• KOREAN JOURNAL OF CROP SCIENCE
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• v.53 no.1
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• pp.42-49
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• 2008

GDD models of corn were developed in bare soil, while sweet and super sweet corns are grown under black polyethylene (P. E.) film mulch in Korea. To develop a suitable GDD model under black P. E. film mulch, a super sweet com hybrid "Cambella-90" was planted from 1 April to 30 June in 2003 at the 10-day intervals under black P. E. film mulch and in bare soil. In bare soil the best GDD model was $GDD\;=\;{\sum}[H"+L')/2\;-\;10^{\circ}C]$, where H" was daily maximum temperature but is was substituted for $30^{\circ}C$ - (daily maximum temperature - $30^{\circ}C$) when higher than $30^{\circ}C$ and L' was daily minimum temperature, but it was substituted for $10^{\circ}C$ when lower than $10^{\circ}C$. The same GDD model could be adapted for com grown under black P. E. film mulch, but base temperature was substituted for $9^{\circ}C$. To determine planting date for the scheduled harvests, accumulated GDDs were calculated using 30-year average temperature data during the growing season. Under black P. E. film mulch planting dates were determined by subtracting GDD of the hybrid, $970^{\circ}C$, from accumulated GDD of scheduled harvest dates.

• Journal of Bio-Environment Control
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• v.32 no.3
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• pp.242-248
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• 2023

This study was conducted to evaluate the effects of trinexapac-ethyl (TE) and prohexadione-calcium (PC) on the growth and turf quality of perennial ryegrass (Lolium perenne L.). Treatments were designed as follows; control (non-treatment), TE (TE 0.01 a.i. g·m^-2·100mL^-1), and PC (PC 0.01 a.i. g·m^-2·100mL^-1). Compared with control, turf color index and chlorophyll content of TE and PC treatments were not significantly different. As applied plant growth regulators (PGRs), shoot length in the TE and PC was decreased by 8.9-12.4% and 6.7-13.6%, respectively, and clipping yield by 44.4-45.8% and 40.6-40.9%. When evaluated with the growth of shoot length after applying PGRs, residual days of TE and PC were 43.6 and 37.9 days after treatment of PGRs (DAT) in the 1st experiment (July 29-August 26), respectively, and 38.3 and 39.5 DATs in the 2nd experiment (September 30-October 28). These results indicated that an application of TE or PC decreased shoot length and clipping yield in the perennial ryegrass, and their residual time was about 40±3 DATs. Perennial ryegrass applied with PGRs like TE and PC was not significant seasonal difference, and might be not phytotoxic.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.49 no.3
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• pp.188-193
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• 2004

Fifty-day-old plug seedlings of yacon (Polymnia sonchiflolia Poeppig ＆ Endlicher) were transplanted on Mar. 23, Apr,8, Apr,23, May 8, May 23, and June 7,2002 at Jeju to evaluate the effect of transplanting date on the growth and yield of yacon in Jeju island. Delaying the transplanting until May 23 greatly decreased plant height stem height, main stem diameter and number of nodes per plant. The number of marketable tuberous roots was about 6.0 per plant with the early transplanting from March 23 to April 231 but decreased to 1.9 per plant with the latest transplanting time, June 7. The yield of marketable tuberous roots of early transplanted (March 23 to April 23) yacon was about 27 MT/ha, and was 32.4 MT/ha at April 23 transplanting, but was remarkably reduced at the three later transplantings, May 8, May 23, and June 7. Dry matter and soluble solid contents of marketable tuberous roots were 14％ and 15％, respectively, regardless of transplanting date. The weight of a marketable tuberous root ranged from 153 to 183.9 g at the first three transplantings, but gyeatly reduced with delaying transplanting until May 7. The optimum transplanting date for yacon in Jeju island seems to be from mid-April to late April considering tuberous root yields, the risk of late-spring frost, and cost of seedling raising.

