• Korean Journal of Weed Science
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• v.9 no.2
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• pp.168-173
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• 1989

In the characteristics of intra-specific competition according to bulrush density, the intra-specific competition in plant height began at 5 and 15% per pot in mixed culture and bulrush monoculture, respectively. The intra-specific competition in the shoot began at 5 plants per pot in both mixed culture and bulrush monoculture. The competition in dry matter weight began at 15 plants per pot in monoculture, and at 10 plants in mixed culture. On the rice density, the plant height, and numbers of shoot and dry matter weight in rice were rapidly increased up to 2.6, and 2.5 plants per pot, respectively, And then the increments were slow, The critical intra-specific competition of bulrush with rice was 2.5 to 3 plants per pot in their traits of rice, and especially the number of shoots and dry matter weights per pot showed significant decrements. In the different transplanting time in rice, the plant heights in both rice and bulrush elongated longer in mixed culture than in monoculture. The plant height of bulrush became shorter but the height of rice longer with late transplanting. The ratio of shoot number in rice to the number in bulrush was about 1 : 3 in all plots, and shoot numbers became less by late transplanting. The dry matter weight in both species were decreased by late transplanting, and the decrements were more prominent in bulrush than in rice.

• Journal of The Korean Society of Grassland and Forage Science
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• v.18 no.1
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• pp.27-34
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• 1998

The present study elucidates of the effect of less water stress in different temperature condition on the emergence of forage grasses. Water condition was controlled to 30% and 60% by water content by wet soil. The mean temperature is conducted by $10^{\circ}C$ (out side) and $20^{\circ}C$ (glass house). The results are as follows: 1. Mean emergence time and emergence day after sowing of grasses were greatly influenced by water content of soil and temperature. It was suggested that temperature was very important for the light competition with weed in the early growth of grass. 2. Accumulatied emergence of grasses was nat afected by temperature, but it was sensitively affected by water content of soil.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.25 no.1
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• pp.87-91
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• 1980

The competitiveness of 7 soybean (Glycine max (L) Men.) cultivars to weeds were studied. The two soybean cultivars that showed the greatest competitiveness to weeds by maintaining their yields were Suweon 83 and Dongbuktae; whereas the least competive were Columbus and Harosoy.

• Korean Journal of Weed Science
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• v.5 no.1
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• pp.73-84
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• 1985

25 tank-mixed combinations between Haloxyfop-methyl at 0, 0.05, 0.1, 0.15 and 0.2 kg ae/ha and Acifluorfen at 0, 0.082, 0.163, 0.245 and 0.326 kg ai/ha were applicated at post-emergence on the late-season cropped soybean(Glycine max) fields predominated by grasses and assessed on the weeding efficacy. A most abundant weed species on the experimented fields were found at September (25 species). The broadleaved weed species and sedges were successively and proportionately emerged by the control rate of grass species. From the mono-treatment of each herbicide, Haloxyfop-methyl was recognized as a highly selective one between grasses and soybean, and Acifluorfen between broadleaf weeds and soybean, respectively. By combined application with both herbicides a synergistic weeding efficacy was detected on total weed species, however antagonistic or additive on each weed groups. Among other traits of soybean, stem dry weight was influenced by weed competitions during October, number of pods per plant during August and seed yields during whole periods. For most effective and reasonable weeding, no less than 0.4 kg ai/ha of each herbicides should be applicated in combinations.

• Korean Journal of Weed Science
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• v.6 no.1
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• pp.33-41
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• 1986

