• Korean Journal of Weed Science
• /
• v.18 no.2
• /
• pp.116-121
• /
• 1998

Field experiment were carried out to elucidate the changes of weed occurrence according to the sowing time and to establish the efficient weed control system in dry seeded rice cultivation. E crus-galli and D. sanguinalis are tow major weeds at the earlier sowings, but C. difformis was dominating at the later sowing. In the case of E. crus-galli, there was a tendency of gaining its dominance values as the rice growth stage advances. The later the sowing time was, the more weeds occurred at the early rice growth stages: However, when measured at heading, total dry weight was greater at the earlier sowings. Yield loss due to weeds were also greater at the earlier sowings. Community diversity of weeds was greater at the later sowings, while specific weed was gradually dominating as rice growth stage advances, regardless of sowing time. When herbicides were applied before 15 DAS, weeds were effectively controlled only upto 35 DAS. So systemic herbicide application, one on 0 to 10 DAS and the other on just after flooding, appeared to be recommendable in direct seeded rice cultivation.

• Journal of The Korean Society of Grassland and Forage Science
• /
• v.34 no.4
• /
• pp.234-239
• /
• 2014

This experiment was conducted to evaluate the effect of seeding rates on the forage quality and productivity of direct-seeded whole crop rice at the experimental field of the Grassland and Forages Division, National Institute of Animal Science, RDA from 2007 to 2008. Whole crop rice variety, "Nokyang", developed by the National Institute of Crop Science, was directly seeded with four different seeding rates (30, 60, 90 and 120 kg/ha). There were no significant differences (p<0.05) found in emergence date, heading date, greenish and disease resistance based on the seeding rates. Plant height increased at higher seeding rates but the tiller number per plant decreased (p<0.05). The dry matter (DM) content showed no significant difference based on seeding rates (p<0.05) while the yield of fresh and dry matter increased with incremented seeding rates (p<0.05). Acid detergent fiber (ADF) content increased with higher seeding rates, but the neutral detergent fiber (NDF) content did not show a similar tendency. The total digestible nutrient (TDN) content was lowest with 120 kg/ha seeding rate. The grain ratio decreased at higher seeding rates. In economic analysis, the plot seeded at a rate of 60 kg/ha showed the highest income increment. Although high seeding rates increased the DM yield, a seeding rate of 60 kg/ha is recommended as the proper seeding rate for direct-seeded whole crop rice.

• KOREAN JOURNAL OF CROP SCIENCE
• /
• v.43 no.2
• /
• pp.124-127
• /
• 1998

Since weedy rice problems have emerged with the recent advent of direct seeding cultivation in Korea, the establishment of effective control strategies for weedy rice is considered to be one of the urgent issues to be solved for widely practiced direct seeding rice cultivation. A three year experiment was conducted to investigate the occurrence pattern of weedy rice in four different rice cultivation practices: high ridged dry seeding, wet drill seeding, water seeding, and machine transplanting. The highest weedy rice occurrence of 11.0% was observed in high ridged dry seeding practice followed by 9.6% in wet drill seeding, 6.4% in water seeding practice, and 0.2% in machine transplanting practice, respectively. The same trend was observed when we examine the occurrence of contamination of panicle and rice grain by weedy rice. More contamination was observed in high ridged dry seeding than any other practices. It was also found that the possible emergence depths from the soil surface was deeper in both in ridged dry seeding and wet drill seeding practice (0-5 cm from the soil surface) than those in water seeding (0-4 cm), and machine transplanting practice (0-3 cm). The highest yield reduction of 19.5% was observed in high ridged dry seeding practice followed by 13.0% in wet drill seeding, 6.3% in water seeding practice. The reduction may have occurred to the competition between weedy rice and cultivated rice, These findings suggest that among the four cultural practices examined, the machine transplanting practice is the most effective method to control and reduce the weedy rice occurrence and weedy rice seed in soil.

