• KOREAN JOURNAL OF CROP SCIENCE
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• v.50 no.spc1
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• pp.85-87
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• 2005

This study was conducted to identify the effective dyainage-time influencing rice yield and grain quality on a reclaimed saline soil, the experiment conducted at the Gyehwado substation of the Honam Agricultural Research Institute from 2002 to 2003. The experimental field contained $0.1\%\;and\;0.3\~0.4\%$ NaCl in soil solution, respectively. The experiment involved salinity levels as main plot and sub-plot where consisted of 6 treatments in a split plot design with three replicates. Rice yield performance showed a maximum at drainage-time for 35 days after flowering under medium salinity level, but indicated only $64\%$ of yield level compare to low soil salinity. Percentage of well-shaped rice was high in low soil salinity indicating there aye severe affection for grain quality in medium soil salinity regardless water drainage-time.

• Journal of Bio-Environment Control
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• v.31 no.4
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• pp.432-437
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• 2022

In this study, strawberries were grown during the two cultivation periods (first: 2020-2021, second: 2021-2022) to analyze the effect of the external light environment and growing degree days (GDD) on crop production. The temperature and humidity during day in a greenhouse in each cultivation period were similarly managed. At night, there was a statistical difference in temperature and humidity in the greenhouse between two periods. The accumulated solar radiation during the first cultivation period was high in September and October. Since January, the accumulated solar radiation during the second cultivation period was high. In the second cultivation period, the initial yield was small because the accumulated solar radiation and GDD was small. But accumulated yields and potential maximum yields in second cultivation period were larger than yields in the first cultivation period as the accumulated solar radiation and GDD increased. The sugar contents of strawberry decreased as GDD increased.

• Journal of Bio-Environment Control
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• v.21 no.3
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• pp.271-275
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• 2012

The average annual and winter ambient air temperatures in Korea have risen by $0.7^{\circ}C$ and $1.4^{\circ}C$, respectively, during the last 30 years. The continuous rise in temperature presents a challenge in growing certain horticultural crops. Chinese cabbage, one most important cool season crop, may well be used as a model to study the influence of climate change on plant growth, because it is more adversely affected by elevated temperatures than warm season crops. This study examined the influence of transplanting time, nitrogen fertilizer level and climate parameters, including air temperature and growing degree days (GDD), on the performance of a Chinese cabbage cultivar (Chunkwang) during the spring growing season to estimate crop yield under the unfavorable environmental conditions. The chinese cabbage plants were transplanted from Apr. 8 to May 13, 2011 when 3~4 leaves were occurred, at internals of 7 days and cultivated with 3 levels of nitrogen fertilization. The data from plants transplanted on Apr. 22 and 29, 2012 were used for the prediction of yield as affected by planting date and nitrogen fertilization for spring production. In our study, plant dry weight was higher when the seedlings were transplanted on 15th (168 g) than on 22nd (139 g) of April. There was no significant difference in the yield when plants were grown with different levels of nitrogen fertilizer. The values of correlation coefficient ($R^2$) between GDD and number of leaves, and between GDD and dry weight of the above-ground plant parts were 0.9818 and 0.9584, respectively. Nitrogen fertilizer did not provide a good correlation with the plant growth. Results of this study suggest that the GDD values can be used as a good indicator in predicting the top biomass yield of Chinese cabbage.

• Korean Journal of Remote Sensing
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• v.27 no.2
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• pp.191-201
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• 2011

Soybean has widely grown for its edible bean which has numerous uses. Microwave remote sensing has a great potential over the conventional remote sensing with the visible and infrared spectra due to its all-weather day-and-night imaging capabilities. In this investigation, a ground-based polarimetric scatterometer operating at multiple frequencies was used to continuously monitor the crop conditions of a soybean field. Polarimetric backscatter data at L, C, and X-bands were acquired every 10 minutes on the microwave observations at various soybean stages. The polarimetric scatterometer consists of a vector network analyzer, a microwave switch, radio frequency cables, power unit and a personal computer. The polarimetric scatterometer components were installed inside an air-conditioned shelter to maintain constant temperature and humidity during the data acquisition period. The backscattering coefficients were calculated from the measured data at incidence angle $40^{\circ}$ and full polarization (HH, VV, HV, VH) by applying the radar equation. The soybean growth data such as leaf area index (LAI), plant height, fresh and dry weight, vegetation water content and pod weight were measured periodically throughout the growth season. We measured the temporal variations of backscattering coefficients of the soybean crop at L, C, and X-bands during a soybean growth period. In the three bands, VV-polarized backscattering coefficients were higher than HH-polarized backscattering coefficients until mid-June, and thereafter HH-polarized backscattering coefficients were higher than VV-, HV-polarized back scattering coefficients. However, the cross-over stage (HH > VV) was different for each frequency: DOY 200 for L-band and DOY 210 for both C and X-bands. The temporal trend of the backscattering coefficients for all bands agreed with the soybean growth data such as LAI, dry weight and plant height; i.e., increased until about DOY 271 and decreased afterward. We plotted the relationship between the backscattering coefficients with three bands and soybean growth parameters. The growth parameters were highly correlated with HH-polarization at L-band (over r=0.92).

