• KOREAN JOURNAL OF CROP SCIENCE
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• v.44 no.3
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• pp.221-224
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• 1999

A field experiment was carried out to observe the weed control effects of vetch and to evaluate vetch characteristics on clay loam soil in no-till direct-sown rice-vetch cropping systems. The effects of weed control, forage productivity, and N content of vetch plants were investigated. With the progress of plant growth, density of Chinese milk vetch (Astragalus sinicus L.) gradually decreased, but densities of foxtail and other weeds decreased steeply due to the depression by the over-shaded vetch canopy in a no-till direct-sown rice-vetch cropping paddy field. The vetch density in tillage systems was lower than in notillage cropping systems. Lower vetch density occurred with an increase in foxtail density and other weeds. Weed control effect increased by the progress of vetch growth, which indicated that the vetch canopy over-shaded the weeds. Vetch straw was degraded rapidly submergence after with water at the time of wet sowing of rice. Early harvesting of vetch seed resulted in lower seed germination. To acquire enough seedlings without re-sowing, the harvesting of seed should be delayed at least 28 days after the flowering stage in order to ensure the vetch population is sustainable in a no-till direct-sown rice-vetch cropping system. In order to improve the survival of vetch plants, vetch seeds should germinate from the heading .stage to before the full-ripening stage of rice plants. To enhance the percent of over-wintering survival, vetch seeds should germinate no later than the end of October in southern Korea. The dry weight of vetch plants increased with the progress of vetch growth until the flowering stage but N content decreased for 30 days from before the flowering stage (2.9%) until the ripening stage (1.8%). We concluded that Chinese milk vetch could have an effect on weed control before the flowering stage, sustainability without re-sowing of seed annually, and effective green manure for rice pre-crop in no-till direct-sown rice-vetch relay cropping systems.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.14
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• pp.159-164
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• 1973

This study was carried out in the central part of Korea for three years from 1970 to 1972. Its aim was to investigate the variations of growth and yield of rice varieties of different cultivating methods (transplanting culture, direct sowing culture on irrigated paddy field, and direct sowing culture on non-irrigated paddy field. The results could be summarized as follows; 1. The number of days from sowing to heading by direct sowing culture on irrigated paddy field was remarkably shorter than transplanting culture. Direct sowing culture on non-irrigated paddy field was longer than transplanting culture. 2. The number of panicles showed direct sowing culture on irrigated paddy field was first, direct sowing culture on non-irrigated paddy field was second, and third transplanting culture. But the number of spikelets per panicle was first on the transplanting culture, second on the direct sowing culture on non-irrigated paddy field and third on the direct sowing culture on irrigated paddy field. 3. The weight of the brown rice showed that direct sowing culture on irrigated paddy field produced the highest yield among the cultivating method in all varieties. The transplanting culture increased more than the direct sowing culture on non-irrigated paddy field. The highly productive varieties were Sadominory, Akibale, Suwon 213-1 when the direct sowing culture on irrigated paddy field was used. 4. The correlation between the brown rice yield and the yield components were as follows; in each cultivating method, it showed highly significant positive correlation between the brown rice yield and the 1, 000 grain weight of hulled rice, and between the brown rice yield and the number of the spiklets per panicle in the transplanting culture, in the direct sowing culture On irrigated paddy field between the brown rice yield and the number of spikelets per panicle and between the brown rice yield and the number of panicles, in direct sowing culture on non-irrigated paddy field between the brown rice yield and number of panicles. 5. It showed highly significant negative correlation between the brown rice yield and the number of days from sowing to heading in the direct sowing culture on irrigated and non-irrigated paddy field, but it was showed very low negative correlation in the transplant culture.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.44 no.2
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• pp.149-153
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• 1999

