• Weed & Turfgrass Science
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• v.5 no.4
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• pp.219-224
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• 2016

This study was conducted to investigate the ecology of weed occurrence and to establish an economical paddy field weed control system for direct-seeded rice on water. The main problem weed among annual and perennial weeds was Eleocharis kuroguwai. The control effect of E. kuroguwai was low by the application of azimsulfuron + carfentrazone-ethyl + pyriminobac-methyl at the early stages of rice in directly seeded paddy fields, but most annual weeds including Echinochloa crus-galli were controlled. Also, the additional application of pyrazosulfuron-ethyl + thiobencarb GR at 20 days after first treatment or of bentazone SL at 43 days after the first treatment effectively controlled E. kuroguwai. Tuber formation of E. kuroguwai was inhibited by the additional application of pyrazosulfuron-ethyl + thiobencarb by 84%, but the dormancy rate of old tubers of E. kuroguwai under the soil was higher than that of E. kuroguwai tubers following single application of azimsulfuron + carfentrazone-ethyl + pyriminobac-methyl at the early stages of rice. Tuber formation was inhibited by the additional application of bentazone by approximately 87%, and the old tuber dormancy rate was low in the bentazone treatment. High amounts of old dormant tubers of E. kuroguwai were found in the weedy plots.

• Korean Journal of Environmental Agriculture
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• v.14 no.2
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• pp.221-231
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• 1995

The objectives of the present study were to find out the differences in growth and weed competition of rice under the foggy and non-foggy condition, and finally, the fundamental data for the establishment of the paddy weed control system under the locational foggy regions. The research was carried out on tin trays ($0.12m^2$) in greenhouse equipped with an Auto Foggy System(SAE KI RTN Co.). The results are summarized as follows: Exp. I. Difference in rice growth under the foggy and non-foggy condition. 1. While the plant height was not affected, the number of tillers was decreased by the foggy condition. The ratio of the number of effective tiller, however, became higher under the foggy condition. 2. Due to the fog present, the heading rate was decreased and heading time was delayed. 3. The foggy condition did not affect the dry weight of rice straw whether they were grown under the foggy or non-foggy condition. However, yield components such as the number of ears, the number of grains per ear, thousand kernel weight and percentage of ripeness were reduced. Particularly, weights of perfect brown and unpolished rice were also decreased. Exp. II. Effect of the duration of competition between weed and rice grown under the foggy condition on the growth of rice plant. 1. There was no difference in the height of rice grown under a different duration of competition. There was a clear tendency that the number of tillers of rice grown under the foggy condition was decreased as the duration of competition was decreased. 2. When the duration of competition was longer than 60 days, the heading rate was decreased and the initiation of heading was also delayed by 2-4 days. 3. Under the foggy condition, the duration of competition for more than 40 days affected dry weight of rice straw and the difference in yield was greatest in the non-competition and competition for more than 40 days.

• Korean Journal of Weed Science
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• v.30 no.1
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• pp.43-49
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• 2010

This study was conducted to predict the rice yield loss and determine the economic threshold levels for water direct seeded rice from competition of the most serious weeds, Scirpus juncoides Roxb. (bulrush) and Echinochlor crusgalli L. (barnyardgrass) in Daegu of Korea. To predict crop yield as a function of weed density used a rectangular hyperbola, and determine their economic threshold levels used the equation developed by Cousens. The rice yield loss model of S. juncoides was predicted as y = 466 / (1+0.00188x), $R^2$ = 0.933 and that of E. crusgalli was y = 458 / (1+0.02402x), $R^2$ = 0.973. In comparison of the competitiveness represented by parameter ${\beta}$, it was 0.001884 in S. juncoides and 0.02402 in E. crusgalli. Economic threshold calculated using Cousens' equation was negatively related to the competitiveness of weed. So that the economic threshold of S. juncoides was 13.4 and that of E. crusgalli was 1.07 plants per $m^2$.

• Korean Journal of Weed Science
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• v.32 no.3
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• pp.280-284
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• 2012

No-tillage direct seeding of rice is consumed less labor and oil energy by no plowing and rotary tillage. And it has other advantages of soil and water conservation and accumulation of organic matter on paddy surface due to crowded water foxtail (Alopecurus aequalis var. amurensis). When no-tillage seeding of rice, many water foxtail occurred in winter paddy field. In this experiment their covering degrees were 97.6% and 95.2% in clay loam and sandy loam paddy soils, respectively. Because of this, Stellaria alsine var. undulata, Cardamine flexuosa, Rorippa indica and Ixeris chinensis etc. annual and perennial wintering weeds occurrence was reduced. And annual weeds Chenopodium serotinum and Polygonum hydropiper that occurred early in spring were also reduced. As well as Echinochloa crusgalli var. praticola, Cyperus difformis, Monochoria vaginalis and Lindernia procumbens etc. summer annual weeds that occurred after irrigation were also reduced. In conclusion, no-tillage direct seeding of rice has another advantages of weed management by water foxtail.

• Korean Journal of Weed Science
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• v.18 no.3
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• pp.214-224
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• 1998

This study was conducted to develop labor and chemical cultural practice improvement for weed control in ginseng field. Five crop species were screened in vitro and three crop extracts were sprayed in the test allelopathic effect for weed species. Methyl alcohol extracts of rice, oat, rye and wheat straw showed inhibitory effect on the germination of six weed species, Amaranthus retroflexus, Chenopodium album, Arthraxon hispidus, Digitaria adscendens, Echinochloa crus-galli, and Setaria viridis. Especially, extract of oat straw was most effective to inhibit the germination of six weed species tested. Also, spraying the extract solution of rice, rye and wheat straw was effective to inhibit the growth of weeds in ginseng field. Ginseng root length, diameter, fresh and dry weight in extract spraying plot were higher than those of non-treatment plot.

