• Journal of Biosystems Engineering
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• v.33 no.2
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• pp.83-93
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• 2008

In order to save labor and cost, direct seeding has been considered as an important alternative to the machine transplanting in rice cultivation. Current direct seeding machines for rice in Korea drill irregularly under various operating conditions. This study was conducted to develope a precision seeder which enables the accurate, even-spaced in row placement of rice seeds at uniform depths of 3-4 cm on dry paddy. Design, construction and performance evaluation of the precision seeder were carried out. The tractor rear-mounted type 8-rows precision seeder which performs seeding in addition to fertilizing, ditching, and rotary tilling works on dry paddy was developed. Main components of the seeder were ditcher and leveller, rotary tiller, powered roller type furrow opener, seeding device, powered roller type furrow covering and firming device, hydraulic unit, seeding speed control system, power transmission system, hitch and frame. Ditching, furrow opening, and seed covering and firming performances were good and seeding depths of 2-4 cm could be maintained. Planting accuracies and planting precisions were within 13.6%, and 31.2%, respectively, for planting space of 15 cm, and seeding velocity of 0.5 m/s. These mean variations of average planting space were within 2.1 cm, and 90% of seeds in a hill were seeded within 4.7 cm of hill length, respectively. Error ratios between setting planting space and measured average planting space were shown within 6.7%. Therefore the seeder showed good planting performance up to seeding velocity of 0.5 m/s in field tests. And field capacity of the seeder was about 0.28 ha/hour.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.20 no.2
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• pp.79-87
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• 2010

Objectives: The purpose of this study was to investigate the symptoms of work-related musculoskeletal disorders (WMSDs), the influence of the WMSDs on the health-related quality of life (HRQoL), and to identify the differences of WMSDs and HRQoL between greenhouse farmers and paddy farmers. Methods: Subjects were 34 greenhouse farmers and 56 paddy farmers who were living in a rural community. The sociodemographic characteristics, health-related behavior, working characteristics, WMSDs and HRQoL were investigated. WMSDs symptoms were measured by a selfassessed questionnaire on musculoskeletal disorders symptoms and HRQoL was measured by the Euro Quality of Life (Euroqol) EQ-5D index. The differences on the WMSDs, EQ-5D and it's related factors between the groups were assessed with t-test and ${\chi}^2$-test. Results: Greenhouse farmers were longer the working hours per day and working duration than paddy farmers. The level of prevalence of the WMSDs in greenhouse farmers is higher than in paddy farmers. The EQ-5D index of greenhouse farmers and paddy farmers were 0.819 and 0.874, respectively. Overall, the mean value of EQ-5D index was significantly lower greenhouse farmers than paddy farmers. Conclusions: These results showed that the HRQoL for farmers are strongly influenced by WMSDs and agicultural type in that we are aware of the need to comply with regulations of WMSDs, especially greenhouse farmers.

• Journal of People, Plants, and Environment
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• v.24 no.4
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• pp.389-401
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• 2021

Background and objective: The purpose of this study is to investigate the ecological status of six areas around Geumgang River that used to be farmlands before they were restored as a riverine ecobelt. This study aims to analyze the correlation between the location environment and ecological status of the sites to identify the environmental factors affecting them. Methods: The sites are classified into four types according to restoration: terraced paddy fields, flat paddy fields, artificial wetland, and landscape forest. The survey items were divided into land use status, plant ecology, and animal ecology. Results: In terms of plant ecology, terraced paddy fields showed favorable naturality with the rate of native species above 90% and the naturalization index below 10%. In terms of animal ecology, the total number of species found in these areas was biggest in terraced paddy fields, followed by flat paddy fields, artificial wetland, and landscape forest. Regarding species diversity, terraced paddy fields also showed abundant species with an average of 1.05 to 1.09. The results of the correlation analysis showed that the forest area around the sites had the most significant effect on species diversity. The grassland and open water area showed a positive correlation with the total number of animal species and the number of dragonflies, confirming that the marshy grassland had a positive effect. As the cultivated land and urbanized area around the sites increased, it had a negative effect on the distribution of native species and the number of animal species that appeared, and a positive effect on the naturalization index. Conclusion: It is necessary to establish preemption and restoration plans for sites such as grasslands adjacent to the forest and terraced paddy fields in order to promote resilience of the diverse species returning to the purchased lands.

