• Korean Journal of Environmental Agriculture
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• v.14 no.3
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• pp.296-301
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• 1995

For studying the role of acetone and surfactant in solution, and selecting the best surfactant for spray solution in herbicide screening, the solubilizability of 6 nonionic surfactant-acetone aqueous solutions to 18 herbicide technicals, their foliar wettability and phytotoxicity to soybean and rice plant were tested and evaluated. The solubilizability of surfactant-acetone aqueous solutions to herbicide technicals was dependent on the acetone content of solutions, and was less affected by nonionic surfactant. Foliar wettability of the surfactant solutions was good to soybean, but only polyoxyethylene lauryl ether HLB 13.6(LE-13.6) solution showed good wettability to rice plant within the concentration range of no phytotoxicity. Tween 20(0.1%), LE-13.6(0.01%) and polyoxyethylene nonylphenyl ether HLB 16.0(0.01%) solutions didn't induce phytotoxicity to soybean, and most of the surfactant solutions didn't induce phytotoxicity to rice plant. There was no surfactant that showed superior emulsifiability to various herbicide technicals, good foliar wettability to plants, and no phytotoxicity, but LE-13.6 was better than others.

• Korean Journal of Weed Science
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• v.15 no.1
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• pp.46-53
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• 1995

The herbicidal activity of thiocarbamate herbicides and its effect on cell division and elongation were determined. The herbicides studied were molinate(S-ethyl-N,N-hexamethylenethiocarbamate), dimepiperate [S-(${\alpha}$,${\alpha}$-di methylbenzyle)piperidine-1-carbothioate], esprocarb [S-benzyl-N-ethyl-N-(1,2-dimethylpropyl) thiocarbamate], and thiobencarb [S-(4-chlorobenzyl)-N, N-diethylthiocarbamate]. The herbicides applied at the rates ranged from $10^{-6}$ to $10^{-5}M$ did not affect germination and post-germination root growth of rice(Oryza sativa L.) and barnyardgrass [Echinochloa crus-galli(L.) P. Beauv.], but inhibited the post-germination shoot growth. There was no inhibition of gibberellin-induced ${\alpha}$-amylase biosynthesis in de-embryonated rice seeds by the herbicides at $10^{-5}M$, but about 50-60% inhibition occurred at $10^{-4}M$. When the herbicides were applied 7 days after seeding, the rates required to 50% growth inhibition of barnyardgrass were 146g, 91g, 96g, and 102g ai/10a for molinate, dimepiperate, esprocarb, and thiobencarb, respectively. No effect of the herbicides on cell division was found at $10^{-4}M$, but about 31 to 47% inhibition as compared with the untreated check was obtained by treatment of the herbicides at $10^{-3}M$. However, about 33 to 38% inhibition of cell elongation occurred at $10^{-5}M$ of the herbicides. They also inhibited IAA-induced cell elongation.

• Korean Journal of Organic Agriculture
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• v.25 no.2
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• pp.345-355
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• 2017

This study was conducted to evaluate rice seed disinfection efficacy of loess-sulfur for the suppression of Bakanae disease caused by Fusarium fujikuroi. Rice seeds were treated at different concentrations of loess-sulfur, soaking time and temperature, and combination of hot-water treatment. Rice cultivar, Shindongjin harvested from Bakanae disease-infested area in 2015, was used. Loess-sulfur was treated as follows; concentration of undiluted solution, 2%, 1% and 0.5%; soaking time of 24 and 48 hours; treatment temperature of $20^{\circ}C$ and $30^{\circ}C$; hot water treatment or not. Optimal conditions of rice seed disinfection were selected soaking time of 48 hours and the suspension of 0.5% and 1% loess-sulfur by investigating seed germination and isolation frequency of Fusarium spp. on Komada agar medium in vitro, and were established 3 disinfection conditions as hot water ($60^{\circ}C$, 10 min.) + 1% loess-sulfur ($20^{\circ}C$, 48 hours), 1% loess-sulfur only ($30^{\circ}C$, 48 hours) and 1% loess-sulfur only ($20^{\circ}C$, 48 hours) through additional test in greenhouse. Above 3 conditions were verified by rice seedling box and paddy field test in the way of investigating Bakanae diseased plants (%) and healthy plants (%). Consequently, most effective rice seed disinfection conditions on Bakanae disease were combination of hot water and 1% loess-sulfur and loess-sulfur only at $30^{\circ}C$. Furthermore, treatments with these conditions showed control value of 100% were maintained from seedling to the heading stage in the field. However, treatment of 1% loess-sulfur only at $20^{\circ}C$ showed low control value of 78.2% in paddy field. Hot water only treatment turned out to be an effective disinfection method when conducted thoroughly with $60^{\circ}C$, 10 min. However, it was thought additional soaking process with loess-sulfur after hot water treatment served more high control effect against Bakanae disease when rice seeds were disinfected on a large scale. This results expected rice seed disinfection with loess-sulfur were effectively and easily usable method if farmers had only one of either hot water-disinfector or seed-disinfector. In addition, loess-sulfur is well-known to farmers, simple to manufacture method and cheap.

