• Journal of Aquaculture
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• v.22 no.1
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• pp.42-50
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• 2009

Shrimp farming which is entirely conducted in outdoor ponds in the west coast of Korea has been suffered from mass mortality due to viral epizootics. Intensive indoor shrimp culture under limited water exchange can solve these problems of outdoor ponds including viral transmission from environment, pollution due to discharge of rearing water, low productivity and limited culture period. In this study, juvenile L. vannamei (B.W. 0.08-0.09 g) was stocked with $3,000-5,455/m^3$ in density in four raceway tanks (two $12.9\;m^2$, two $18\;m^2$ tanks) and cultured for 42 days with 2.7-3.4% of daily water exchange. Results from four tanks showed FCR of 0.79-1.29, survival of 38.2-48.0%, and yields of $2.49-4.22\;kg/m^3$ which is consistent with 12-20 and 8-14 times higher than those of commercial shrimp hatchery and outdoor pond in Korea, respectively. Concentrations of total ammonia nitrogen in all four tanks were 1.11-1.42 ppm in mean level and did not exceed 6.0 ppm (0.096 ppm of $NH_3$) which is still acceptable levels for shrimp growth. During the culture trial, concentration of $NO_2$-N rapidly increased from stocking, resulting in mean concentration of 18.45-22.07 ppm. It also exceeded 10 ppm over four weeks and maintained at 35-45 ppm for four days in all tanks, accounting for low survival of shrimp due to long-term exposure to high concentration of $NO_2$-N. Nevertheless, the results with survival rate over 38% from raceways which experienced the extreme $NO_2$-N levels suggests that under "biofloc system" white shrimp can acclimate to high $NO_2$-N concentration to some degree.

• Korean Journal of Soil Science and Fertilizer
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• v.27 no.1
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• pp.54-63
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• 1994

Runner-derived(Expt.1) and tissue culture-derived strawbeery plantlets(Expt. 2) were grown in pots under greenhouse condition and inoculated with inocula of the vesicular-arbuscular mycorrhizal(VAM) fungi isolated from a field strawberry plants. Total biomass of mycorrhizal strawberry plants was significantly increased. There was a similar tendency in the number of cluster and flower at 20 weeks after inoculation, and VAM fungi inoculation positively influenced the leaf number, leaf length, leaf width and petiole length of strawberry plants in all investigated times. However, no difference was in the flowering time of strawberry plants. Leaf margin of non-inoculated strawberry plantlets turned into raddish brown(7.5R 4/8) from around 4 weeks after habituation. Inoculation of VAM fungi at the time of habituation was much more effective in stimulating plant growth. VA mycorrhizal dependency were 162.7 % in the runner-derived strawberry plants, Dependency with pre-and post-habituated incoulation in tissue culture-derived plants was respective 116.4% and 106.0%. The levels of mycorrhizal colonization were increased with plant growth and infection rates by endophytes at harvest time were 47.5% in Expt. 1, 56.4% in Expt. 2, respectively. Contents of phosphorus, potassium and calcium in mycorrhizal strawberry plants at harvest time were higher than non-mycorrhizal ones however, magnesium concentration was decreased. These experiments demonstrated that VAM fungi could be introduced into nursery stages of strawberry plantlets including the temporary planting period to improve growth and plant nutrients uptake by mycorrhizal plants.