Prediction of rice developmental stage is necessary for proper crop management and a prerequisite for growth simulation as well. The objectives of the present study were to find out the relationship between the plastochrone index(PI) and the developmental index(DVI) estimated by non-parametric phenology model which simulates the duration from seedling emergence(DVI=0) to heading(DVI=l) by employing daily mean air temperature and daylength as predictor variables, and to confirm the correspondency of developmental indice to panicle developmental stages based on this relationship. Four japonica rice cultivars, Kwanakbyeo, Sangpungbyeo, Dongjinbyeo, and Palgumbyeo which range from very early to very late in maturity, were grown by sowing directly in dry paddy field five times at an interval of two weeks. Data for seedling emergence, leaf appearance, differentiation stage of primary rachis branch and heading were collected. The non-parametric phenology model predicted well the duration from seedling emergence to heading with errors of less than three days in all sowings and cultivars. PI was calculated for every leaf appearance and related to the developmental index estimated for corresponding PI. The stepwise polynomial analysis produced highly significant square-rooted cubic or biquadratic equations depending on cultivars, and highly significant square-rooted biquadratic equation for pooled data across cultivars without any considerable reduction in accuracy compared to that for each cultivar. To confirm the applicability of this equation in predicting the panicle developmental stage, DVI at differentiation stage of primary rachis branch primordium was calculated by substituting PI with 82 corresponding to this stage, and the duration reaching this DVI from seedling emergence was estimated. The estimated duration revealed a good agreement with that observed in all sowings and cultivars. The deviations between the estimated and the observed were not greater than three days, and significant difference in accuracy was not found for predicting this developmental stage between those equations derived for each cultivar and for pooled data across all cultivars tested.

• Korean Journal of Plant Resources
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• v.29 no.4
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• pp.511-518
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• 2016

The subject of this experiment is to supply basic data to inhibit non-productive tillers which are uneconomical for mechanical harvesting and to evaluate optimum planting density and sowing date in central district. Total number of tillers and effective first and second of tillers according to different planting density was higher in 80 ㎝ ridge than 60 ㎝ ridge in proso millet. The wider between plant distance on the ridge, the more increased total number of tillers and effective first and second of tillers. The highest effective tillers (91.7 %) in the first tillers was obtained from the second sowing date (23 May) among different sowing date and next is in the order of 3^rd(13 June, 89.8%) > 1^st(2 May, 85.6%) > 4^th(4 July, 85.2%). The percentage of effective tillers in the second tillers was decreased in the order of 2 May (53.7%), 23 May (40.7%), 13 June (22.2%), 4 July (0%) as the sowing date was delayed. There was no significant difference in days to heading and days to ripening according to different planting density. Although culm length was increased as planting density was increased, whereas number of tillers, stem diameter, ear length, grains per ear and 1000 grain weight was decreased. In the growth and yield characteristics of proso millet according to different sowing date, days to heading and days to ripening, culm length, stem diameter, ear length, grains per ear and yield per 10a were decreased. After the sowing date of 13 June, the reduction of growth and yield characteristics were higher because of excess-moisture injury.

• Korean Journal of Plant Resources
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• v.30 no.4
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• pp.427-434
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• 2017

This experiment was conducted to investigate the aspect of tiller occurrence, growth and yield of sorghum according to planting distance and sowing date. The object of this experiment is to get basic data to inhibit non-productive tillers uneconomical and cumbersome for mechanical harvesting. Also another object was to evaluate optimum planting distance and sowing date in central district area. Total number of tillers was more in 80 cm ridge than 60 cm ridge and it was increased as the planting distance was wider from 15 cm to 30 cm on the each ridge. Ratio of effective tillers was higher in 60 cm ridge than 80 cm ridge and it was decreased as planting distance was wider from 15 cm to 30 cm. The lower the planting distance, the more increased total number of tillers, whereas effective tillers was decreased as planting distance was high. Average of total number of tillers of three varieties was higher in sowing date of May 2 (1st sowing date), whereas ratio of effective tillers was the highest in sowing date of May 23 (2nd sowing date). Hwanggeumchal showed the highest total number of tillers (1.2 tillers), while Moktaksusu had the lowest total number of tillers (0.8 tillers) among three varieties. There were no significant difference between planting distance and days to heading and ripening date from seeding. Culm length increased as planting distance was high, but ear length, grains per ear and 1000 grain weight were decreased on the other hand. The highest yield of sorghum per 10a was obtained from $60{\times}20cm$ planting distance among 6 planting distances.