• Korean Journal of Environmental Agriculture
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• v.18 no.3
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• pp.196-203
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• 1999

To establish the best rice cultivating system in the aspects of environment-loving agriculture, the amounts and patterns of nitrogen leached in the paddy soil were investigated with 7 treatments; Recommendation(R), Farmer's usual practice(FUP), Straw compost+chemical fertilizers reduced(SCF), Fresh straw+recommendation(FSC), Fresh cow manure(FCM), Cow manure compost(CMC), and no fertilization as Control(C). And SCF, FCM and CMC were applied with same amounts of total nitrogen to R. The infiltrated water samples were collected in ceramic porous cups which were buried at 60cm depth from the top. Concentrations of nitrate-N in irrigated water were $1.3mg\;l^{-1}$ on rice transplanting season when nutrients began to elute from paddy soil, and $0.4mg\;l^{-1}$ after breaking off irrigation. But it was $4-6mg\;l^{-1}$ in rice growing period. The maximum concentration of nitrate-N in leachate was not more than $7mg\;l^{-1}$ during rice cultivation. The amounts of nitrogen leached in R, FUP, SCF, FSR, FCM, CMC and C were 59, 63, 25, 41, 24, 27, $17kg\;ha^{-1}y^{-1}$ respectively. Nitrogen leaching was decreased to about 30% by supplement of fresh rice straw(FSC) to R. Furthermore, it was possible to reduce to over 50% of nitrogen leaching by reducing chemical fertilizer application(CF), or by substituting of chemical fertilizers with fresh cow manure(FCM) or cow manure compost(CMC). In added organic fertilizer treatments, the amounts of infiltrated nitrogen were less $13-46kg\;ha^{-1}y^{-1}$ than that of input by irrigation. This experiment showed that nutrients leaching was minimized by substitution of chemical fertilizers with organic fertilizer or by application of straw with chemical fertilizers in rice paddy soil and rice cultivation with suitable fertilizer management can work as a purifier rather than contaminator of water.

• Korean Journal of Environmental Agriculture
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• v.31 no.4
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• pp.293-299
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• 2012

BACKGROUND: Soil utilization pattern can be the main factor affecting soil physico-chemical properties, especially in soil phosphorus (P). Understanding the distribution and bioavailability of P is important for developing management to minimize P release from arable soils to environment. This study was conducted to evaluate the potential bioavailability of soil organic P by using phosphatase hydrolysis method. METHODS AND RESULTS: Twenty-four soils from onion-rice double cropping and 30 soils from plastic film house were selected from Changyeong and Daegok in Gyeongnam province, respectively. The P accumulation pattern (total P, inorganic P, organic P, residual P) and water soluble P were characterized. Commercial phosphatase enzymes were used to classify water-extractable molybdate unreactive P from arable soils into compounds that could be hydrolysed by (i) alkaline phosphomonoesterase (comprising labile orthophosphate monoesters), (ii) a combination of alkaline phosphomonoesterase and phosphodiesterase (comprising labile orthophosphate monoesters and diesters), and (iii) phytase (including inositol hexakisphosphate). Available P was highly accumulated with 616 and 1,208 mg/kg in double cropping system and plastic film house, respectively. Dissolved reactive P (DRP) and dissolved unreactive P (DUP) had similar trends with available P, showing 24 and 109 mg/kg in double cropping and 37 and 159 mg/kg in plastic film house, respectively, indicating that important role of dissolved organic P in the environments had been underestimated. From the result of phosphatase hydrolysis, about 39% and 66% of DUP was evaluated as bioavailable in double cropping and plastic film house, respectively. CONCLUSION(S): Orthophosphate monoester and orthophosphate diester accounted for high portion of dissolved organic P in arable soils, indicating that these organic P forms give important impacts on bioavailability of P released from P accumulated soils.

• Korean Journal of Weed Science
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• v.7 no.1
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• pp.90-97
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• 1987

An attempt was done at the Yeongnam Crop Experiment Station in 1986-'87 to obtain herbicide tolerant variant through cell culture. Immatured rice grain was more rapidly and efficiently formed callus in dehulled rice culture method for both rice cultivar types, Tongil type (Indica/Japonica) and Japonica-type. However, Japonica-type cultivar was generally superior than Tongil-type Cultivar in callus formation. Expression rate of herbicide tolerant variant varied depending upon rice cultivar, plant species and herbicide properties. In case of Nagdongbyeo (Japonica) at the first subculture, 46.3% of total callus pieces appeared as herbicide tolerant variant in herbicide media of CGA142464 and followed by NC-311 (11.6%), Butachlor (7.5%), 2.4-D (2.1%), Quinclorac (0.89%), and Propanil (0.25%), in order. This degree of appearance of herbicide tolerant variants rapidly increased as passage of subculture was advanced. Herbicide tolerant callus hardly regenerated as normal plant even though large variations exhibited among culture media.

