• Korean Journal of Weed Science
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• v.7 no.1
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• pp.45-51
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• 1987

This experiment was conducted to find out the critical competitive period and competitive ability of rice against red rice. Plant height and number of tillers of rice decreased as red rice competed with rice during active tillering stage. The maximum tillering stage of rice competed with red rice became about 10days earlier than those non-competed. Significant yield reduction of rice was observed in the plots competed for 20 days after transplating or longer. Such a yield reduction can be mainly attributed to the decrease in number of panicles per hill and grain number per panicle. In a replacement diagram for rice and red rice, their competition is turned out being antagonized. The relative yield total was considered lower than 1. Grain number, culm and panicle length of rice was not affected significantly by inter-specific competition. Rice grain yield reduction was highly correlated with the number of panicles of red rice. Three hundred panicles/$m^2$ of the red rice were necessary to reduce rice grain yield by 50% of the check plot.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.42 no.6
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• pp.752-758
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• 1997

Urea, which is the major nitrogenous fertilizer used in Korea, has been used inefficiently in direct-seeding on dry soil by farmers. This study was conducted to investigate changes in concentrations of basal N within soil layers and its loss during early stage of rice growth. Urea fertilizer was applied in the rates of 7, 5.25, 3.5, 1.75, 0kg- N /10a under direct-seeded rice in dry paddy soil. The concentrations of ammonium and nitrate were determined in soil samples with different depths during period from seeding to the 3rd leaf stage. Futhermore, N leaching was measured in lysimeter designed with pot in greenhouse. ${NH_4}^+ \; and\; {NO_3}^-$ adsorption by soil increased with increasing concentration of added urea and decreased as deeper in soil layers. ${NH_4}^＋$ concentration reached its peak at 7 days after urea application (DAA) and disappeared almostly at 14 DAA. ${NO_3}^-$ reached its peak at 10 DAA and decreased slowly until 14 DAA. ${NO_3}^-$N leaching started next day after urea application and completed until 11 DAA. We concluded that most of basal N applied to direct-seeded paddy was lost by leaching and not useful for rice plant which was in stage of germination. It is urgent need to develop new nitrogen application method for direct-seeding rice on dry soil.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.42 no.6
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• pp.766-777
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• 1997

The purpose of this study was to investigate inheritance modes of low temperature germinability(LTG) on rice. Two experiments were carried out: In experiment I, the seeds of 10 rice varieties yielded at the different cultivation conditions which were transplanted in a paddy field from May 20 to July 5 with 15-day interval, were tested at fixed temperature (13$^{\circ}C$) in-door and at field with natural conditions to find out the change of LTG according to different cultivating condition among the each variety, In experiment II, F$_1$ seeds of full diallal cross from six parents, were analyzed for combining ability and reciprocal differences of low temperature germinability. The results are summarized as follows. The seeds of 10 varieties showed significant differences of LTG at the different cultivation conditions, varieties and their interaction. And the relationship between LTG coefficient at 13$^{\circ}C$ and low temperature emergence(LTE) coefficient at field was highly significantly positive(r=0.511). From the analysis of the diallel cross, high significance was found at reciprocal difference and alpha inheritance. The mean squares of general combining ability(GCA) and specific combining ability of LTG were highly significant with higher mean squares of GCA. Seventeen out of 30 cross combinations showed transgressive segregation.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.53 no.4
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• pp.382-387
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• 2008

This study was conducted to determine the effect of rice bran on rice yield, grain quality and weeds control depending on applying times. The redox potential was severely reduced $4{\sim}7$ days after rice bran application but that of conventional practice was reduced 17 days after transplanting. During the decomposing of the rice bran in the water, the dissolved oxygen in the water was exhausted right away after rice bran application. The dry weight of weed increased as the rice bran application time was delayed that weed dry weights increased by 138% in applying before puddling (ABP), 219% in 5 DAT (days after transplanting), 300% in 7 DAT and 619% in 9 DAT compared to conventional practice. The rice yield reduced remarkably in rice bran treatments after transplanting compared to conventional practice and applying before puddling. In the rice quality, the head rice ratio in the rice bran treatment was higher than that in conventional practice, and its protein content decreased. The results confirm that the rice bran application make the rice palatability higher, but there was no difference in rice qualities depending on application times.

• Korean Journal of Agricultural and Forest Meteorology
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• v.2 no.4
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• pp.204-208
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• 2000

Little information is available for the temporal variation in air temperature profile within rice canopies under development, while much works have been done for a fully developed canopy. Fine wire thermocouples of 0.003 mm diameter (chromel-constantan) were installed at 10 vertical heights by a 10 cm step in a paddy rice field to monitor the air temperatures over and within the developing rice canopy from one month after transplanting (June 29) to just before heading (August 24). According to a preliminary analysis of the data, we found neither the daytime temperature maximum nor the night time minimum at the active radiation surface (the canopy height with maximum leafages) during this period, which is a typical profile of a fully developed canopy. Air temperature within the canopy never exceeded that above the canopy at 1.5 m height during the daytime. Temporal march of the within-canopy profile seemed to be controlled mainly by the ambient temperature above the canopy and the water temperature beneath the canopy, and to some extent by the solar altitude, resulting in alternating isothermal and inversion structures.