• Korean Journal of Weed Science
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• v.18 no.4
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• pp.364-370
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• 1998

A weed population has been mainly analyzed through vegetative analysis method in ecology. However, this method is difficult to understand a detailed feature of weed dominance in terms of region and a particular weed species. Since GIS(Geographic Information System) tool has been introduced, this constraint was able to be solved. GIS analysis for the nationwide weed survey data in 1981 revealed that most predominant weed was Monochoria vaginalis and this species predominated mostly in a western part of Chungnam, a part of Kyunggi, a northern and southern part of Kyungbuk province of Korea. Eleocharis kuroguwai which was the most predominant weed species in 1992 was occurred at southern part of Kyunggi, central and western parts of Chungnam, and southern western part of Chumnam at the GIS analysis. GIS analysis was proven to give much more detailed information than vegetative analysis of weed population and this means that a data analysis by GIS would be used for operating a high effective control strategy against target weed species and site.

• Korean Journal of Environmental Agriculture
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• v.29 no.2
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• pp.109-114
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• 2010

Rape residue as green manure is an emerging alternative of chemical fertilizer to improve soil quality and crop productivity. Objective of this research was to evaluate the effectiveness of rape residue as green manure on reduction of chemical fertilizer and suppression of weed occurrence in rice-rape double cropping system. Greenhouse experiment was conducted with four treatments: the combination of rape residue and three different N application rates (0, 30 and 70% of recommended application rate (7.8 kg N $10a^{-1}$)) and 100% chemical fertilizer as a control. No difference in rice clum length was observed for all treatments, while panicle length was highest in a treatment of rape residue+70% chemical fertilizer (Rape+70%CF). In addition, rice grain weight at a Rape+70%CF treatment increased by 19% compared to the control. This treatment also reduced weed density and biomass by 58 and 53%, respectively, compared to the control. Our results suggest that use of rape residues as green manure is an environment friendly and effective way to reduce chemical fertilizer and to enhance crop productivity in rice-rape double cropping system in Korea.

• Korean Journal of Weed Science
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• v.31 no.3
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• pp.289-293
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• 2011

Field experiments were conducted to predict rice yield losses caused by Echinochloa crus-galli (L.)P. Beauv., Bidens frondosa L. and Aeschynomeme indica L. at a range of plant densities under machine transplanted rice cultivation in different regions of Korea in 2006, and to determine their economic threshold levels (ET). All data were fitted to Cousens' rectangular hyperbola to estimate parameters for predicting rice yield loss. The rice yield loss models of Bidens frondosa L. was predicted as y=5.43/(1+0.0113x), $R^2$=0.963, A. indica was y=5.47/(1+0.0332x), $R^2$=0.976 and E. crus-galli y=5.43/(1+0.01552x), $R^2$=0.950. The mean competitivities represented by the parameter, whose reciprocal ($1/{\beta}$) is a weed density reducing crop yield by 50%. Those of E. crus-galli, B. frondosa and A. indica were 0.01552, 0.01113 and 0.0332 in normal-season machine transplanting of Korea, respectively. Single year mean economic thresholds (ET) of A. indica were 0.5, 0.6 and 0.7 plant $m^{-2}$ with the application of flucetosulfuron, flucetosulfuron+imazosulfuron GR and flucetosulfuron+imazosulfuron+carfentrazone GR herbicides, respectively. Meanwhile ET values of 1.6, 1.9 and 1.9 plants $m^{-2}$ for B. frondosa, 1.2, 1.4, and 1.4 plants $m^{-2}$ for E. crus-galli.

• Korean Journal of Soil Science and Fertilizer
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• v.40 no.6
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• pp.495-500
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• 2007

Recently we are interest in organic farming of rice. The technology of paper mulching was practised without herbicide in machine transplanting cultivation of paddy. A field experiment was conducted in Gangseo series (coarse loamy, mixed, nonacid, mesic family of Aquic Fluventic Eutrochrepts) at the National Institute of Crop Science (NICS), RDA, Suwon, Gyeonggi province, Republic of Korea in 2004. This experiment was carried out to evaluate soil redox potential, weed control and rice growth by the different organic matter in paper mulching transplanting. Compost, rice straw and soiling rye were incorporated as organic matter. The nitrogen amount of controlled-release fertilizer (CRF) plot was 80% compared with nitrogen amount ($110kg\;ha^{-1}$) of conventional fertilization. Mulching paper consisted of recycled paper which was coated with biodegradable plastics. There were no difference between conventional rice transplanting and paper mulching on missing hills after organic matter application. Weed control were the highest at added soiling rye plot. The redox potential of soil was the lowest in rice straw + CRF 80% plot at tillering stage. The $NH_4{^+}-N$ in soil was the highest at soiling rye + CRF 80% tillering stage. There was no difference in yield between soiling rye + CRF 80%, compost + CRF 80% and conventional fertilization plot.

• Korean Journal of Weed Science
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• v.14 no.4
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• pp.258-264
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• 1994

The weed survey in lowland rice field in 1992 was conducted to identify weed population change as affected by different elevation, soil type and cultivation pattern at Gangweon province. There were more perennial weeds in plain and east coastal area while more annual weeds in mid alpine and alpine area. Meanwhile, perennial weed species was more dominant at ordinary and sandy soil but annual weed species was more dominant at poorly drained soil. In general, hand and machine(30 day old seedling) transplanting would result in higher dominant weed species of perennial while there was more annual weed species in machine (10 day old seedling) transplanting and dry seeding, respectively. Also, annual weed species was more predominant at spring plowing time compared to autumn plowing time. Particularly, there was change in dominant weed species with time. In 1971 annual weed species was more predominant but perennial weed species was highly dominant in 1981 and 1992.