This experiment was conducted to determine the influence of weed competition in sesame and the periods for weed control. Competition periods (days), for which sesame was seeded under transparent polyethylene film at May 15, were 10, 15, 30, 45, 60, 75, 90, and full growth season of sesame. Weed control periods (days), for which sesame was seeded under black polyethylene film at June 15, were 10, 15, 30, 45, 60, and full growth season of sesame. Dominant weeds were Ponulaca oleracea, Digitaria sanguinalis, Acalypha australis, L. Cyperus arnuricus, Arenaria aesrphllifolia, Cardamine flexucosa, Mollugo Stricta and Digitaria eschaemum. The number of weeds was maximum at the 30 days after planting. Broad leaf weeds were dominant than grass weeds, and then decreased the total number of weeds by the reason of major decrease of broad leaf weeds. However, the weight of weeds increased continuously. No weeds appeared until the 15 days after planting and the weight of broad leaf weeds was heavier than that of grass weeds until 45 days after planting. However, grass weeds were heavier than broad leaf weeds after 60 days after planting. The hazards of weeds on the growth and development appeared seriously from the 60 to 75 days after planting, but main yield reduction appeared from 30 days after planting. Therefore once more hand weeding should be practiced within 30 days after planting to minimize yield decrease. Serious hazards by weed growing appeared by removing black PE film after 15 to 30 days after planting in growth characteristics and 30 days later in grain yield. Leaf growth showed maximum from 45 to 60 days after planting and then decreased as compared with the continuous increase of stem and root in optimum planting, transparent PE film mulch and hand weeding. Leaf growth didn't show reducing in PE film mulch and weedy check but total weight of weeds increased and growth of sesame decreased as compared to PE film mulch and hand weeding. Leaf, stem and root growth of sesame, and weed weight under black PE film mulch showed same tendancy and lower growth of sesame as compared with optimum planting, transparent PE film mulch. Correlation between sesame yield and weeds weight were r =$ -0.874^{**}$ in the optimum planting and r = $-0.712^{**}$ in the late planting, so that the more weeds increase, the lesser sesame yield.

• Korean Journal of Weed Science
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• v.3 no.2
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• pp.156-165
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• 1983

This experiment was conducted to find out the effect of competitive duration and density of Cyperus serotinus Rottb. on rice growth and yield. In plant height of both rice and flatsedge, the compacter density of flatsedge, the higher was plant height. Rice in the 50 days competition with flatsedge had shorter culm than in other competition plots at all density. The panicle number was affected during the tillering stage. The spikelet number per panicle was influenced from 25 days to 50 days after transplanting. Grain maturity ratio and 1,000 grain-weight didn't decrease under competition before 50 days after transplanting. The competition during the tillering stage to the young panicle initiation stage decreased significantly rice yield. The rice competed with low density of flat sedge showed small decrement of yield and its components. The period reaching to maximum stem number of flatsedge become shorter as flatsedge density increased. Number of flatsedge tubers competed with rice produced was 40.1, 16.8 and 11.4 times as much in 1: 1, 1:3 and 1:5 density ratio of rice to flatsedge, respectively. Flatsedge dry matter weight and rough rice yield had the relationship of Y = 601. 95-$0.67x^{**}$.

• Korean Journal of Weed Science
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• v.9 no.3
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• pp.177-182
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• 1989

The plant height, shoot numbers and dry matter weight in both bulrush and rice were increased by high level of nitrogen fertilizer and especially the dry matter weights in both species were sharply increased by high level of nitrogen fertilizer. The plant height, dry matter weight in rice, and shoot, and dry matter weight in bulrush were increased by high level of phosphorus fertilizer. The deficient symptom disappeared with change of low level into high level phosphorus in rice. The plant height, dry matter weight and shoot numbers in rice and bulrush were increased by high level of potassium fertilizer. In the inter-specific competition in bulrush according to various water levels, the plant heights in both species elongated longer with deep water levels, and the plant height and dry matter weight in bulrush were more sharply decreased than in rice by deep water levels. The shoot numbers and dry matter weight were critically dropped above 6-8 cm water level. In case of the shoot numbers for light source, in both species were more decreased in mixed culture than each monoculture. The exserted shoot length and weight in bulrush were larger than those in rice. The shaded shoot dry weight was more decreased in mixed culture than in each monoculture, and the decrement was larger in bulrush than in rice.

