• The Korean Journal of Pesticide Science
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• v.3 no.2
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• pp.29-36
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• 1999

The leaching behaviour of $^{14}C$-paraquat in soil was investigated using soil columns (5 cm I.D. ${\times}$ 30 cm H.) parked with two soils of different physicochemical properties. $^{14}C$-Activities leached from the soil A (loam) columns with and without rice plants for 117 days were 0.42 and 0.54% of the originally applied, whereas those from the soil B (sandy loam) were 0.21 and 0.31%, respectively. $^{14}C$-Activities absorbed by rice plants from soil A and B were 3.87 and 2.79%, respectively, most of which remained in the root. Irrespective of soil types, more than 96% of the total $^{14}C$ resided in soil, mostly in the depth of $0{\sim}5$ cm. The water-extractable $^{14}C$ in soil was in the range of $6.10{\sim}9.01%$ of the total $^{14}C$ applied. The rest of $^{14}C$, which corresponds to non-extractable soil residues of [$^{14}C$]paraquat, was distributed in humic substances in the decreasing order of humin>humic acid>fulvic acid. The soil pH of the columns without rice plants increased after the leaching experiment due to the flooded anaerobic condition resulting in the reduction of the $H^{+}$ concentration, whereas that of the columns with rice plants did not increase by the offsetting effect of the acidic exudates from the roots. Low mobility of paraquat in soil strongly indicates that no contamination of ground water would be caused by paraquat residues in paddy soils under normal precipitation.

• Korean Journal of Soil Science and Fertilizer
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• v.9 no.1
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• pp.1-8
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• 1976

1. Under an asumption that Ficks diffusion equation could be applicable in soil systems, the diffusivities of NaCl in several flooded soil systems were measured to range from $0.4{\times}10^{-5}cm^2sec^{-1}$ to $0.83{\times}10^{-5}cm^2sec^{-1}$ 2. It was discussed that, when a polder soil with a uniform initial salt content through the profile is desalinated only by diffusion to flooding water, the salt content in profile is a function of soil depth, diffusion time, and diffusivity as following $$C=C^{\circ}erf\frac{x}{\sqrt[2]{Dt}}$$ 3. On the basis of Kirkham, et al's integration of complementary erra function, the speed of desalting was discussed to be inversely proportional to the square root of time as following $$dq/dt=C^{\circ}{\sqrt{D/{\pi}t}}$$ 4. It was estimated enough to exchange the flooding water once or twice, even when desalination of polder soil is carried out only by diffusion, if the desalination begins in June, the used flooding water is fresh water, and flooding depth is 10cm. 5. Desalination of polder soil by diffusion requires 2 month for good standing of planted rice.

• Korean Journal of Soil Science and Fertilizer
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• v.12 no.3
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• pp.117-124
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• 1979

The present work was carried out to study the fate of applied phosphorus labelled with $^{32}P$ and its availability to plants in soils subjected to different management practices. The results can be summarized as follows (Table 3): 1. The applied phosphorus was transformed into different phosphorus compounds in the soils depending upon the management practices and soil characteristics. 2. In the flooded paddy soil (pH 5.8) added P after one week of incubation was transformed into various fractions, the order of abundance being: Al-P> Ca-P$${\sim_\sim}$$Fe-P> Org.-P. After two weeks the order changed to: Fe-P> Al-P> Ca-P> Org.-P. The amounts of the Fe-P and Al-P fractions were found to increase from the second week of incubation whereas a decrease in Ca-P was noticed with the organic-P remaining constant. The amount of available P decreased from the first to the third week of incubation, but increased thereafter. 3. In the volcanic ash soil a major proportion of the applied phosphorus was found in the Fe-P fraction during the whole experimental period. The interconversions of the $^{32}P$ among the different phosphate fractions was not as evident as in the case of flooded rice soil. The recovery of applied P was low and remained constant throughout the incubation period. 4. In the upland soils relatively more of the applied phosphorus was found in the Ca-P fraction as compared with those of the other soils. As in the flooded paddy soil $^{32}P$ in the Ca-P fraction decreased with increasing incubation time, whereas in the Fe-P fraction it increased with time. The recovery of added phosphate as available P followed different patterns for the cultivated and the uncultivated soils. In the cultivated soils lit was relatively high and remained nearly constant during the whole incubation period. In the uncultivated soil on the other hand, it was high at the earlier time of incubation, but decreased with incubation time.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.44 no.3
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• pp.225-229
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• 1999

Unstable seedling stand establishment of wet direct seeding culture of rice is one of the major elements preventing the extension of its culture area. In order to develop methods of seedling stand improvement in direct seeded rice on flooded surfaces, three field experiments were conducted on silty loam soil using a cultivar 'Donjinbyeo' for three years, mainly focusing on water management after seeding and seed soaking with plant growth regulators (PGRs). Under the condition of shallow flooding after seeding, seedling stand rate increased and floating seedling rate decreased in both early and normal season seeding compared to deep flooding. With earlier draining time after seeding, there was a tendency towards preferential growth of the seminal root, increase of seedling stand and decrease of the floating seedling rate. Therefore the highest seedling numbers per unit area and the lowest floating seedling numbers were found upon drainage at 1 day after seeding (DAS), while a contrary tendency was shown upon conventional drainage at 7 DAS. Seed soaking with PGRs such as Metalaxyl or mixing of Metalaxyl with gibberellic acid (GA$_3$) significantly increased the seedling stand. In addition the effects of PGR treatment on seedling stand and the early growth of plants were greater under flooded conditions than under drained conditions after seeding, although draining of water after seeding improved the seedling establishment rate more when compared with the PGR treatment. These results suggest that draining management after seeding or maintaining of shallow flooding for a week is the most effective method to improve the seedling stand rate in wet direct seeding.

