• Journal of the Korean Society of Environmental Restoration Technology
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• v.16 no.5
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• pp.19-26
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• 2013

This study was carried out to provide preliminary data for increasing biodiversity in agricultural ecosystem and investigate availability of using Tubificidae spp. for environment-friendly agriculture through the survey of growth of Tubificidae spp. in flooded paddy fields during winter. We estimated the number of Tubificidae spp. in rice paddy where had been flooded during the previous winter in Ganghwa-gun, Suwon-si, and Hwaseong-si (Bongdam-eup and Paltan-myeon) between March and April from 2010 to 2012. During growing period of rice, the number of Tubificidae spp. was compared between flooded and non-flooded paddy field in Ganghwa-gun. As results, mean density of Tubificidae spp. in winter flooded paddy field was 7,235.5 $ind./m^2$ in Ganghwa-gun, 14,347.5 $ind./m^2$ in Suwon-si, 59,989.9 $ind./m^2$ in Bongdam-eup, and 2,610.6 $ind./m^2$ in Paltan-myeon. Mean density of Tubificidae spp. was the highest in flooded paddy fields of Bongdam-eup that was kept wet until rice harvest time and had shallow water. While mean density was the lowest in Paltan-myeon where had deep water and later flooded paddy field than others. In Ganghwa-gun, during growing period of rice, mean density of Tubificidae spp. in flooded paddy fields (171,109.0 $ind./m^2$) and flooded fallow paddy fields (321,084.2 $ind./m^2$) was much higher than non-flooded paddy fields (1,006.6 $ind./m^2$). Flooded paddy field during winter can help increase the number of Tubificidae spp. which can control weeds and enhance biodiversity in paddy fields for environment-friendly agriculture. Early flooding and shallow water of paddy fields could be a good agriculture practice to encourage the growth of Tubificidae spp..

• Journal of Biosystems Engineering
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• v.27 no.2
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• pp.133-142
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• 2002

This is a fundamental study to develop a sensor to detect weeds in paddy field using machine vision adopted spectralphotometric technique in order to use the sensor to spread herbicide selectively. A set of spectral reflectance data was collected from dry and wet soil and leaves of rice and 6 kinds of weed to select desirable wavelengths to classify soil, rice and weeds. Stepwise variable selection method of discriminant analysis was applied to the data set and wavelengths of 680 and 802 m were selected to distinguish plants (including rice and weeds) from dry and wet soil, respectively. And wavelengths of 580 and 680 nm were selected to classify rice and weeds by the same method. Validity of the wavelengths to distinguish the plants from soil was tested by cross-validation test with built discriminant function to prove that all of soil and plants were classified correctly without any failure. Validity of the wavelengths for classification of rice and weeds was tested by the same method and the test resulted that 98% of rice and 83% of weeds were classified correctly. Feasibility of CCD color camera to detect weeds in paddy field was tested with the spectral reflectance data by the same statistical method as above. Central wavelengths of RGB frame of color camera were tried as tile effective wavelengths to distingush plants from soil and weeds from plants. The trial resulted that 100% and 94% of plants in dry soil and wet soil, respectively, were classified correctly by the central wavelength or R frame only, and 95% of rice and 85% of weeds were classified correctly by the central wavelengths of RGB frames. As a result, it was concluded that CCD color camera has good potential to be used to detect weeds in paddy field.

• Journal of Biosystems Engineering
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• v.26 no.3
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• pp.221-228
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• 2001

Chemical application, one of the most important crop management processes happened to cause spray drift, that would threaten farmers in field as well as dwellers in rural region. Spray drift was affected by micro-meteorological parameters. A study to evaluate short distance drift characteristics of a boom sprayer in paddy fields has been undergoing. This study is the first step of the research. Main purpose of the was conducted to develop a mean wind profile and to get information on turbulence intensities above and within rice canopy. Wind in rice paddy field were measured at every 10cm from 10 to 180cm above the ground using a 2-dimensional probe and a hot wire anemometer system. Main results were summarized as follows. 1. Mean wind profile was modeled as; Equations. see full-text 2. Roughness length and zero-displacement in rice canopy were analyzed to be respectively 0.04 and 0.7∼0.72 times of the canopy height. The values are smaller comparing to those of other crops because rice canopy is flexible and uniform comparing to other crops. 3. Turbulence intensities (Tl) was greater as close to the ground and became constant at heights greater than 1.5Hc. where Tl’s were 0.4 and 0.15 in horizontal and vertical direction respectively.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.60 no.3
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• pp.300-307
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• 2015

