• Korean Journal of Soil Science and Fertilizer
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• v.38 no.6
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• pp.328-333
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• 2005

Ammonia volatilization is the major form of nitrogen (N) loss from flooded paddy soils and causes low N use efficiency. The effects of controlled release fertilizer (latex coated urea complex fertilizer, LCU) on reducing N loss by ammonia volatilization was measured comparing with urea in rice culture system of direct seeding on dry soil. In the treatment of urea, $NH_4-N$ concentration in surface water after flooding increased rapidly up to $8-10mg\;L^{-1}$ as affected by topdressing, while in the LCU treatment $NH_4-N$ concentration in surface water was less than $1mg\;L^{-1}$ during rice growing season. Relation of $NH_4-N$ concentration in surface water and ammonia volatilization was significant in urea treatment. The amount of ammonia volatilized from rice paddy of LCU treatment was $2.4-3.0kg\;ha^{-1}$ and the rate of ammonia volatilization from N fertilizer applied was only 2.0-2.3% compared with 5.9-7.9% in urea treatment. Therefore, N loss by ammonia volatilization could be reduced by 72-76% with by LCU compared with urea in rice culture system of direct seeding on dry soil.

• 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.

• Korean Journal of Environmental Agriculture
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• v.17 no.3
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• pp.227-233
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• 1998

To mitigate the methane emission from rice paddy fields, effects of nitrogen fertilizers source and cultural patterns were evaluated on silty loam soils. And a pot experiment was carried out to find out the effects of nitrogen fertilizers on soil pH, Eh, sulfate concentration of soil water in flooded soil. In transplanting cultivation, the total methane emission depending on fertilizers was $32.9gm^{-2}$ for urea ; $30.3gm^{-2}$ for ammonium sulfate ; $26.4gm^{-2}$ for coated urea. Methane emitted in direct seeding on dry soil was $24.7gm^{-2}$ for urea ; $16.7gm^{-2}$ for ammonium sulfate : and $22.8gm^{-2}$ for coated urea. Thus, the methane emission rate of direct seeding on dry soil was 29.7% lower than transplanting. According to the nitrogen fertilizers, the methane emission rate by ammonium sulfate and coated urea were reduced 18.4 and 15.9% in comparison with urea, respectively. In pot experiments, pH in flooded soils depending on nitrogen fertilizers dereased in order of urea > coated $urea{\fallingdotseq}no$ fertilizer > ammonium sulfate and the order was coincided with that of total $CH_4$ emission from flooded soil. Soil Eh was highest in ammonium sulfate application followed by coated urea, no fertilizer, urea. And sulfate concentrations of soil water were in order of ammonium sulfate > coated urea > urea > no fertilizer.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.37 no.5
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• pp.442-448
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• 1992

In order to determine the critical seeding date in dry paddy field at southern plain area of Gyeongbug province, dry seeds of three different rice cultivars was sown April 25 to June 20 at 15 or 10-day intervals. The number of days from seeding to emergence decreased in late seeding date : from 32 days at April 25 to 7 days at June 10 sowing. The number of seedlings showed 121-154 plants per square meter were not much differed among the varieties and seeding dates. Culm length, panicle length and ripened grain ratio decreased in late seeding date, but number of panicles per square meter, 1,000 grain weight and spikelets number per panicle were similar among the seeding dates. The cumulative effective temperature(mean air temperature-15$^{\circ}C$) from emergence to heading was very constant having 655$\pm$9$^{\circ}C$ in Keomhobyeo, 771$\pm$9$^{\circ}C$ in Donghaebyeo and 801$\pm$3$^{\circ}C$ in Milyang 95, respectively. Grain yield of Dong Haebyeo seeded in June 20 and Milyang 95 seeded in June 10 were much lower compared with other seeding dates and increased green kernel in late seeding date of Donghaebyeo and Milyang 95.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.43 no.1
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• pp.32-37
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• 1998

The objective of this study was to analyze lodging-related traits using different cultivars from Korea, Japan, and the U.S. in direct seeded rice on dry paddy field. Stem diameter and culm wall thickness were highest in 'Caloro' followed by 'Nongan', 'M202', and 'Calrose'. All the U.S. cultivars were higher than the others in stem diameter and culm wall thickness. These two traits were important with regard to lodging. The highest breaking strength (1442g) was observed in Caloro. 'Gancheoek', 'Dongjin', and transplanted 'Hatsuboshi' showed more than 1000g in breaking strength. Lodging index was lowest in Hatsuboshi followed by Nongan and Gancheok. Even though breaking strength of the U.S. cultivars was higher than others, their lodging index values were high. There were no statistically significant differences in starch content. However, Calrose, Caloro, Dongjin, and Koshihikari were relatively higher than others in starch content. Positive correlations were found between culm base weight, lignin and breaking strength. High contents of lignin and cellulose were observed in Nongan, transplanted Hatsuboshi, Calrose, and Caloro. Traits such as stem diameter, culm wall thickness, bending moment, culm length, breaking strength, cellulose, lignin, and culm base weight were closely related to a lodging index. According to path coefficient analysis, most important traits were culm length, stem diameter, thickness of clum wall, and top plant weight.

