• KOREAN JOURNAL OF CROP SCIENCE
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• v.66 no.4
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• pp.271-278
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• 2021

Azolla is a genus of small aquatic ferns native to Asia, Africa, and America. Azolla is potentially significant as a nitrogen source in agriculture, particularly in conjunction with rice (Oryza sativa L.) cultivation. In addition, Azolla may either control weeds or act as a weed depending on management; therefore, we aimed to determine the effect of Azolla incorporation on weed (e.g., Monochoria vaginalis, Rotala indica, Aeschynomene indica, and Cyperus amuricus) control and its other benefits during rice cultivation. The effects of Azolla on weed emergence were evaluated based on plot area coverage by the Azolla mat, which appears as a green sheet over water, and the rate of weed emergence in paddy field. Weed occurrence was investigated 40 days after Azolla inoculation. Soil samples from the experimental plots were collected following harvest in 2014-2015, and analyzed. Moreover, rice growth, yield, and grain quality were measured. Azolla suppressed weed growth by 72%. Azolla mat incorporation in rice fields suppressed weed growth by over 60%. In addition, Azolla promoted nitrogen fixation. Compared with nitrogen management using chemical fertilizers, Azolla incorporation showed the potential for various positive effects, including the improvement of soil fertility by increasing total nitrogen, and organic matter content. Rice grown with Azolla maintained its yield without additional herbicide treatment. Moreover, the palatability of cooked rice was better when grown with Azolla.

• Korean Journal of Weed Science
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• v.8 no.1
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• pp.64-70
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• 1988

An experiment was carried out to know the effects of paclobutrazol on the lodging related traits and yield of a japonia (Seomjinbyeo) and an indica (Samgangbyeo) rice variety grown at 3 N levels (10, 20, 30 kg/10a) and 3 N split rates [basal + top dressing 15 days after transplanting (DAT) : top dressing 25 days before heading (DBH) was 100 : 0, 80 : 20, and 60 : 40]. Paclobutrazol (3kg/10a of 0.6% G) was applied 15 DBH and lodging related traits were observed 3, 13, 23, and 33 days after heading (DAH). The results obtained summarized as follows. 1. Culm length was increased as N level increased, but decreased by application of paclobutrazol. Culm length was not affected by N split rates in both varieties. 2. Lodging was not occurred at all plots, but lodging index of Seomingbyeo was much greater than that of Samgangbyeo. In both varieties loding index increased up to 23 DAH due to an increase in fresh weight and a decrease in breaking strength and levelled off thereafter due to a decrease in both fresh weight and breaking strength. 3. Culm length of Seomjinbyeo and fresh weight of shoot and culm length of Samgangbyeo were positively correlated with lodging index, but breaking strength was not correlated with lodging index in both varieties during the most of ripening stages. Direct effect of culm length contributing to lodging index was positive and much greater than that of fresh weight and breaking strength in Seomjinbyeo, but in Samganbyeo direct effect of culm length and fresh weight was positive, but that of breaking strength was negative with similar magnitudes. 4. Yield in brown rice of Seomjinbyeo was not affected by N level, but split application of N increased yield. In contrast, yield of Samgangbyeo was increased as N level increased, but yield was not affected by N split rates. Paclobutrazol did not affect yield of rice in Seomjinbyeo, but decreased yield by 5.2% in Samgangbyeo due to a decrease in the number of spikelets per panicle.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.25 no.1
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• pp.77-86
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• 1980

Asking to change the cropping patterns to save the labor and capitals in paddy rice cultivation, the study was intended to know the weed problems under the various possible cultural systems; namely, direct seeding (in broadcast and row), machine transplanting and hand transplanting. Under the conditions as weedy check plots, paddy yields were significantly variated among cropping systems, and the functions of panicle No. and spikelet No. to the yield were neglected, among others. However, the yield and yield components were narrowed among cropping systems, and the function of spikelets number per area was comparatively improved to the others.

• Korean Journal of Weed Science
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• v.16 no.1
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• pp.14-20
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• 1996

Growth, nutrient uptake and photosynthesis as affected by submersion of shoot in pickerel weed (Monochoria vaginalis Presl.) were determined. The shoots of pickerel weeds in hydroponic culture were subjected to the submerged or emerged condition at 3- or 5-leaf stage for 8 or 10 days. Under submerged condition, growth in plant height was enhanced, but leaf number, leaf area, fresh and dry weight were reduced compared to those under the emerged condition. Similar responses in growth to submergence were obtained with the pickerel weeds rooted in the soil. Under submergence, chlorophyll content increased during the first 2 days, but thereafter remarkably decreased at 3-leaf stage and after the first 4 days at 5-leaf stage. Compared to the emerged condition, uptakes of $NH_4\;^+$-N, $NO_3\;^-$-N, $P_2O_5$ and $K^+$ were reduced, but uptakes of $Ca^{++}$ and $Mg^{++}$ increased under the submerged condition. Photosynthetic rate of shoot under water, measured by $CO_2$electrode, showed the maximum by 210 ${\mu}$moles $HCO_3\;^-$/g F.W. at the 8th day after submergence(DAS) at 3-leaf stage and 320 ${\mu}$moles $HCO_3\;^-$/g F. W. at 6 DAS at 5-leaf stage. These results indicate that pickerel weeds grow much better when the shoot is air-exposed and are less tolerable to submergence at 3 leaf-stage than at 5-leaf stage.

