods and nitrogen rates under mulching of barley straw in direct seeded rice. There was no difference in water pH of no-tillaged plot but high in tillaged plot until 10 days after treatment. The electric conductivity(EC) of the water was higher in no-tillaged plot than in tillaged plot. However, the dissolved oxygen content was vice versa. The content of NH$_4$-N was high in higher application rate of N fertilizer without the tillage. Mean while, NO$_3$-N content was highly affected by no-till aged plot particularly in between application time and fertilizer rate but not in tillaged plot. There was higher in P043- content with the no-tillaged plot compared to the tillaged plot. It was big difference with higher application rate of the fertilizer. Soil cations were high in much application of fertilizer without the tillage.

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