• Korean Journal of Weed Science
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• v.5 no.1
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• pp.50-55
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• 1985

Effects of weed removal time on maize growth and yield were evaluated in the fields dominated with Poligonum spp., Chenopodium album, Echinochloa crusgalli and Digitaria adsendens from 1982 to 1983 in Suweon. Weed removal treatments were as follows: (a) kept weedfree all season, (b) weeded at 10 day intervals after maize emergence but stopped weeding at 3,5,7,9 leaf stages, (c) weeds initially removed at 3,5,7 and 9 leaf stages and the plots then kept weed free, (d) weeds left all season. Maize kept weed free from maize emergence to 7 leaf stages showed no grain yield reduction due to competition from weeds emerging later, but weeding from emergence to 3 and 5 leaf stages reduced grain yield 46 and 44%, respectively, in 1982 and 29 and 18%, respectively, in 1983. Weeding at 3 leaf stage and thereafter did not influence grain yield but initial weedings at 5, 7 and 9 leaf stages reduced grain yield 10, 36, and 67%, respectively, in 1982 and 14,18, and 21%, respectively, in 1983. Responses of maize to weeding time in the dry matter yields were same as in the grain yields.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.52 no.3
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• pp.249-258
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• 2007

Experiments were conducted with aims to (1) estimate the biomass yield potential, (2) characterize the biomass and digestible dry matter production, and (3) reveal the characteristic seedling establishment of a whole crop rice variety, Nogyangbyeo, in dry- and wet-seeded rice. Maximum aboveground total biomass of Nogyangbyeo was 18 t $ha^{-1}$ in dry-seeded rice and 20 t $ha^{-1}$ in wet-seeded rice. Biomass yield potential of Nogyangbyeo was lower than that of Dasanbyeo. Comparatively, Nogyangbyeo was straw-dependent and Dasanbyeo was grain-dependent for biomass accumulation. Percentage of digestible dry matter (DDM) was higher in panicles than straw. Digestible dry matter yield was determined mainly by biomass yield rather than DDM percentage. Number of seedling establishment in Nogyangbyeo was $73m^{-2}$ in dry-seeded rice and $109m^{-2}$ in wet-seeded rice. Poor seedling establishment of dry-seeded Nogyangbyeo in the field condition was the result of low seed germination under low temperature and poor seedling emergence by deep sowing. Low seedling emergence rate of Nogyangbyeo was attributed mainly to slow elongation growth by slow leaf development and partly to mesocotyl and 1st internode lengths, not to genetically defined leaf length. The slow elongation growth of Nogyangbyeo was the same even in the high daily mean temperature of $24^{\circ}C$. Results suggest DDM yield in rice can be improved simply by increasing biomass and whole crop rice varieties should be adaptable to direct-seeding.

• Korean Journal of Agricultural and Forest Meteorology
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• v.7 no.4
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• pp.258-264
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• 2005

The objectives of this study were to study 1) emergence of pine bark beetles, 2) larval density in residual timber on Idlest land by each felling season, and 3) the secondary damage rates in the tended forest. Pine forest land which had undergone tending had a higher secondary damage ratio $(59.6\%)$ by pine bark beetles than forest land that was not tended $(2.8\%)$. The number of escape holes averaged 11.3 0.31 per $250 cm^2$ on the bark of leaf trees in the tended forest. The number of escape holes was higher in the Jinju site than in the Hamyang site. The larval habitat density of pine bark beetles as compared with each felling period was higher after mid-October than in forests tended early in October. Thus, forests should be tended before early October in order to prevent secondary damage from pine bark beetles. Secondary damage in the tended forest was higher in the upper part $(75.5\%)$ of the tree crown than in the lower part $(49.2\%)$. The damage was higher in terminal shoots $(80\%)$ than in lateral shoots $(48\%)$. Therefore, secondary damage by pine bark beetles can cause deterioration of the elongation growth of the forest trees. In conclusion, if by-products of tended pine forest forests are neglected, they will be utilized as a propagation site for pine bark beetles (Blastophagus piniperda L). The propagated adults will damage the tender shoots of the leaf trees and thus seriously limittheir elongation.