• Korean Journal of Weed Science
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• v.3 no.1
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• pp.23-28
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• 1983

To study ecological characteristics of Eleocharis kuroguwai occuring in Korea its propagules were collected from 6 locations from the northern part to the southern part of Korea (Chuncheon, Suweon, Iri, Jeonju, Gwangiu and Milyang) in 1981, cultured and replanted 3 times (May 20, June 5, June 20) in 1982. They flowered from August 5 to August 27 when they were planted on May 20, and from August 20 to August 27 when they were planted on Tune 20. Plant height, number of tillers and top fresh weight/$m^2$ were 50-90cm, 500-875, and 175-750g, respectively when they were planted on May 20, and 40-70cm, 250-625, 325-625g, respectively when they were planted on June 20. Number of tubers per plant were 0.98-1.98 when they were planted on May 20, and 1.81-2.87 when they were planted on June 20. Eleocharis kuroguwai from Chuncheon or Suweon was more open in plant type, shorter in plant height, narrower in diameter of pedicel and shorter in inflorescence than those from Iri, Jeonju or Gwangju. Each of the local collections may be regarded as different ecotype, based on the above differences in morphology and responses in growth and flowering to the planting dates. The results appear to imply that Eleocharis kuroguwai weeds occurring in various locations of Korea are different one another in competitive avility with rice crop.

• Korean Journal of Weed Science
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• v.13 no.2
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• pp.138-150
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• 1993

Experiments were carried out to understand how much do the environmental factors affect growth and tuber formation of arrowhead, Sagittaria trifolia L. The more the light transmittance decreased, the more the numbers of leaves and floral axes decreased. The dry matter weight of tops and the number and the fresh weight of formated tuber were significantly different between the light transmittance of more than 50% and that of less than 30% at the 5% level of DMRT. Plant height, number and width of leaves, and number of floral axis were affected by the Light spectra. And the degree of their effects on growth of arrowhead was different form the light spectrum. The natural light and the clear cellophane film were the most effective to increase the number and the fresh weight of formated tuber and the green spectrum was the least effective to do those. Plant height grown at 0-5cm water depth was shorter than that at 10-20cm water depth. The deeper the water depth was, the lower the leaves number was. The fresh weight and the number of arrowhead tuber were most produced at 0cm water depth and theose were least at 20cm water depth. The shoot growth and the tuber formation of arrowhead was much increased with increase of the application rate of fertilizer. The difference of the transplanted tuber size was not affected at the shoot growth, but tuber formation of arrowhead was increased with increase of the transplanted tuber size. From viewing the effect of temperature after rice heading, the shoot growth and the tuber formation at $35^{\circ}C$ were also higher than those at $25^{\circ}C$.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.39 no.3
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• pp.285-294
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• 1994

Dried top and root extracts of seven different weed species, fresh top and root extracts, and various concentrations of extract (0, 5, 10 and 15%, W/V) and residue rate (0.0, 0.25. 0.5, 0.75 and 1.0%) of velvetleaf (Abutilon theophrasti Medic.) were used to study their allelopathic effects on alfalfa in the laboratory and greenhouse. Top and root aqueous extracts of common lambsquarter (Chenopodium album L.), giant foxtail (Setaria faberii Herrm), redroot pig-weed (Amaranthus retroflexus L), velvetleaf, large crabgrass (Digitaria sanguinalis L), canada thistle (Cirsium arvense L.) and prostrate knotweed (Polygonium aviculare L.) significantly inhibited germination, seedling length, weight, and vigor in alfalfa. Top growth extracts of weeds exhibited greater allelopathic effects than root extracts. Alfalfa test species, WL-320, responded significantly different to the various weed species extracts in terms of allelopathic effect. The regression slopes of various top extracts showed significant variation with respect to germination percentage. Velvetleaf (b=3.69) extracts were the most inhibitory, while large crabgrass (b=2.39) extracts had the least allelopathic effect on alfalfa. When compared the activity of fresh velvetleaf extract to that of dry velvetleaf extract, dry extract was more inhibitory to alfalfa germination and seedling growth. Germination, seedling length and weight of alfalfa were inversely proportional to the concentration of dried velvetleaf extracts. Seedling emergence and survival percentage was inhibited by velvetleaf residue mixture treatment. Also, more of the toxic effects were observed from the dried top extracts, as compared to extracts from fresh top and root. These results demonstrate the allelopathic activity of different weed species extracts and suggest that weeds may affect crop growth and development due to the inhibitory effects of allelochemicals present in weed tissue.