• Korean Journal of Weed Science
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• v.4 no.1
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• pp.26-38
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• 1984

To investigate the varietal differences of weed competitive functions under the four different seeding and transplanting methods, rice cultivars, Milyang 23 and Sadominori, were used with the seven weeding methods, namely, weedy check, weed-free, once weeding at 3, 6, 9, and 12 weeks and two times weeding at 3 and 9 weeks after seeding/transplanting, respectively. As a result, the proper and reasonable weeding stages and times by total and respective weed group were estimated. Also the constructive characteristics for yield formations were evaluated under the different competitive conditions as affected by various cropping patterns.

• Korean Journal of Weed Science
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• v.12 no.3
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• pp.261-270
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• 1992

Many herbicides that are applied at the soil before weed emergence inhibit plant growth soon after weed germination occurs. Plant growth has been known as an irreversible increase in size as a result of the processes of cell divison and cell enlargement. Herbicides can influence primary growth in which most new plant tissues emerges from meristmatic region by affecting either or both of these processes. Herbicides which have sites of action during interphase($G_1$, S, $G_2$) of cell cycle and cause a subsequent reduction in the observed frequency of mitotic figures can be classified as an inhibitor of mitotic entry. Those herbicides that affect the mitotic sequence(mitosis) by influencing the development of the spindle apparatus or by influencing new cell plate formation should be classified as causing disruption of the mitotic sequence. Sulfonylureas, imidazolinones, chloroacetamides and some others inhibit plant growth by inhibiting the entry of cell into mitosis. The carbamate herbicides asulam, carbetamide, chlorpropham and propham etc. reported to disrupt the mitotic sequence, especially affecting on spindle function, and the dinitroaniline herbicides trifluralin, nitralin, pendimethalin, dinitramine and oryzalin etc. reported to disrupt the mitotic sequence, particularly causing disappearence of microtubles from treated cells due to inhibition of polymerization process. An inhibition of cell enlargement can be made by membrane demage, metabolic changes within cells, or changes in processes necessary for cell yielding. Several herbicides such as diallate, triallate, alachlor, metolachlor and EPTC etc. reported to inhibit cell enlargement, while 2, 4-D has been known to disrupt cell enlargement. One potential danger inherent in the use of soil acting herbicides is that build-up of residues could occur from year to year. In practice, the sort of build-up that would be disastrous is unikely to occur for substances applied at the correct soil concentration. Crop injury caused by soil applied herbicides can be minimized by (1) following the guidance of safe use of herbicides, particularly correct dose at correct time in right crop, (2) by use of safeners which protect crops against injury without protecting any weed ; interactions between herbicides and safeners(antagonists) at target sites do occur probably from the following mechanisms (1) competition for binding site, (2) circumvention of the target site, and (3) compensation of target site, and another mechanism of safener action can be explained by enhancement of glutathione and glutathione related enzyme activity as shown in the protection of rice from pretilachlor injury by safener fenclorim, (3) development of herbicide resistant crops ; development of herbicide-resistant weed biotypes can be explained by either gene pool theory or selection theory which are two most accepted explanations, and on this basis it is likely to develop herbicide-resistant crops of commercial use. Carry-over problems do occur following repeated use of the same herbicide in an extended period of monocropping, and by errors in initial application which lead to accidental and irregular overdosing, and by climatic influence on rates of loss. These problems are usually related to the marked sensitivity of the particular crops to the specific herbicide residues, e.g. wheat/pronamide, barley/napropamid, sugarbeet/ chlorsulfuron, quinclorac/tomato. Relatively-short-residual product, succeeding culture of insensitive crop to specific herbicide, and greater reliance on postemergence herbicide treatments should be alternatives for farmer practices to prevent these problems.

• Korean Journal of Weed Science
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• v.1 no.1
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• pp.30-43
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• 1981

On unwedded paddy fields, six cropping patterns of rice cultivation, namely direct broadcast seeding, direct row seeding, machine transplanting, early season hand transplanting, standard season hand transplanting, and late season hand transplanting, were detected with two representative rice cultivars (Milyang 23 and Sadominori) to estimate the comparative fluctuation patterns of weed flora. As a result, number of emerged weed species, most crowding stages, differences of weed growth among cropping patterns, possible tendencies of competition in plant heights among plant groups, variations in Importance Values, and Simpson's Index analysis were discussed, respectively.