• Journal of Biosystems Engineering
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• v.28 no.5
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• pp.411-420
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• 2003

Physical and cultural properties were investigated on the rice-seed pellets made by the pelleting machine(Yu, 2003) as the changes with mixing ratios of soil to rice seed of 6 : 1, 7 : 1, and 8 : I, and rotating speeds of forming rolls of 7, 10, and 13 rpm. Average weight, average diameter, and average sphericity of the pellets were 1.70 g, 12.0 ㎜, and 99.1 ％, respectively. Average number of seeds per pellet was more than 3, and almost all pellets had more than 3 seeds in the cases of mixing ratios of 6 : 1, and 7 : 1 at the forming rolls' speed of 7 rpm. Gradual drying was needed because rapid drying caused cracks on surface of the pellets. Compression strength of the pellets dried in shady room was in the range of 132 ∼ 152 N, which was enough for handling. Comparing with the previous pellets(Park, 2002), average number of seeds per pellet, ratio of pellets including more than 3 seeds, and compression strength increased due to the effects of pressure feed of pellet materials, and improvements of the forming rolls. Emergence ratio of the pellets made at the mixing ratio of 6 : 1 and the forming rolls' speed of 7 rpm, was 100 % on dry paddy and was 97 % on flooded paddy surface. Good growth characteristics, and yield except number of seedling stand and ratio of missing plant were shown in planting of the pellets made at the mixing ratio of 7 : 1 and the forming rolls' speed of 7 rpm on flooded paddy surface field. Considering the cultural results, the mixing ratio of 6 : 1, and the forming rolls' speed of 7 rpm seems to be optimum operating condition for the improved pelleting machine.

• Applied Biological Chemistry
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• v.25 no.2
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• pp.93-98
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• 1982

Residues of Fujione (Fudiolan, fungicide) and Ortran (Acephate, insecticide) in Korean rice crop were studied. Also the persistencies of the pesticides in rice paddy soil were investigated in field and in laboratory. The residual levels of the pesticides in rice plant, straw, unpolished and polished rice were varied with the application rates of the pesticides. The residues of Fujione and Ortran in unpolished rice were $0.07{\sim}0.09ppm$ and $0.01{\sim}0.53ppm$, respectively. The half life of Fujione was 30 days under aerobic and 150 days under flooded condition in the laboratory system. Whereas in the paddy field it was about 100 days. In the case of Ortran it was $3{\sim}4$ days and $13{\sim}14$ days in aerobic and flooded condition, respectively in laboratory system.

• Journal of the Korean Association of Geographic Information Studies
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• v.12 no.4
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• pp.1-17
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• 2009

In recent years, most of flood damage is associated with the levee failure. The objective of this study is to predict flow depths, flood area, flooding time and flood damage through flood inundation analysis considering the overflow of levee and the characteristics of levee failure. The hydrological parameters were extracted from GIS data such as DEM, land cover and soil map to estimate levee failure discharge. In addition, the characteristics of flood wave propagation could be accurately predicted as flood inundation analysis was accomplished considering the affection of structure within protected lowland and hourly prediction of flooded areas and estimation of flood strength will be utilized as basic data for the flood defence and establishment of measure to reduce flood damage.

• Korean Journal of Agricultural Science
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• v.46 no.4
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• pp.857-868
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• 2019

A flooded rice field is one of the significant sources of anthropogenic methane (CH₄) with the intensity of the emissions dependent on management practices. Incorporation of rice straw, which is one of the organic amendments, induces the increase of methane emissions during the flooding season. In this study, we measured of methane emission according to applications of rice straw in different soil textures during a cultivation period in 2017 and 2018. The fallow treatments were non application of rice straw (NA), spring plowing after spring spreading of rice straw (SPSA), spring plowing after previous autumn spreading of rice straw (SPAA), and autumn plowing after previous autumn spreading of rice straw (APAA). The SPSA treatment emitted the highest total methane from loam soil in both 2017 (596.7 CH₄ kg ha^-1) and 2018 (795.4 CH₄ kg ha^-1). The same trend was observed in silt clay loam soil; the SPSA treatment still emitted the highest amount of methane in both 2017 (845.9 CH₄ kg ha^-1) and 2018 (1,071.7 CH₄ kg ha^-1). The lowest emission among the rice straw incorporated plots came from the APAA treatment for both soil texture types in all the seasons. The conversion factors of the SPAA were 0.79 and 0.65 from the loam and silt clay loam soils, respectively. Relatedly, the conversion factors of the APAA were 0.71 and 0.43 from the loam and silt clay loam soils, respectively. The above observations mean therefore that incorporation of rice straw early in the fallow reduces methane emissions in the main rice growing season.

• Proceedings of the Korean Society of Crop Science Conference
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• 2006.04a
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• pp.258-259
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• 2006

• Proceedings of the Korean Society of Crop Science Conference
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• 2006.04a
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• pp.260-261
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• 2006