• Korean Journal of Agricultural Science
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• v.33 no.2
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• pp.123-127
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• 2006

This study was carried out to compare growth and yield performance for soil conditions at the Maize Genetics and Breeding Lab. in Chungnam National University. The waxy hybrid corn in the drained soil of paddy field showed higher fresh yield per 10a and 100-kernel weight per plant than control. The average dry yield of drained and drainless soil were 804kg/10a and 498kg/10a compared with a control (751kg/10a), respectively. The waxy hybrid corn in the drained soil also had better good stand and stay green characteristics than drainless soil condition, and showed moderately resistance to water stress and weed. Vegetational feature of weeds was characterized as the prevalence of Acalypha auatralis, Echinochloa crus-galli, Persicaria hydrpopiper in drained paddy soil and Persicaria hydrpopiper, Acalypha auatralis, Echinochloa crus-galli in drainless paddy soil, and Echinochloa crus-galli, Acalypha auatralis in upland soil.

• Korean Journal of Weed Science
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• v.32 no.1
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• pp.35-43
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• 2012

The objective of this research was to confirm the difference in physiological responses to environmental stresses such as chilling, high temperature, NaCl, and chemical stress (paraquat) in Protox inhibitor resistant-transgenic rice (MX, PX, and AP37) and its non-transgenic counterpart (WT). Transgenic and non-transgenic rice plants were exposed to a chilling temperature of $5^{\circ}C$ for 1 day or a high temperature of $45^{\circ}C$ for 4 days and allowed to recover at $25^{\circ}C$ for 6 days after the chilling treatment or 8 days after the high temperature treatment. Leaf injury, shoot fresh weight, porphyrin biosynthesis substances, and chlorophyll content were investigated in transgenic and non-transgenic rice at 6 days after 0.5% and 1% NaCl treatments or at 5 days after 0~300 ${\mu}M$ paraquat treatments. No significant difference in leaf injury and shoot fresh weight were observed between transgenic and non-transgenic rice during chilling and recovery. Plant height and shoot fresh weight were also similar between transgenic and non-transgenic rice during the high temperature and recovery period (0~5 days). However, plant height and shoot fresh weight in transgenic rice line MX and PX were lower than in non-transgenic rice at 6 days for recovery. Leaf injury, chlorophyll, and Mg-Proto IX ME contents had no significant difference between transgenic rice and non-transgenic rice after NaCl treatment, but Proto IX content for AP37 and shoot fresh weight for PX and AP37 in 0.5% NaCl treatment were significantly reduced compared with non-transgenic rice. There was no difference in leaf injury and shoot fresh weight when comparing transgenic rice and non-transgenic rice after paraquat treatment. Although transgenic rice and non-transgenic rice showed a little difference at a particular measurement period in certain environmental stresses, there was generally no difference in physiological responses between transgenic rice and non-transgenic rice.

• The Korean Journal of Pesticide Science
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• v.4 no.4
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• pp.81-86
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• 2000

The objective was to develop herbicides for liquorice (Glycyrrhiza uralensis), one of most important ingredients of herbal medicine in Korea. Soil-applied herbicides, pendimethalin at 1,585 g a.i. $ha^{-1}$, simazine at 1,000 g a.i. $ha^{-1}$, alachlor at 5 g a.i. $ha^{-1}$, metolachlor at 1,600 g a.i. $ha^{-1}$, and ethalfluralin at 1,050 g a.i. $ha^{-1}$ provided greater control of hairy crabgrass and barnyardgrass (> 60%) but less control of Abutilon avicennae and Fagopyrum esculentum under growth chamber conditions. Of tested soil-applied herbicides, pendimethalin and simazine showed slight injury to liquorice (<17%). In the field experiment conducted in Chunchon, pendimethalin and simazine provided greater control of weeds: total fresh weight of weeds in control plots was 187 g $m^{-2}$, while those in both herbicides-treated plots were nil. Fresh weights of liquorice seedlings in pendimethalin- and simazine-applied plots, however, were not different from those in control plots. Foliar-applied herbicides, such as dicamba at 964 g a.i. $ha^{-1}$, 2,4-D at 280 g a.i. $ha^{-1}$, mecoprop at 2,500 g a.i. $ha^{-1}$, flazasulfuron at 75 g a.i. $ha^{-1}$, imazaquin at 800 g a.i. $ha^{-1}$, bentazon at 1,600 g a.i. $ha^{-1}$, and pyribenzoxim at 30 g a.i. $ha^{-1}$ reduced the growth of liquorice seedlings and provided moderate to total damage. Overall results show that pendimethalin and simazine appears to be effective herbicide candidates for liquorice.