• Korean Journal of Weed Science
• /
• v.11 no.3
• /
• pp.178-186
• /
• 1991

This study was conducted to evaluate the major weeds occurred in direct seeded rice and their compition with rice, and to establish the effective weed control method. The important weeds occurring in dry direct seeded rice were Echinochloa crusgalli, Cyperus amuricus, Rorippa islandica, etc. Among them, Echinochloa crusgalli was the most dominant weed species. In view of the Simpson's dominance index, the maximum number of the weeds was observed at 30 days after seeding, showing 0.26, but decreased as the time passed. In other hand, Simpson's dominance index of weed dry weight increased from 0.09 at 15DAS(days after seeding) to 0.28 at 60DAS indicating that particular weed such as barnyardgrass was dominating the fields. The plant height and the tiller number of rice in the dry direct seeded rice were not greatly affected by the time and duration of competition with weeds, but rice yield was greatly influenced by them. The yield reduction was observed when compition between rice and weeds were initiated at 20 to 40 DAS till the harvesting time. The highest weed control efficacy was observed at the treatment of systematic herbicide application such as soil applied Butachlor followed by Mefenacet/Bensulfuron-methyl/Dymron at 30 DAS after seeding, and soil applied Dimepiperate/Bensulfuron-methyl mixture as a preemergence type gave also an excellent control.

• KOREAN JOURNAL OF CROP SCIENCE
• /
• v.42 no.6
• /
• pp.752-758
• /
• 1997

Urea, which is the major nitrogenous fertilizer used in Korea, has been used inefficiently in direct-seeding on dry soil by farmers. This study was conducted to investigate changes in concentrations of basal N within soil layers and its loss during early stage of rice growth. Urea fertilizer was applied in the rates of 7, 5.25, 3.5, 1.75, 0kg- N /10a under direct-seeded rice in dry paddy soil. The concentrations of ammonium and nitrate were determined in soil samples with different depths during period from seeding to the 3rd leaf stage. Futhermore, N leaching was measured in lysimeter designed with pot in greenhouse. ${NH_4}^+ \; and\; {NO_3}^-$ adsorption by soil increased with increasing concentration of added urea and decreased as deeper in soil layers. ${NH_4}^＋$ concentration reached its peak at 7 days after urea application (DAA) and disappeared almostly at 14 DAA. ${NO_3}^-$ reached its peak at 10 DAA and decreased slowly until 14 DAA. ${NO_3}^-$N leaching started next day after urea application and completed until 11 DAA. We concluded that most of basal N applied to direct-seeded paddy was lost by leaching and not useful for rice plant which was in stage of germination. It is urgent need to develop new nitrogen application method for direct-seeding rice on dry soil.

• Korean Journal of Weed Science
• /
• v.17 no.3
• /
• pp.281-287
• /
• 1997

Growth and anatomical responses of rice and barnyardgrass(Echinochloa crus-galli) to oxyfluorfen were examined under various growing conditions in a greenhouse. With foliar application at 0.08kg ai/ha 7 days after seeding or transplanting, oxyfluorfen completely reduced the shoot and root growth of barnyardgrass under all growing conditions. However, oxyfluorfen reduced the growth of direct seeded and transplanted rice by 0~64% and 0~12%, respectively. Phytotoxic effect on rice growth, with respect to plant height and shoot fresh weight, was more pronounced under water(53~63%) than under dry-condition(16~33%), and in broadcast-seeded(34~62%) than in drill-seeded rice(16~33%). Anatomical changes of epidermal and vascular bundle sheath cells of rice leaves were not induced by oxyfluorfen, but mesophyll cells were partially ruptured and total leaf thickness was reduced. Oxyfluorfen, however, constricted and ruptured mesophyll and vascular bundle sheath cells and severely reduced leaf thickness of barnyardgrass under all growing conditions examined. These anatomical changes were more severe under dry- than under water-seeded condition.

• Proceedings of the Korean Society of Crop Science Conference
• /
• 1991.05a
• /
• pp.74-75
• /
• 1991

• Proceedings of the Korean Society of Crop Science Conference
• /
• 1994.06a
• /
• pp.108-109
• /
• 1994

• Proceedings of the Korean Society of Crop Science Conference
• /
• 1999.05a
• /
• pp.82-83
• /
• 1999

• Proceedings of the Korean Society of Crop Science Conference
• /
• 1999.05a
• /
• pp.84-85
• /
• 1999