• Korean Journal of Weed Science
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• v.6 no.2
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• pp.124-129
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• 1986

Weeds emerging on winter wheat and barley field at early spring are troublesome, even with pre-emergence application of herbicides such as butachlor, tribunil, etc. Searching the proper post-applicating herbicides to control those weeds, three herbicides; ioxynil, bromoxynil and MCPA were evaluated with weeding efficacies in barley field. Tank mixture of bromoxynil and MCPA was the most excellent in weeding efficacy, especially in higher mixing rate at early April application to the broad-leaf weeds, among others.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.26 no.2
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• pp.185-191
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• 1981

The purpose of this paper is to define and describe a series of growth stages for maize. cv. MTC-l (early) and Suweon No. 19 (late) that are easily identifiable by both professional agronomists and farmers. Plants were grown at a density of 60cm row with plant spacing of 15cm at six different seeding times in 1980. Leaf development indices with ten grades (LDI) were identified and defined in accordance with the development of a leaf blade. Leaf appearance rate (LAR) was ca. 3 days and it was not influenced by the variety or seeding time. The elongation of the first internode above the ground level began in a month after emergence and it corresponded to the 8th or 9th leaf stage. Internodes elongated in regular sequence of node position. The morphological change of silks related closely with the development of kernel. The duration of generative development was not influenced by varieties and seeding time but that of vegetative growth was influenced. A new scheme for the maize which was made by the developed leaves, visible nodes above ground level, morphological change of silks and development of kernel was proposed.

• Journal of Radiation Industry
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• v.8 no.2
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• pp.111-121
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• 2014

This study was aimed to select useful mutants of rapeseed (Brassica napus L.) and leaf mustard (Brassica juncea L.), the seeds of three lines S-14, S-27, and S-28 were treated with gamma-ray and EMS. The optimum ranges of gamma-ray dose and EMS concentration to enlarge the characteristic morphological variations were also separately investigated. The survival rates of S-28 only linearly decreased with increasing the gamma-ray dose. The overall growth parameters decreased of gamma-ray dose in all three lines of S-14, S-27, and S-28. The reduction dosage 50 of gamma-ray was identified as 1,200 Gy for S-14 leaf mustard, while those of S-27 and S-28 rapeseed lines were appeared as same 1,000 Gy. The emergence rates of S-14 and S-27 showed no significant differences by EMS treatment, while the growth of all three lines were significantly decreased. The reduction concentration 50 in S-14 could not be determined, demonstrating that this leaf mustard line is presumably insensitive to mutagenic EMS, while those in S-27 and S-28 were identified as 3.0 and 2.5%, respectively, showing that these rapeseed lines possess higher sensitivity to EMS than S-14. Various morphological characteristics of $M_1$ generation obtained from mutagen treatment were elaborately investigated for further maintenance of $M_2$ generation. In $M_2$ generation variants showing short stem, yellow color in seed coat, chlorophyll deficiencies in leaf or pod, abnormal flower color were selected as potentially useful mutants for breeding.

• Korean journal of applied entomology
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• v.52 no.4
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• pp.431-436
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• 2013

Ricania sp. lay eggs into the new twigs of blueberry and suck nutrients causing growth retardation and a sooty mold symptom. This study was conducted to investigate the emergence success and developmental period of overwintered eggs of Ricania sp. under the seven constant temperatures from 10 to $34^{\circ}C$ by $4^{\circ}C$ intervals (14L:10D). We also monitored the emergence time of the Ricania sp. nymph at blueberry by 3 ~ 4 day interval using a modified leaf clip cage. Development times from the overwintered egg to $1^{st}$ nymph were 107.1, 54.5, 33.9, 25.3, 25.1 and 16.7 days and the emergence successes were 23.1, 30.8, 13.8, 21.7, 11.9, and 0.6% at 14, 18, 22, 26, 30 and $34^{\circ}C$, respectively except at $10^{\circ}C$. The developmental periods were decreased with increasing temperatures. First emergence date of the nymphs in the field was between 19 and 22 May, and the average emergence success was 19.6%. The present study might be helpful to establish the management strategy of Ricania sp. based on the biological characteristic.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.37 no.6
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• pp.534-540
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• 1992