• Korean Journal of Agricultural Science
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• v.9 no.1
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• pp.231-238
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• 1982

The study was done to determine the proper transplanting dates and seedling ages of rice when mechanical transplanting was attempted. Heading dates of the Milyang #23, developed from Tong-il rice was delayed by delayed transplanting and the percent of filling grain was also low. The proper heading dates for the variety should be the first part of August and the transplanting should be done by the end of May. The presumed last days for the transplantation was considered early part of June. 30 to 40 days old seedlings were very effective to have healthy rooting systems. However, the Milyang #15 had shown more tolerance to the late transplantation than Milyang #23 and the degree of delaying heading dates due to the delayed transplantation was rather smaller than that of the Milyang #23. Even when the Milyang #15 was transplanted on June 30, the heading dates were around the middle of August and the ripening percentage was comparatively high and yield was also high. Therefore, the proper heading dates of the Milyang #15 might be around the middle of August and transplanting dates should be the first part of June. The possible last dates of transplantation of the Milyang #15 was assumed to be the last days of June and the proper seedling ages would be 20 to 30 day after sowing.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.67 no.3
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• pp.180-188
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• 2022

This study was conducted to determine the optimal sowing date for seed yield of summer oat (Avena sativa L.) cultivars "Darkhorse (DH)" and "Highspeed (HS)" in Wanju, Jeonbuk province between 2017 and 2018. We investigated seed yield from 4 sowing dates: July 15, July 30, August 15, and August 30. We evaluated the agronomic characteristics of summer oats (DH and HS). We found the heading date of all cultivars to be within 50 days. Delayed sowing resulted in significantly increased plant height for both years and cultivars. There was no significant difference in spike length of DH and HS which ranged from 12.8 to 17.8 cm. The sowing date of July 30 produced a higher number of grains per spike, but this yield differed significantly by year and cultivars. In 2017, the first sowing resulted in the lowest DH yield at 132 kg per 10a, while the second sowing had the highest yield at 227 kg. HS yield was the lowest in the first sowing at 126 kg and the highest in the third sowing at 219 kg. In 2018, DH had the lowest yield from the first sowing at 184 kg per 10a, and the highest from the second sowing at 240 kg, but there was no significant difference between these yields. The first sowing for HS gave the lowest yield at 160 kg, and the second sowing produced the highest at 258 kg. The germination rate of harvested seeds from each sowing date in 2017 and 2018 was found to be higher than 85% and there was no significant difference between the two cultivars in the 2018 germination rate test. Thus, we found the optimal sowing date for summer cultivation of oats for the highest seed yield to be between July 30 (second sowing) and August 15 (third sowing).

• KOREAN JOURNAL OF CROP SCIENCE
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• v.40 no.2
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• pp.236-244
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• 1995

This study was carried out to clarify the changes in dry matter weight and physicochemical property of job's tears grain during ripening period. Four varieties of job's tears were seeded at April 20, May 10, and May 30, andgrains were harvested at every 7 days from heading to maturity, The whole seed weight of thick hull varieties, Kimje and Aewon, was higher than that of improved thin hull varieties, Suwon 3 and Suwon 6, from heading to maturity, However, the dehulled grain weight of thin hull variety were higher than that of thick hullvariety from 35 days after heading. The first heading spikelet showed lower 100-grain weight com-pared with the spikelets headed at full blooming stage among the same plant. The increased rate of de hulled grain weight during maturing period was higher in thin hull variety than thick hull one, later seeding date than early seeding, and intermediate headed spikelet than early head-ed one, respectively. As maturing proceeds the protein content of de hulled grain was decreased, alkali digestibility value(ADV) showed a rising trend, and little change was found in gel consistency of milled grain flour. And same trends were found in protein content, ADV and gel consistency as the seeding date was delayed. Among amylogram properties of job's tears flour the maximum, minimum, and final viscosity as well as breakdown were decreased, and set back was increased in later seeding plots

• KOREAN JOURNAL OF CROP SCIENCE
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• v.37 no.2
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• pp.123-133
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• 1992