In order to develop optimum paddy-upland rotation system, we evaluated the 1st and the 2nd upland growth and yield characteristics of foxtail millet, proso millet, sorghum rotated from paddy field and rice rotated from upland in paddy-upland rotation. Average number of ears per hill was 3.3 in the 2nd upland cultivation. The value was greater by 1 ear as compared to 1st upland cultivation (2.2 ears per hill). In average yield per 10a, the 2nd upland cultivation showed 220.3 kg, 23% increased yield compared to the 1st upland cultivation (179 kg per 10a). In average number of ears per hill, the 2nd upland cultivation showed 8.3 ears, increased 4 ears compared to the 1st upland cultivation (4.2 ears per hill). In average yield per 10a, the 2nd upland cultivation showed 152.8 kg, 16.8% increased yield compared to the 1st upland cultivation (130.8 kg per 10a). In average days from seeding to heading of 5 sorghum varieties, there were no significant difference between the 1st (68.6 days) and the 2nd (67.4 days) upland cultivation rotated from paddy field. In the average number of grains per ears, the 2nd upland cultivation showed 2,931.6 grains per ear, 12% increased compared to the 1st upland cultivation (2,619.6 grains per ears). Average yield per 10a of sorghum in the 2nd upland cultivation showed 242.3 kg, 4.6% increased compared to the 1st upland cultivation (231.7 kg per 10a). In growth and yield characteristics of rice in paddy-upland rotation, culm length in paddy-upland-paddy plot showed 82.9 cm, 7.3 cm longer compared to the continuous rice paddy field (75.6 cm). Ear length was also 1 cm longer than that of the continuous rice paddy field. In average number of ears per hill, paddy-upland-paddy plot showed 25.0 ears, 4.3 ears more than that of the continuous rice paddy field (20.7 ears per hill). In average yield of rice per 10a, the paddy-upland-paddy rotation plot showed 526.8 kg, 9.8% higher yield compared to the continuous rice paddy field (479.9 kg per 10a).

• Journal of the Korean Society of Environmental Restoration Technology
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• v.14 no.1
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• pp.35-42
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• 2011

The current study analyzed appropriateness of abandoned rice paddy wetlands as habitats for the Amphibia by assessing functions and value of abandoned rice paddy wetlands within land development districts as a habitat for living creatures and researching into the Amphibia living in the subject districts. For this purpose, the study designated abandoned rice paddy wetlands within Hwaseong A District and Pangyo B District under land development as subject lands. Those wetlands went through succession after abandonment of farming. Detailed study results are as follows. From classification of wetland types and an analysis of their characteristics, it was found that herbaceous plants such as smartweed communities, horsetail communities and reed communities, and woody plants such as pussy willow communities appeared in both districts. These abandoned rice paddy wetlands shows typical characteristics of palustrine wetlands. As a result of a vegetation structure research, it was observed that succession has been progressed for at least over 2~3 years. In assessment of wetland functions by item, it was found that they are developing into fine wetlands in terms of functions because they are ranked over Moderate Class except separate distance from streams. Also from a research into animals living in the abandoned rice paddy wetlands, it was found that main inhabitants are Rana nigromaculata,Rana dybowskii, Hyla japonica, Bufo bufo gargarizans, etc. It can be confirmed that the abandoned rice paddy wetlands are providing appropriate conditions as habitats to the Amphibia in a view that those species have life cycles of inhabitation (shores and wetlands) - egg-laying (rice paddy, puddles and swampy places) - hibernation (rice field banks and swampy places). From this point of view, it was found that abandoned rice paddy wetlands that developed because of abandonment of farming can be used as means to improve structure and functions of habitats.

• Journal of Ecology and Environment
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• v.35 no.2
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• pp.149-155
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• 2012

Rice paddy fields have been recognized as an alternative habitat for avian wetland foragers, and fish-rice farms have become a new tool in improving the abundance of aquatic animals. However, the use of the habitats by avian foragers, particularly by oriental storks ($Ciconia$ $boyciana$), was not well understood. In the present study, we investigated how a fish-rice farm influenced the abundance of aquatic animals and documented the foraging behavior of the two captive bred oriental storks in a closed semi-natural paddy field. Our results showed that the fish refuge pond (water depth 40 cm) had a higher abundance of fish whereas the areas planted with rice (water depth 20 cm) had more tadpoles and some aquatic insects. The two captive bred oriental storks captured mostly fish and aquatic insects in the rice-planted area and mostly fish in the fish refuge pond. The two oriental storks had higher foraging success and spent more time for foraging in the rice-planted area than in the fish refuge pond. This result suggests that the oriental storks might prefer foraging in the area with fish, aquatic insects, and amphibians under a greater success rate presumably due to shallow water depth in the paddy fields with a fish-rice farm.

• Journal of Biosystems Engineering
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• v.31 no.3 s.116
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• pp.188-193
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• 2006

Elevation differences within a paddy field relate strongly to plant health, crop homogeneity, and pest control. For precision agriculture (PA), the elevation within a field should be precisely controlled. We analyzed variation in elevation within a rice paddy field over one crop cycle. The study took place in a rectangular plot (100 m x 30 m). Elevations within the a plots was measured by a laser-equipped surveying instrument, that could determine elevations to precisions of I mm. The test field was divided into grids with 30 squares; elevation was measured at the center of each 5 x 10-m grid square. This study measured elevation during nine observation periods from pre-plowing to post-harvest. Descriptive statistics showed the highest elevations after plowing due to soil disturbance. One-way analysis of variance (ANOVA) revealed significant elevation differences before and after plowing and transplanting, although elevations were similar over the period of crop growth. Comparison of pre-plowing and post-harvest data showed differences in elevations, indicating that elevation changes occurred during plowing, rice transplanting, plant growth, and harvesting. In summary, the above statistical analysis indicated that elevation changes occurred due to plowing but not during the plant growth season or due to harvesting.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.67 no.4
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• pp.326-334
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• 2022

