Experiments were conducted to find out the optimum level of slow release N fertilizers when total amounts of nitrogen required throughout the growing season in paddy were applied in the soil of seedling box. To evaluate the emergence rate and growth of rice seedlings, five levels of Meister (MS) 10, MS S10, and latex coated urea (LCU) which are equivalent to 0, 40, 60, 80, and 100kg N h a-l were mixed in soil of the seedling box. Emergence rate differed depending on the fertilizers and N levels; in MS 10 plots the emergence rate was 40.8% at 40kg N h a-l and no seedlings were emerged at the higher levels, in MS S10 plots higher than 80% at all the N levels, and decreased with the N levels from 70.0% at 40 kg N h a-l to 59.5% at 100kg N h a-l of LCU. Seedling started to wilt at 40 kg N h a-l of MS 10 and 80 and 100 kg N h a-l N of LCU on the 8th day after sowing, while seedling growth was normal at all the levels of MS S10. Field performance of rice was evaluated at the 0, 30, 60, 90, 120kg N h a-l of MS S10 applied in the soil of seedling box and N was not applied in paddy. Grain yield at 90 and 120kg N h a-l of MS S10 was similar to conventional urea split application (120 kg N h a-l ), but significantly higher compared to 30 and 60kg N h a-l of MS S10. Fertilizer N recovery decreased with N levels and the N recovery at 90 kg N h a-l of MS S10 and conventional urea split application were 62.2 % and 44.2%, respectively, with similar grain yield. The optimum level of MS S10 to be applied in seedling box seems to be about 90 kg N h a-l considering grain yield, price of fertilizer, labor applying fertilizer, and fertilizer N recovery.d fertilizer N recovery

This experiment evaluates wintering ability to maintain green color of lawn grasses during winter and investigates the effects of top dressing of fertilizer on improving green color during regrowth. Kentucky blue-grass could maintain green color and leaf chlorophyll content better than tall fescue and creeping bentgrass in winter. All three grasses in this experiment have shown the excellent wintering ability. In enhancing the recovery of green color at the early stage of regrowth, the mulching effect with rice straw was highly significant for creeping bentgrass. Green color recovery in grasses during its regrowth was better at the top dressing plots than at the plots without top dressing, but when fertilizer application levels were increased, green color in lawn grass did not significantly change. Although green color in tall fescue, Kentucky bluegrass, and Korean lawngrass could be maintained during summer, the green color of creeping bentgrass is reduced significantly with high temperature. Top dressing after winter and mowing improved leaf chlorophyll content and green color in tail fescue and Kentucky bluegrass significantly. However, Korean lawngrass did not respond significantly with increased levels of fertilizer.

The viviparity of 28 rice varieties was tested at 25 days after heading(DAH), 35DAH, and 45DAH in the laboratory and field condition for 12 days. The incubation temperature was 20/l0~circC (day/night), 25/15~circC and 30/20~circC in the laboratory test, and under field water conditions in the field test. The biggest varietal difference of viviparity was found in the laboratory test when examined at 45DAH with the 6-day incubation under 25/15~circC . At this conditions the mean viviparous ratio was 32.1 % with the range of 53.9 and the variance of 259.5. In the field test, the significant varietal difference in the viviparity was also found in the lodging treatment at 45 DAH for 6 days. Correlation coefficient analysis between the field and laboratory tests was highly significant from 4 days after incubation at 45 DAH and after 6-day incubation at 35 DAH, and correlation coefficient was higher as incubation days in the laboratory and submerged days under field water became longer. Considering the correlation between the field and laboratory tests, varietal difference of viviparity and convenience of testing, the laboratory test at 45 DAH for 6-day incubation under 25/15~circC was the most efficient evaluation method for the viviparity of rice cultivar

Viviparous germination causes yield loss and quality deterioration of rice. This study was conducted to investigate varietal differences of the viviparous germination with different days after heading (DAH) and different temperatures. In the laboratory examination, the averaged germination rate of all varieties at 45DAH and at 25DAH was 79.9%, and 27.5% under the incubation at the temperature of 30~circC /20~circC (day/night) for 12 days. Andabyeo, Da- sanbyeo, and Nonganbyeo showed the lowest viviparous germination rates among the tested varieties. The shoot length of the viviparous germination measured 12days after incubation at 30/20~circC ranged from 21 to 53mm, indicating significant deterioration of rice quality. In the field test, the averaged viviparous germination rates of rice varieties at 25, 35, 45DAH with the underwater conditions for 4 days were 2.2, 6.2 and 9.2%, respectively, while their rates at 12 day after underwater conditions increased to 17.6, 44.2 and 43.8%, respectively. A variety that showed the highest viviparous germination rate at 25 and 35 and 45DAH was Heukjinjubyeo. When standing rice panicles without lodging were examined after consecutive raining for 7 days Juanbyeo showed the highest viviparous germination (45.5%), followed by Odaebyeo (16.0%), Jinbubyeo (14.5 %), Bongkwangbyeo (14.2 %) and Obongbyeo (12.6%). The viviparous germination of rice was greatly affected by variety, days after heading and temperature settings. Bongkwangbyeo, Juanbyeo, Dongjinbyeo, Hwasunchalbyeo, Naepoongbyeo and Heukjinjubyeo were classified as the most susceptible varieties to the viviparous germination in the field conditions.