• Journal of Bio-Environment Control
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• v.23 no.4
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• pp.364-370
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• 2014

The nutrient and irrigation management of scion and rootstock can alleviate stress on grafted transplants after grafting and promote the growth. This study investigated the effects of nutrient and irrigation management of scion and rootstock on the graft-take and growth of grafted pepper transplants. Before grafting, the scions were subjected to different water potential regimes in media by controlling the irrigation frequency and time. The scions were subirrigated 0, 1(two days before grafting), 1(one days before grafting) or 2 times for five days before grafting. The irrigation frequency and time influenced the water potential of media and the growth of scion and grafted transplants. At 13 days after grafting, fresh and dry weight of transplants which were irrigated once at two days before grafting were greater by 29 and 34% than those without irrigation during five days before grafting. This suggests that mild water stress on scion prior to grafting by controlling water management alleviate water stress on grafted transplants after grafting and improve the growth. Before grafting, the rootstocks were subjected to different nutrient regimes by controlling nutrient solution application. The rootstocks were supplied with nutrient solution 0, 1, 2, or 4 times. The nutrient application frequency and time influenced the electrical conductivity (EC) and pH of media. Accordingly, the growth and mineral contents of rootstock and grafted transplants were also affected. At 13 days after grafting, fresh and dry weight of transplants with four times of nutrient application increased by 30 and 20%, respectively, than those without nutrient solution supply during seven days before grafting. Therefore, it is recommended that nutrient solution be supplied more than four times during seven days before grafting for the production of high quality transplants.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.50 no.6
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• pp.369-377
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• 2005

Precise application of topdressing nitrogen (N) fertilizer is indispensible for securing high yield and good quality of rice and minimizing N losses to the environment as well. For precise N management, growth and nitrogen nutrition status (NNS) should be diagnosed rapidly and accurately. The objective of the study was to evaluate the applicability of vegetation index (VI) calculated from hyperspectral canopy reflectance measurement and SPAD reading to nondestructive in situ diagnosis of growth and NNS of rice. Canopy reflectance, SPAD read­ing, growth parameters, and NNS characteristics were measured from various N treatments to evaluate the relationships among them for two cropping seasons from 2001 to 2002. The correlation coefficient of VIs with variables of growth and NNS increased positively as rice canopy became more closed. Regardless of growth stages, VIs had significantly high correlations with LAI, shoot dry weight (DW), shoot N content and nitrogen nutrition index (NNI). Those correlation coefficients increased steadily before heading stage as rice grew up. However, tiller number and leaf N concentration showed significantly high correlations with VIs only at and after panicle initiation stage (PIS). Among the VIs, RVIgreen had significantly higher correlation with the measured parameters than the other VIs: it showed correlation coefficients greater than 0.8 with leaf and shoot N concentration and DW, and much higher coefficients greater than 0.9 with LAI, shoot N content, and NNI. At LAI of below 2.5, VIs had non-significant or low correlations with the growth and NNS indicators due to the background effects. SPAD reading had significantly high correlation with leaf N concentration and NNI at each growth stage. In addition, it had significant correlations with variables of growth and NNS at PIS and booting stage, particularly, at booting stage. Though SPAD reading had a significantly high correlation value at a given growth stage in each year, it showed very weak relationship with variables of growth and NNS when pooled across growth stages and years. In conclusion, RVIgreen was found to be the most reliable VI to estimate the growth and NNS of rice around at PIS, but SPAD reading had much limitations.

• 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.

• 한국약용작물학회:학술대회논문집
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• 2011.09a
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• pp.320-321
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• 2011

• 한국약용작물학회:학술대회논문집
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• 2011.04a
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• pp.234-235
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• 2011

• 한국약용작물학회:학술대회논문집
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• 2011.04a
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• pp.294-295
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• 2011