This study was carried out to investigate the optimal nitrogen concentration level suitable for forage rice growth by hydroponic cultivation in the salinity concentration of 0.1~0.3% which is similar to that of Muan reclaimed paddy field, and based on this results, to estimate optimal nitrogen fertilization level by field experiment in Muan reclaimed paddy for maximum forage production by cultivation of Yeongwoo rice. As a result of the growth response to the salt and nitrogen concentrations in the hydroponic cultivation experiment, the growth amount increased as the nitrogen concentration increased in the range of 0~24 me/L in the absence of salt stress. However, at a salt concentration of 0.1~0.3%, the growth amount was the highest at a nitrogen concentration of 12 me/L, and at higher nitrogen concentrations of that, the rice growth decreased as the nitrogen concentration increased. Therefore, nitrogen concentration of 12 me/L was judged to be an appropriate concentration for forage rice growth at salt concentration of 0.1~0.3%, and a nitrogen fertilization amount level corresponding to a nitrogen concentration of 12 me/L was actually applied to the Muan reclaimed paddy field for forage rice cultivation during two years. The amount of nitrogen fertilizer was tested with three treatments, which are 18 kg/10a considered appropriate, and 1.5 times and 2 times of the appropriate amount, and the planting density was tested with 2 treatments of 15 hills/m² and 26 hills/m². As a result of the reclaimed paddy field experiment, the yield was the highest when nitrogen fertilizer was applied at 18 kg/10a in the planting density of both treatments. Looking at the yield according to planting density, the high planting density plot yielded higher than the low planting density plot. In other words, when the planting density was 26 hills/m² and the nitrogen fertilization amount was 18 kg/10, the highest dry matter yield of 1,763 kg/10a was obtained. From the results of hydroponics and reclaimed field experiments, we could conclude that the productivity of forage rice decreased more as the nitrogen concentration increased when the nitrogen concentration was higher than the optimal level under salt stress.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.47 no.2
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• pp.137-141
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• 2002

Decomposition of green manure is necessary for the nutrient supply in farm soil. Hairy vetch as a green manure is superior to other winter legumes in terms of wintering ability and N accumulation. This experiment was carried out to investigate the decomposition and N release of hairy vetch and its effect on rice production as the following crop in paddy field. Decomposition of hairy vetch placed by soil depth of 0, 10 and 20cm at transplanting time was investigated by mesh bag method, which was enclosed chopped residue in mesh bags. The fate of $^{15}$ N derived from $^{15}$ N-labeled hairy vetch was investigated at harvest in three levels of N fertilization. Grain yield of the transplanted paddy rice cultured with hairy vetch as starter N were compared with that of applying urea as starter N in the field. Hairy vetch residue decomposed very rapidly both in transplanted and dry-seeded paddy field. In transplanted paddy field, hairy vetch residue lost 72-81 % and 86-90% of its weight after one and five month, respectively, as affected by incorporation depth. The C/N ratio of the decomposing vetch residue increased sharply during the early stages and after then, decreased slowly. The amounts of N and P released from the vetch were about 90% and 97% of initial content after one month, respectively. Recoveries of hairy vetch-$^{15}$ N by rice plant were 30.6, 34.6 and 35.7% in 0, 6 and 12 kg urea-N 10 $a^{-l}$ application, respectively, indicating that N fertilization increased the recovery of hairy vetch. $^{15}$ N. Hairy vetch residue incorporated as starter maintained significant N $H_4$$^{+}$-N concentration in soil water of plow layer until effective tillering stage. Grain yield in the plot applied with hairy vetch was not significantly different from that in the plot with urea. We concluded that hairy vetch incorporation could substitute starter N fertilization and showed possibility to reduce N amount of top-dressing.g.g.

• Korean Journal of Agricultural and Forest Meteorology
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• v.18 no.4
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• pp.337-347
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• 2016

Carbon dioxide ($CO_2$) and methane ($CH_4$) were measured in a rice-barley double cropping and rice mono cropping paddy fields, which are located in the southwestern coast of Korea, over a one-year period. Net ecosystems $CO_2$ exchange (NEE) and ecosystem respiration (Re) were estimated by the eddy covariance (EC) method, and an automatic open/close chamber (AOCC) method was used to measure $CH_4$ fluxes. Environmental factors (solar radiation, air temperature, precipitation etc.) were also measured along with fluxes. After the quality control and gap-filling, the observed fluxes were analyzed. As a result, NEE was -603.0 and $-471.5g\;C\;m^{-2}\;yr^{-1}$ in rice-barley double cropping and rice mono cropping paddy field, respectively. $CH_4$ emissions increased during the course of flooded days and were similar in two cropping paddy field. Accoding to rough results considering only fluxes of $CO_2$ and $CH_4$, it was estimated that the carbon absorbation in rice-barley double cropping paddy field was higher than that in rice mono cropping paddy field by $128.9g\;C\;m^{-2}\;yr^{-1}$.