This study was conducted to clarify progressed changes of plant types and the effects of the physiological and ecological components on improving ideotype of winter wheat. 12 wheat varieties were planted at the experimental farm of Wheat and Barley Research Institute in Suwon in 1990. As results of intensive wheat breeding for early maturity since 1959, heading, flowering and maturing dates have been shortened by 17, 15 and 14 dagys, respectively. The shortened days from sowing to heading and from heading to flowering contributed to the early maturity to improved. Physiological factors associated with heading time of wheat could be reprsented by growth habit, photoperiod responses, earliness in narrow sense and winter hardiness. For improving an early maturity of winter wheat, it would desired to maintain some degree of winter habit(III-IV), and recombination of more insensitivity to short day length and more shortened earliness in narrow sense than that of Saemil and Chugoku 81, and higher degree of winter hardiness. For improving the early maturity the more effective way must be of shortened days from sowing to heading, and days from flowering to maturity than days from heading to flowering. Ideotype of wheat will be desired to recombine two semi-dwarf genes with erect plant type being about 70-80cm, less stem elongation by late spring, long spike and many grains per spikelet. Average spike weight ratio was about 45-49% in high-yielding varieties, stem fresh weight was lighter, but spike fresh weight was heavier in new one while leaf fresh weight was similar to each other during the maturing periods. Average spike dry weight ratio was higher about 40～48%, and stem and leaf blade dry weights were lower in the newly bred varieties. Stem dry weight was heavier than spike or leaf dry weight in the old varieties of Yungkwang, Jangwang and Jinkwang. Leaf area index for the varieties showed normal distribution curve as the maximum point in booting stage. The maximum point of this curve come in early maturing wheat, and late in old one. The maximum points of LAI were 6.4～6.8 in the high-yielding varieties. Totals of LAI in each period investigated of old one were higher than those of newly bred being 24.6～28.8. Chlorophyll content of the high-yielding varieties of Chokwang, Geurumil and Saemil as higher than that of the old varieties Jangkwang, Jinkwang, Wonkwang and Sinkwang from regrowing period to April 21. after then slightly and even after heading. Net assimilation rate (NAR) was higher in high-yielding varieties with good plant type, and lower in old ones. Grain yield of the newly released varieties increased rapidly but slowly in the old ones. Change in water content of grain at the growing stage in newly bred was lower than that of the old bred. Diminishing rate of water content of grain in establishment per day was 1.2% average that of the old varieties including Yungkwang was 1.5%, and those of the newly bred including Chokwang were 0.9～1.1%. Chokwang, Naemil, and Saemil were the highest-yielding varieties of the Korean cultivars. Yields were increased by spikes per m$^2$, grain weight for the varieties bred in Suwon, and by spikes per m$^2$ for the varieties bred in Milyang.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.63 no.4
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• pp.282-293
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• 2018

The heading response of rice varieties is determined by the combined effects of their basic vegetative phase (BVP), photoperiod-sensitivity (PS), and thermo-sensitivity (TS). This study was performed to analyze the effect of differences among heading ecotypes of rice on their heading response in the field. To do this, we investigated the heading response of 15 varieties grown under different day-length and temperature conditions in a phytotron. The characteristics of heading ecotypes were compared to the heading responses in the field-grown rice varieties that were used in the phytotron experiments. The ranges of these characteristics across the 15 varieties were 18 - 35 days for BVP, 12 - 61 days for PS, and 12 - 35 days for TS. In comparisons of coupled varieties that differed only in a single trait among BVP, PS, and TS, the variety with the longer BVP and that with the higher PS had a longer period from sowing to heading (DTH), while the variety with the higher TS had a shorter DTH. The comparative magnitude of DTH in the coupled varieties followed the PS trait when BVP and PS were involved, the BVP trait when BVP and TS were involved, and the PS trait when PS and TS were involved in the heading response of field-grown rice. When comparing the coupled varieties with different traits of the three examined factors, the heading response was consistent with the PS trait. The DTH in all 15 varieties was significantly correlated with the PS, and the DTH in 9 selected varieties with a relatively small PS was correlated with BVP. The reduced DTH of rice in the July 10 seeding treatment compared to those in the June 25 and May 11 seeding treatments was positively associated with PS, but not with TS. We concluded that the heading response of rice varieties under natural conditions in Korea is mainly governed by the PS trait and is also greatly affected by the BVP trait when the PS is small.