• Korean Journal of Agricultural Science
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• v.47 no.2
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• pp.263-273
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• 2020

With the change of the agricultural environment (increased rice production, decreased rice consumption, and rice production policies), converting paddy fields into upland fields is an increasing trend. In terms of conversion into upland fields, subsurface drainage is one of the most important factors for good field crop growth. This study evaluates the performance of a subsurface drainage culvert system in paddy fields and reclaimed lands. The obtained results are briefly summarized as follows: 1) After a comparative evaluation of several subsurface drainage culvert systems, including excavated subsurface drainage and non-excavated subsurface drainage types, type 3 (non-excavated, perforated drain pipe 50 mm, filter mat B50 cm, subsoiling 70 cm and culvert spacing 5 m) shows relatively high values among four types in terms of effectiveness (subsurface discharge capability) and economic efficiency (construction cost). 2) Type 3 has proven that it is suitable for design standards of discharge capacity through field tests performed in paddy fields (three sites: Gong-geom, Gae-san, Juk-san) and reclaimed lands (two sites: Gum-ho, Mi-am). 3) In the experiment of Sesamum indicum growth according to the existence of a drainage system, Sesamum indicum growth with a subsurface drainage culvert system had good value in terms of plant shoot and root length, shoot fresh and dry weight, and root fresh and dry weight).

• Korean Journal of Environmental Biology
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• v.37 no.4
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• pp.690-706
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• 2019

Paddy fields play an important role in the biodiversity conservation of agroecosystems as man-made wetlands. This study focused on the floristic composition and characteristics of paddy fields in South Korea. The flora surveys were conducted in 33 areas in nine provinces at two times (June and August) in 2016. The results showed that the vascular plants of the paddy fields in South Korea included 389 taxa, composed of 51 families, 219 genera, 350 species, four subspecies, 30 varieties, and five forms. Among the 51 families, Gramineae was the most diverse in species (76 taxa), followed by Compositae (61 taxa), Leguminosae (32 taxa), Cyperaceae (27 taxa), Polygonaceae (15 taxa), and Scrophulariaceae (12 taxa). Based on the occurrence frequency of each species, Digitaria ciliaris (Retz.) Koel. (100%), and Echinochloa crus-galli (L.) P.Beauv. (100%) were the highest, followed by Acalypha australis L. (97.0%), Bidens frondosa L. (97.0%), Alopecurus aequalis Sobol. (97.0%), Rorippa palustris (Leyss.) Besser (93.9%), Ludwigia prostrata Roxb. (93.9%), Lemna perpusilla Torr. (93.9%), Mazus pumilus (Burm. f.) Steenis(90.9%), Rorippa palustris(Leyss.) Besser(87.9%), Eclipta prostrata(L.) L.(87.9%), Commelina communis L.(87.9%), Artemisia princeps Pamp.(84.8%), Erigeron annuus (L.) Pers.(84.8%), Cyperus microiria Steud.(84.8%), and Aneilema keisak(Hassk.) Hand.-Mazz. (81.8%). The biological type of paddy fields in South Korea was determined to be Th-R₅-D₄-t type. Rare plants were found in six taxa: Aristolochina contorta Bunge, Penthorum chinense Pursh, Sagittaria sagittifolia subsp. leucopetala (Miq.) Hartog, Ottelia alismoides (L.) Pers., Pseudoraphis ukishiba Ohwi, and Acorus calamus L. Eighty taxa contained naturalized plants composed of 15 families, 54 genera, 76 species, three varieties, and one form. The urbanization and naturalization indices were 24.8% and 20.6%, respectively.

• Journal of Biosystems Engineering
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• v.40 no.4
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• pp.305-313
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• 2015

Purpose: This study was performed to predict the fatigue life of a crank-type rotavator operated in domestic soil conditions using Recurdyn$^{(R)}$, a dynamic analysis program. Methods: Torque on the PTO shaft was measured using experiments conducted on the uplands and paddy fields in Korea. On the basis of the experimental and analytical results, the fatigue life of the crank-type rotavator was predicted by constructing an S-N curve according to the GL (Germanischer Lloyd Wind Energie GmbH) guideline. Results: The torques experienced by the PTO shaft in the paddy soil and the uplands were in the range of 472~797 N m and 313~430 N m, respectively, for every condition. In case of load condition, the peak torques (846 N m, 770 N m) were applied for severe conditions, resulting in a maximum (von Mises) stress of 75 MPa at the crank arm. The fatigue life of the crank-type rotavator was predicted to be 1,167 h that satisfies the target value of 1,110 h, by substituting the analysis results into an S-N curve of crank arm. Conclusions: The fatigue life of the crank-type rotavator was within the target life for the studied soil conditions; however, further field experiments for various soil conditions would be required to verify the prediction results.