• Korean Journal of Environmental Agriculture
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• v.30 no.3
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• pp.275-280
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• 2011

BACKGROUND: The present study was conducted to find out the suitable method for organic rice production on the basis of different seedling raising methods at nine eco-friendly agricultural units of Samgi, Mangsung, Iksan and Sungsan, Gusan of Jeollabuk-do, during 2009-10. METHODS AND RESULTS: On the basis of yield and physiological parameters, pot seeding method was found to be superior to drill seeding and broadcast seeding methods. The number of panicle, grain, the precent of ripened grains, and the 1,000 grain weight, were better in pot seeding method. Maximum yield and other attributes were recorded in rice, cultivated with seedlings raised by pot and broadcast seeding method. Number of panicle/hill and grain/panicle was 10.4% and 35.1% higher than the broadcast seeding method, respectively. Yield also showed 8.8% increase in pot seeding method as compare to broadcast seeding method. Higher grain yield was obtained when 56 hills/$3.3m^2$ of rice seedlings were used as compare to 50 hills/$3.3m^2$ raised by pot seeding method and 70 hills/$3.3m^2$ of broadcast seeding method. Lodging was minimum in seedlings raised with pot seeding method as thickness of third internode was more (9.0%) than the seedlings, raised with broadcast seeding method. Root length and dry weight also showed similar tendency i.e. 13.8% and 25.3% higher, respectively. CONCLUSION(s): Quality and grade of rice, cultivated with pot seeding method was better than broadcast seeding method. Head rice was 4.4% higher; and protein content and broken rice grown by pot seeding method were 0.4% and 1.8% lower than broadcast seeding method, respectively.

• Korean Journal of Environmental Agriculture
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• v.25 no.1
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• pp.58-63
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• 2006

In order to elucidate the adsorption and leaching characteristics of the insecticide imidacloprid in two types of paddy soils near Suwon, this experiment was carried out with $[^{14}C]$imidacloprid as a radiotracer. In an adsorption study conducted using $[^{14}C]$imidacloprid in 2 test soils, the adsorption coefficient was higher in soil A $(K_f\;2.6)$ than that in soil B $(K_f\;1.7)$. As calculated from Freundlich constant, distribution coefficients and half lives in soils, GUS indices showed low leachabilities of imidacloprid treated on the paddy soils into the groundwater. The amount of imidacloprid leached from the soil columns during the 4 weeks of leaching was less than 2% of the originally treated $^{14}C$. In the leaching test the amounts of $^{14}C$ activities distributed in the soil layer of 0-10 cm were more than 80% of the originally tented $^{14}C$ and those in rice plants were less than 3% of the originally treated $^{14}C$, suggesting that imidacloprid has very low teachability and bioavailability.

• Korean Journal of Environmental Agriculture
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• v.2 no.2
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• pp.108-113
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• 1983

There has been two kind of research fields in evaluating the ecotoxicity of chemicals The one is a bioassay and the other is an ecosystem analysis. The toxicants are transported into different biota, which have quite different environmental behaviour patterns and toxic properties. The effects of pesticides (butachlor, carbofuran, and tricyclazole) on periphyton community was studied by analyzing content of chlorophyll-a and autotrophic index (AI) that is a means of determining the trophic nature of the periphyton community. Results indicated that the content of chlorophyll-a was not influenced by the pesticides. The growth of algae was inhibited by sunshine period. And AI value is 43-2027: the large value indicates heterotrophic periphyton community, and was not affected by pesticides.

• Journal of Wetlands Research
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• v.20 no.2
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• pp.161-172
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• 2018

A mixed farming system that includes organic rice production and freshwater fish farming is being called into attention in Korean agricultural industry and rural areas in order to improve farm management and environmental conservation. This study was conducted to evaluate the environmental and ecological value of such mixed farming practices. Expert assessment and rapid assessment method (RAM) of wetland evaluation were employed for this study. Experts have responded that biodiversity conservation including amphibian and reptile habitat (2.39), aquatic insect habitat (2.36), Fishery habitat (2.34), vegetation diversity (2.13), avian habitat (2.05), and experience and education were the most important function of mixed farming. The wetland function evaluation conducted using modified RAM indicated that rice-fish mixed system showed improvements in most of the evaluated functions, compared to the conventional rice paddies. The overall wetland function of rice paddies in rice-fish mixed system was greatly improved as compared with the conventional rice paddies. Rice paddies are known to play an important role in biodiversity maintenance, and provide ecosystem services such as climate modulation and carbon reduction. Rice-fish mixed system of farming may not only improve various ecosystem services of rice paddies, but may increase farm income through value added fish farming, as well as promotion of social services such as education and maintenance of tradition. Additional research is needed for quantitative analysis of the values gained from the most improved wetland function when mixed farming system is actually put into practice, and to utilize the results in advertising of the organic rice, and in various sectors such as food, education and direct payment policy.