• Korean Journal of Weed Science
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• v.12 no.2
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• pp.124-131
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• 1992

Not only reducing the carry-over effects of quinclorac [3, 7-dichloro-8-quinoline carboxylic acid] used in paddy field to some following vegetable crops but also rationalizing agro-ecology conservation and farm economy, the reducing feasibility of application rates by various cropping patterns and application timing after rice seeding and transplanting. Four cropping patterns namely dry direct seeding(DDS), flooded direct seed(FDS), transplanting of 8 days old early seedlings(EST) and 25 days old machinery seedling(MST) were experimented with 7 application timings as 0, 5, 10, 15, 20, 25, 30 days after seeding/transplanting and 9 levels of application rates as 0, 75, 150, 225, 300, 375, 450, 525, and 600g ai/ha of the chemical, respectively. Within the maximum permitted limit of rice phytotoxicity, the minimum application rate of quinclorac to complete control of Echinochloa crus-galli as influenced by various cropping patterns with application timing could be evaluated as follows : A. Dry direct seeding : The minimized application rate at application timing upto 10 days after seeding (DAS) was counted 150g ai/ha, and delaying upto 15-30 DAS, the rates were increased upto 225-525g ai/ha. B. Flooded direct seeding and transplanting : The application rates were minimized 75g ai/ha at application timing upto 10 days after seeding/transplanting(DAS/T), 150g ai/haupto 15 DAS/T, and 225g ai/ha at later than 20 DAS/T, respectively.

• Journal of Bio-Environment Control
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• v.28 no.4
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• pp.342-351
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• 2019

The optimum N concentrations incorporated as pre-planting nutrient charge fertilizer were determined for seedling raising using cylindrical paper pots. A root medium was formulated by blending of peat moss (particles smaller than 2.84 mm were 80-90%) and perlite (1 to 3 mm) with the ratio of 7:3 (v/v). The treatment N concentrations incorporated during the root medium formulation were adjusted to 0, 150, 250, 500, and $750mg{\cdot}L^{-1}$ and the concentrations of essential nutrients except N were equal in all treatments. After making of paper pots and putting into the 40-cell tray, the seeds of Chinese cabbage ('Chunmyeong Bom Baechu') and pak-choi ('Hanog cheonggyeongchae') were sown. During the raising of seedlings, weekly analysis of medium pH, EC and concentrations of inorganic elements were conducted. After 21 and 20 days after seed sowing of Chinese cabbage and pak-choi, the growth of the above-ground parts were measured and contents of inorganic elements in the plant tissues were analyzed. During the growing period, pH of the root media rose gradually and the EC decreased rapidly at week 3. The pH of root media at harvest was in the range of 5.3 to 5.9 in Chinese cabbage and 4.93 to 5.39 in pak-choi. Growth of the aboveground parts in terms of fresh and dry weight in both the plants were the highest in the $250mg{\cdot}L^{-1}$ N treatment and the lowest in the control treatment. The elevation of pre-planting N concentrations in root medium resulted in the increase of tissue N content and decrease of P, Ca, and Mg contents. The regression equation derived from the influence of varied pre-planting N concentrations on dry weight of above-ground tissue were $y=-0.0036x^2+0.0021x+0.0635$ ($R^2=0.9826$) in Chinese cabbage and $y=-0.16x^2+0.0009x+0.032$ ($R^2=0.991$) in pak-choi. When the low critical concentration of pre-plant N is taken at the point where dry weight of above-ground tissue is 10% less than maximum (0.40 g in Chinese cabbage and 0.16 g in pak-choi), those point are 0.36 g and 0.144 g per plant in Chinese cabbage and pak-choi, respectively. The lower critical N concentrations of root media calculated from the regression equations are $196mg{\cdot}L^{-1}$ for Chinese cabbage and $187mg{\cdot}L^{-1}$ for pak-choi. These results indicate that optimum pre-plant N concentrations for seedling raising using paper pots are in the range of 196 to $250mg{\cdot}L^{-1}$ for Chinese cabbage and 187 to $250mg{\cdot}L^{-1}$ for pak-choi.