• Korean Journal of Soil Science and Fertilizer
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• v.4 no.1
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• pp.87-94
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• 1971

• KOREAN JOURNAL OF CROP SCIENCE
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• v.30 no.3
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• pp.217-222
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• 1985

The yield responses of three isogenic lines in plant type of paddy rice(open-, spread- and broom-type) as affected by combined treatments of transplanting densities (47.62, 22.22, 15.15, 11.11 and 8.33 hills per sq. meter) and rates of fertilizer application (0, 0.5, 1.0 and 1.5 folds of standard rate) were studied by using of the partial differentiations by planting density(D):df(D,F)/dD, fertilizer rate(F):df(D,F)/dF, and their interaction(DXF):d$^2$ f(D,F)/dDdF from the multiple regression polynominal equations. Under the condition of wider planting, the broom-type showed most prominent and sensitive responses in yield among others. Also the action of transplanting density in the broom-type were positive both at lower and higher densities. Under the lower densities, the broom-type represented positive actions both at lower and higher rates of fertilizer application. Whereas the interactions between the density and fertilizer rate under the lower densities were rather negative. To achieve the labor-saving by lower transplanting density(11-14 hills per sq. meter), the amount of fertilizer rates were estimated as 1.3-1.5 folds much of the standard in the open-type, whereas more than 1.5 folds in the broom-type. Thus, the potentials to absorb more amounts of fertilizer may explain the compensating function of the broom-type for equivalent yields of the standards at reduced transplanting densities.

• Korean Journal of Environment and Ecology
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• v.26 no.3
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• pp.313-321
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• 2012

To analyze the bird communities by the land use type, we surveyed 43 plots in Siheung City, Korea from Mar. 2009 to Feb. 2010 and classified the community by TWINSPAN and DCA. Classification result by TWINSPAN was classified into 4 communities. In the first division, waterbirds, such as spot-billed duck(Anas poecilorhyncha) and great egret(Egretta alba) operated as the differential species. In the second and third division, little grebe(Tachybaptus ruficollis) and eurasian sparrow(Passer montanus) were operated as the differential species. The relationship between land use types and classified bird communities, all plots of community I were located in the forest. Community II plots were contained all urban and several semi-natural land use types. Community III contains stream and rice paddy. Plots in the reservoir were classified community IV. The stream and rice paddy were classified into different communities, which were colsely related with the size of wetland paddy. Community III had the highest species diversity index and community II had lowest. Community III also had the highest maximum species diversity index and evenness index. The result of this study, small stream and small rice paddy located within the city have insignificant characteristics as the habitat for birds. Management size of semi-natural land use for wildbird habitat in the urban area should be considered for showing their habitat characteristics. If the classification of biotope type based on the scale of rice paddy and urban park and the type of landuse type in the riverside then we should be consider the standard of minium area.

• Korean Journal of Soil Science and Fertilizer
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• v.10 no.1
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• pp.39-48
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• 1977

The results of the determination of the optimum level of nitrogen fertilizer experiment for rice paddy at 21 locations over the country in 1975 year are as follows. 1. The yields of control and N-fertilized plots of ordinary variety (Japonica type) were normal paddy soil>sandy paddy soil>poorly drained paddy soil. Control plots of Tongil variety, (Indica type) however, were sandy poorly drained soil>sandy normal paddy soil=clay poorly drained soil, and N-fertilized plots were normal paddy soil>sandy poorly drained soil>sandy soil>clay poorly drained soil. In other words Tongil variety has higher adaptability to sandy soil under no nitrogen. 2. The yield response to N-fertilizer was higher in normal paddy soil than sandy soil. The productivity per 1kg of nitrogen was 16.6kg in normal paddy soil, 10.5 in sandy soil, and 8.6-11.4 in poorly drained soil for Tongil variety. For ordinary variety, they were 12.6, 6.3, 6.6-9.3kg respectively. 3. Ripening ratio for ordinary variety and ripening ratio and grain weight for Togil variety were higher in sandy soil than normal paddy soil. The main reason why the N-response in mormal paddy soil is higher was appeared to be higher number of effective tillers in normal paddy soil. 4. The optimum rates of N-fertilizer in average were 19.4 in normal paddy soil, 14.6 in sandy soil, and 11.6-13.4kg/10a in poorly drained soil for Tongil variety. For ordinary variety they were 15.9, 10.2, and 8.7-12.7kg/10a respectively. 5. The optimum rate of nitrogen was increased with the increase of productivity in normal paddy soils. In sandy soils and poorly drained soils it was not proved. 6. The optimum rates of N-fertilizer calculated from field experiment were somewhat different from the optimum rates calculated from $SiO_2/OM$ ratio. However, the values calculated both ways showed high correlation. It would be recommendable, therefore, to use $SiO_2/OM$ ratio to calculate the optimum rates of N-fertilizer after revising this equation considering different rice varieties and soil types or water management and climate.