In order to identify the responses of Korean soybean cultivars to sudden death syndrome (SDS), forty-two Korean cultivars and three check cultivars (Hartwig and PI 520733 are resistant; Hartz 6686 is susceptible) were tested with sorghum seed inoculum infested with Fusarium solani f. sp. glycines isolate 171 in the greenhouse. This isolate has blue pigment cultural shape on potato dextrose agar (PDA) medium. All Korean cultivars inoculated with F. solani isolate 171 showed the typical SDS symptoms and disease severity on soybean leaves in each cultivar varied at 4 weeks after inoculation. Nine cultivars were included in the most SDS susceptible group and six cultivars were included in the most susceptible group based on Duncan＇s multiple range tests (P~leq 0.05). In results of the LSD analysis for SDS the resistant group, a total of twenty-five Korean cultivars were included in the same SDS resistant group as PI 520733 or Hartwig and fourteen Korean cultivars were included in the same SDS susceptible group as Hartz 6686. In the second experiment, ten Korean cultivars, ten U.S. cultivars, and one introduced line were compared in the same way as the first experiment Disease severity ranking of check cultivars, Hartwig, PI 520733, and Hartz 6686, were the same as in the first experiment. Within Korean cultivars, seven cultivars showed the consistent severity proportions of leaf symptoms. Disease rankings of these cultivars in this experiment were the same as those in the first experiment. Three US cultivars: Hartwig, Hartz 5454, and Forrest, three Korean cultivars： Keunolkong, Myeongjunamulkong, and Jinpumkong 2, and one introduced line, PI 520733, were included in the highest SDS resistant group. Shinphaldalkong 2, Milyang 87, and Samnamkong consistently showed the highest SDS susceptibility in both experiments. Average disease severity in the first and the second experiment were 49.56% and 45.39%, respectively.

This study examined the effects of growth retardants and midsummer drainage on lodging-related characters in direct seeding rice culture on flooded paddy surfaces. Treatments included in this study were continuous flooding, two time midsummer drainages (TTD), and inabenfide or trinexapac-ethyl application after TTD. Culm length was reduced most by 11.4cm in trinexapac-ethyl treatment after TTD, followed by 4.1cm in inabenfide treatment after TTD compared to TTD treatment. A significant reduction in culm length occurred at the 3rd internode in inabenfide treatment applied at 40 days before heading (DBH), while trinexapac-ethyl application at 8 DBH reduced the 3rd>2nd>1st internode. The culm diameter of the 4th internode was increased by the application of trinexapac-ethyl following TTD compared to TTD treatment. Thickness of culm wall was significantly increased by trinexapac-ethyl but not by inabenfide applications. Lodging index was the highest in continuous flooding and the lowest in trinexapac-ethyl treatment after TTD. Subsequently, field lodging did not occur in plots treated by trinexapac-ethyl. Rice plants subjected to midsummer drainage or growth retardants showed higher ripened grain ratio and 1000-grain weight, resulting in higher rice yield. These results indicate that trinexapac-ethyl, which can be applied at the relatively later growth stage after proper judgement of lodging occurrence, could be a useful tool for reducing lodging in direct seeding rice culture on flooded paddy fields

The objective of this study was to ,determine trinexapac-ethyl [4-(cyclopropyl- α -hydroxy-me-thylene)-3,5-dioxocyclohexanecarboxylic acid ethyl ester] effects on lodging-related traits of rice varieties treated at different application rates and times. Trinexapac-ethyl WP was applied at the rate of 10, 20 and 30g ai/l0a to Heukjinjubyeo and Daeanbyeo, respectively. Effects of trinexapacethyl varied greatly with application time as well as application rate with little differences between rice varieties. As the application rate increased, lodging index, center of gravity and exsertion of panicle above flag leaf decreased, whereas breaking strength and phytotoxicity increased. Exsertion of panicle was greatly influenced by the application time with a little difference by application rate. The most effective application time of trinexapac-ethyl based on lodging index and total internode length (Ist-4th node) was 2DBH(days before heading) in Heukjinjubyeo and 17DBH in Daeanbyeo, resulting in reducing total internode length by 12.9 and 9.7cm, respectively. A significant reduction was found at the 1st, 2nd, and 3rd internodes in Heukjinjubyeo, while at the 2nd and 3rd internodes in Daeanbyeo. No significant difference was found among treatments in the panicle length of both rice varieties but the panicle fresh weights of Daeanbyeo were significantly greater in all trinexapac-ethyl treatments compared with that of the control when measured 20 days after heading. Consequently, trinexapacethyl treatment significantly improved lodging-related traits of rice plants without affecting rice yield and yield components