• Korean Journal of Soil Science and Fertilizer
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• v.31 no.4
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• pp.324-329
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• 1998

To investigate the changes of $NH_4-N$ in soil, nitrogen uptake by rice plant, nitrogen use efficiency and rice yield by the application of Latex Coated Urea(LCU) on direct seeding rice, rice was planted on paddy field, Jeonbuk series at the Honam area, from 1996 to 1997. Nitrogen in LCU applied as basal dressing in whole layer was dissolved almost untill non-productive stage. Thus, nitrogen deficiency symptom appeared and N in shoot was 1.75% showing 28.1 of SPAD value at heading stage. However percentage recovery of fertilizer N was higher in LCU than with urea application. Top dressing of urea at panicle initiation stage in addition to basal dressing of LCU, increased rice yield by 9%. Conventional split application of urea on the surface decreased the percentage recovery of fertilizer N to 56.9% of whole layer application plot.

• Proceedings of the Korean Society of Crop Science Conference
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• 2005.04a
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• pp.298-299
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• 2005

• Proceedings of the Korean Society of Crop Science Conference
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• 2001.05a
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• pp.96-97
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• 2001

• KOREAN JOURNAL OF CROP SCIENCE
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• v.38 no.2
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• pp.174-182
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• 1993

Performance of 3 indica ${\times}$ japonica(Chilseungbyeo, Samgangbyeo, and Gayabyeo), 7 japonica(Yeongsanbyeo, Yeongdeugbyeo, Hwajinbyeo, Palgongbyeo, Seumjinbyeo, Tamjinbyeo, and Milyang 95), and 2 indica(Tebonnet and Lemont) rice varieties was tested at 1, 3, 5, and 7cm seeding depths in a growth chamber and field. In the growth chamber the number of days from seeding to seedling emergence increased as seeding depth increased, while percent germination and emergence and emergence / germination ratio decreased. However, in the field seedling emergence at 1em seeding depth delayed slightly compared to 3cm probably due to lack of soil moisture. The number of seedlings and maximum tillers at 1, 3, and 5cm seeding depths was similar, but it was higher compared to 7cm seeding depth. Yield and yield components were similar among the seeding depths when all the varieties averaged although 1,000-grain weight was slightly higher at 7cm deeding depth compared to others. At 1cm seeding depth the length of mesocotyl of all varieties was similar and ranged 0.1-0.2cm and that of coleptile ranged 0.8-1.1cm. As seeding depth increased up to 7cm Tebonnet which showed the highest percent emergence emerged by elongation of both mesocotyl and coleoptile, while the other varieties emerged largely by elongation of coleoptile.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.44 no.3
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• pp.221-224
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• 1999

A field experiment was carried out to observe the weed control effects of vetch and to evaluate vetch characteristics on clay loam soil in no-till direct-sown rice-vetch cropping systems. The effects of weed control, forage productivity, and N content of vetch plants were investigated. With the progress of plant growth, density of Chinese milk vetch (Astragalus sinicus L.) gradually decreased, but densities of foxtail and other weeds decreased steeply due to the depression by the over-shaded vetch canopy in a no-till direct-sown rice-vetch cropping paddy field. The vetch density in tillage systems was lower than in notillage cropping systems. Lower vetch density occurred with an increase in foxtail density and other weeds. Weed control effect increased by the progress of vetch growth, which indicated that the vetch canopy over-shaded the weeds. Vetch straw was degraded rapidly submergence after with water at the time of wet sowing of rice. Early harvesting of vetch seed resulted in lower seed germination. To acquire enough seedlings without re-sowing, the harvesting of seed should be delayed at least 28 days after the flowering stage in order to ensure the vetch population is sustainable in a no-till direct-sown rice-vetch cropping system. In order to improve the survival of vetch plants, vetch seeds should germinate from the heading .stage to before the full-ripening stage of rice plants. To enhance the percent of over-wintering survival, vetch seeds should germinate no later than the end of October in southern Korea. The dry weight of vetch plants increased with the progress of vetch growth until the flowering stage but N content decreased for 30 days from before the flowering stage (2.9%) until the ripening stage (1.8%). We concluded that Chinese milk vetch could have an effect on weed control before the flowering stage, sustainability without re-sowing of seed annually, and effective green manure for rice pre-crop in no-till direct-sown rice-vetch relay cropping systems.