Climatic condition and seeding depth affect the seedling stand and early growth in the direct-seeded rice cultivation on dry soil. This experiment was conducted to elucidate the effects of the day /night temperatures and the seeding depths on the seedling emergence and mesocotyl elongation of rice seed. Three combinations of the day/night temperatures(25/2$0^{\circ}C$ 20/15$^{\circ}C$ and 20/1$0^{\circ}C$) were employed with seeding depths 1, 3, 5 and 7cm at the Phytotron of the Crop Experiment Station in 1991. It appeared that seedling emergence ratio increased and days to seedling emergence decreased in the high temperature (25/2$0^{\circ}C$) and the deep seeding depth (5 and 7cm) condition. The seedling emergence ratio did not. show the, difference up . to the seeding depths of 3cm and below, but the ratio decreased from the seeding depths of 5cm and above. Plant height and leaf number were almost the same up to the depths of 3cm at 30 days after seeding, but those of the seeding depths of 5cm and 7cm were remarkably reduced in all temperature combinations. Mesocotyl and lower internode elongation were seen in the high temperature(25/2$0^{\circ}C$) with the seeding depths of 5cm and 7cm. In the seeding depth of 6cm, of the tested varieties, Tamjinbyeo and Odaebyeo showed the highest emergence ratio. Generally, leaves of all tested varieties appeared approximately in the soil depth of 3cm, so the reasonable seeding depth will be around 3cm in the direct-seeded cultivation on dry soil.

• The Korean Journal of Ecology
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• v.19 no.2
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• pp.125-139
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• 1996

The relationships between environmental factors and the establishment and growth of oak seelings were studied in the greenhouse. The early seedling performances of three oak species (Quercus mongolica, Quercus serrata, Quercus variabilis) were compared. Mean seed weight was the biggest in Q. variabilis, and the smallest in Q. serrata, and the germination rate was higher in Q. variabilis than in Q. mongolica and Q. serrata. The germination rate was significantly affected by seed weight class in Q. serrata, but not in Q. mongolica. Emergence of oak seedlings was similar in all three oak species, and especially the first leaf emergence increased about twenty days after germination. An experiment was designed using three environmental factors (light, soil moisture, fertilizer) to compare the response of the three oak species. Light and soil moisture significantly affected the seedling height growth of Q. variabilis, but the effect was marginal in Q. mongolica and Q. serrata. However, growth of seedling biomass was significant in all three oak species. In contrast, fertilizer did not affect seedling growth of any of the oak species. Q. variabilis is expected to grow well in large gaps because it is very sensitive and responds well to high light and high moisture conditions. Q. mongolica and Q. serrata are relatively tolerant to shade but may need gaps for the seelings to grow into saplings.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.40 no.4
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• pp.525-532
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• 1995

The periods of germination and seedling emergence, epidermal cell size and the activities of peroxidase and amylase of 6 rice cultivars were examined to clarify the response to 3 temperature conditions, constant temperatures of 27$^{\circ}C$ and 17$^{\circ}C$ and alternating temperature of 24/1$0^{\circ}C$, in the dark condition. The periods of germination and seedling emergence were increased and the germination was delayed greater than the seedling emergence under 17$^{\circ}C$ and 24/l$0^{\circ}C$, compared with 27$^{\circ}C$. Lengths of epidermal cell of coleoptile and first leaf were reduced, but the widths were increased in the 17$^{\circ}C$ and 24/1$0^{\circ}C$, compared with 27$^{\circ}C$. The activities of peroxidase in the emerging shoots and amylase in the germinating seeds were reduced in 17$^{\circ}C$ and 24/1$0^{\circ}C$. There were significant correlations between peroxidase activities and the widths of epidemal cell of first leaf and between amylase activities and periods of germination. Varietal differences of all observations were remarkable in 17$^{\circ}C$ and 24 /1$0^{\circ}C$.