• Journal of The Korean Society of Grassland and Forage Science
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• v.26 no.3
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• pp.155-158
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• 2006

This study was carried out to find out the effect of seed date and rate on the agronomic characteristics and yield of forage barley in paddy field of Suwon, from 2001 to 2003. The main plots were consisted of different seeding dates such as 5th and 20th October and 5th November. The subplots were consisted of different seeding rates of barley such as 160, 190 and 220 kg/ha. Plant height was increased at the early seeding. Dry matter(DM) percentage of barley was decreased as the seeding date was delayed. Dry matter percentages of 5th and 20th October and 5th November were 47.4, 41.5 and 34.5%, respectively. Fresh matter yield of barley decreased from 30,092 to 16,018 kg/ha as the seeding date was delayed. And fresh matter yield of barley was significantly increased with the increase in the seeding rate. Dry matter yield of barley decreased from 14,230 to 5,521 kg/ha as the seeding date was delayed. And dry matter yield of barley was significantly increased with increase in the seeding rate(p<0.05). The results obtained from this study indicate that both the seeding date of 20th October and seeding rate of 220 kg/ha would be recommendable for forage yield of barley in paddy field.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.54 no.2
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• pp.218-224
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• 2009

In organic fanning systems, integration of cover crops into cropping system are recommended to improve the soil quality, to prevent soil erosion, and to provide biological control of weeds. The aim of the present study was to evaluate the optimal seeding dates of major cover crops. To know optimal seeding dates, crimson clover, alfalfa, rye and hairy vetch were sown on 20. Sep., 27. Sep., 4. Oct., 11. Oct., 18. Oct., 25. Oct. Rye could germinate and grow well in all the tested sowing dates. Hence, it was concluded that the sowing of rye could be conducted later in fall or more earlier in spring than any other cover crops tested in this study. Growth and ground covering capacity were significantly decreased by late sowing in alfalfa and crimson clover. For safe overwintering, alfalfa and crimson clover should be sown before late September. Similarly, field emergence of hairy vetch was found to be sensitive to soil temperature, however, its growth and ground covering capacity after overwintering was enough to compensate the delay in sowing. Germination tests in laboratory revealed that hairy vetch grew faster at $25^{\circ}C$ compared to $20^{\circ}C$. The result suggested that germination and growth rate of hairy vetch was rapidly decreased at low temperature. Therefore, it is recommended that hairy vetch should be sown as soon as possible in September for improving stand establishment after overwintering.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.61 no.3
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• pp.208-214
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• 2016

This study was conducted to evaluate the effects of different sowing times (May 25, June 10, June 25, July 10, and July 25) on growth and yield of four proso millet (Panicum miliaceum L.) cultivars (Hwanggeumkijang, Manghongchal, Ibaekchal, and Hwangsilchal) at a cultivation area in Iksan, Jeonbuk Province. Heading and ripening times were delayed, with later sowing times in all cultivars, and the periods for heading and ripening were shortened. For sowing from May 25 to July 25, the growth stage was shorter by 40 days in Manghongchal, 38 days in Hwanggeumkijang, 36 days in Hwangsilchal, and 30 days in Ibaekchal. The culm length, ear length, ear width, and culm diameter differed significantly between the cultivars and sowing times. In particular, the culm and ear lengths were considerably reduced when the sowing time was delayed. The grain yield (kg/10a) of Hwanggeumkijang and Ibaekchal was 312 and 359 kg, respectively, for sowing on June 10; and that of Manhongchal and Hwangsilchal was 286 and 404 kg, respectively, for sowing on June 25. Thus, the optimum sowing time was June 25 for Hwanggeumkijang and Ibaekchal, and June 10 for Manhongchal and Hwangsilchal.

• Journal of The Korean Society of Grassland and Forage Science
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• v.32 no.3
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• pp.265-274
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• 2012

This study was carried out to investigate the growth characteristics, yield and chemical compositions of corn hybrids for silage according to ridging times in the paddy field cultivation. The experimental design was arranged in a randomized block design with five treatments and three replication. The ridging times of five treatments were untreated (C), 7 leaves (T1: 31 days), 8 leaves (T2: 37 days), 9 leaves (T3: 42 days) and 10 leaves stage (T4: 48 days after sowing) of silage corn. The ridging treatments (T1, T2, T3, T4) were higher (p<0.01) dry matter yield and TDN yield than the unridging treatment (C). However, there were no significant differences among T1, T2, T3 and T4 treatments. The Crude protein content of unridging treatment was decreased (p<0.01), while NDF content was increased (p<0.01) compared to ridging treatments. The contents of mineral and amino acid in ridging treatments were higher than unridging treatment (p<0.05, p<0.01). In particular, mineral and amino acid contents were the highest in T4 and T1, respectively (p<0.01). Based on the above results, ridging work is to be increased the yield quantity and nutritional value of silage corn. And the best result was obtained in T4 treatment of ridging treatments.

• FLOWER RESEARCH JOURNAL
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• v.18 no.1
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• pp.33-37
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• 2010

Effects of cutting time of double flowered Hydragea serrata for. acuminata native to Korea on flowering and growth of following year were investigated in order to develop as a pot plant. Cuttings were carried out every 10th day from April to September in 2008. The cuttings were directly placed in 15 cm diameter pots. Longest plant was obtained from May cuttings and their average heights were 31.7 cm, and followed by April and July cuttings. Plant heights of August and September cuttings were 23.6 cm and 22.0 cm, respectively. In contrast, growth and height of June cutting were abnormally small. Leaf length, leaf width and petiole length of August and September cutting were reduced, but numbers of leaves were not changed. Average flower cluster numbers of May cuttings were 4 flower clusters, and July, August and September cuttings were 3 clusters while only 1 flower cluster per a plant was obtained during June. Biggest diameter of flower crown was observed from May cuttings and the size was 10.3 cm diameter; however, smaller flower crown size was observed after July cuttings. The best overall flower appearance was observed from May cuttings, and the worst was June cuttings. Even though plant height of August and September cuttings were reduced, flowering aspect and ornamental value were normal, but blooming times were retarded according to late cutting time.

• Journal of Practical Agriculture & Fisheries Research
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• v.20 no.1
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• pp.75-87
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• 2018

This study was carried out to investigate the effects of planting time on the survival rate and growth. Ilex cornuta Lindl., I. aquifolium 'Silver Queen', Ardisia pusilla 'Variegata', and Rhododendron indicum(Satsuki azalea) were planted in pottery pot six times such as April 1, June 1, July 1, August 1, October 1, and December 1 in 2017. The survival rate of I. cornuta Lindl. planted in April, October, and December was 100%, whereas the survival rates were 90% in June, 50% in July, and 60% in August, respectively. The survival rates of I. aquifolium 'Silver Queen' and R. schlippenbachii were also shown about 60% in July and 70% in August, which were lower than in the other planting times at 100%. However, the survival rate of A. pusilla 'Variegata' was shown 100% in the all planting times. The growth rates of plant length, plant height or leaf length or any others of I. cornuta Lindl. were shown 20.0%, 15.5% and 16.5% planted in June, July, and August, respectively, while those planted in April, October and December were 3.2%, 12.3% and 10.7% respectively. Similarly, the growth rates of leaf numbers and plant length of I. cornuta Lindl., A. pusilla 'Variegata', and R. indicum(Satsuki azalea) planted in summer season from June to August for all plat (not only leaf numbers and plant length in was facilitated, while the growth was restrained in planting for spring or autumn. Therefore, the plantation during summer is better for increasing the survival rate and promoting the growth.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.40 no.2
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• pp.150-156
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• 1995

Planting date is the most important factor in determining winter survival of Crop plants. The objective of this study was to explore the effect of planting date on the development of freezing tolerance and winter survival of canola. Six winter cultivars were planted at three different dates during the fall on the Michigan State University Research Farm at East Lansing, MI. Freezing tolerance was determined by ion leakage tests every 15 days after planting until middle of November. Winter survival was evaluated by counting the live plants in the fall and next spring. Planting date as well as cultivar treatment had a significant effect on freezing tolerance and winter survival A different pattern in development of freezing tolerance was observed for different planting dates. There was a high correlation between freezing tolerance and winter survival suggesting that freezing tolerance could be a useful predictor for winter survival.