• Korean Journal of Agricultural and Forest Meteorology
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• v.19 no.4
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• pp.270-279
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• 2017

Regional assessment of crop productivity using a gridded simulation approach could aid policy making and crop management. Still, little effort has been made to develop the systems that allows gridded simulations of crop growth using ORYZA 2000 model, which has been used for predicting rice yield in Korea. The objectives of this study were to develop a series of data processing modules for creating input data files, running the crop model, and aggregating output files in a region of interest using gridded data files. These modules were implemented using C++ and R to make the best use of the features provided by these programming languages. In a case study, 13000 input files in a plain text format were prepared using daily gridded weather data that had spatial resolution of 1km and 12.5 km for the period of 2001-2010. Using the text files as inputs to ORYZA2000 model, crop yield simulations were performed for each grid cell using a scenario of crop management practices. After output files were created for grid cells that represent a paddy rice field in South Korea, each output file was aggregated into an output file in the netCDF format. It was found that the spatial pattern of crop yield was relatively similar to actual distribution of yields in Korea, although there were biases of crop yield depending on regions. It seemed that those differences resulted from uncertainties incurred in input data, e.g., transplanting date, cultivar in an area, as well as weather data. Our results indicated that a set of tools developed in this study would be useful for gridded simulation of different crop models. In the further study, it would be worthwhile to take into account compatibility to a modeling interface library for integrated simulation of an agricultural ecosystem.

• Korean Journal of Soil Science and Fertilizer
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• v.33 no.2
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• pp.114-120
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• 2000

The aim of this study was to investigate the effects of slow-released nitrogen fertilizer(SRNF) on the growth and yield of rice. SRNF produced from wasted paper was applied to a clay loam paddy field comparing to urea fertilized field and only P-and K-fertilized field. Some agronomic components like as growth development and yield component were observed and physico-chemical properties of the soils were analyzed. Plant height and tiller numbers per hill showed higher in rice plant treated with SRNF than in one treated with urea at the early grow stage whereas they appeared to be all much the same at the end of growth stage. While the chlorophyll content in SRNF-treated rice shoot was higher than in urea-treated one, the photosynthetic activity in urea-treated rice shoot was slightly higher than in SRNF-treated rice. In harvested grain, the nitrogen content was higher than in SRNF treated rice than in urea treated rice, but in straws the content was less. At the harvesting stage, nitrogen uptake in grains was about 4% higher in SRNF-treated rice than in urea treated rice whereas in straws rather 20% lower. The N efficiency in SRNF treated rice was lower than in urea treated rice. In the soils treated with SRNF, pH, organic matter and phosphorus were higher than in the soils treated with urea. Total N content in SRNF treated soil was lower after experiment than in urea treated soil.

• Korean Journal of Weed Science
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• v.31 no.4
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• pp.375-383
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• 2011

This experiment was carried out to confirm characteristics of macro granule (GG) for herbicidal efficacy by using remote-controlled aerial application (RCAA) to control annual and perennial weeds in rice paddy field, and phytotoxicity to rice and non target plants of formulation types. Herbicidal efficacy of GG applied by using RCAA was 93.6~96.6% in flooded direct sowing cultivation. There was no difference in phytotoxicity between the hand and the power applicator methods in terms of height, number of tiller and yield component. Herbicidal efficacy of GG applied by using RCAA was 92.7~97.3% in machine transplanting rice field. There was no difference in phytotoxicity between the hand and RCAA methods in terms of height, number of tiller and yield component. When suspension concentrate (SC) and GG were applied directly on Chinese cabbage, lettuce, cucumber, pepper, soybean and wild sesame, several symptoms of injury such as, the inhibition of growth, yellowish, leaf fall and withering was observed.

• Korean Journal of Organic Agriculture
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• v.25 no.1
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• pp.203-218
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• 2017

The study was initiated at three rice paddy fields of each large-scale area environment-friendly agricultural district, Suncheon and Jangheung in Jeollanam-do, and Okcheon in Chungcheongbuk-do in 2016 to observe growth and nutrients in soil and rice in a season. Jangheung farm had two observed plots; conventional plots and conventional plots additionally fertilizing of 20% T-N with oil-cake. Soil pH, EC, and K concentration on June in Jangheung farm were significantly higher than those values observed in Suncheon and Okcheon farms. Annual rice T-N contents in the Jangheung farm were more than 80 g but decreased in a season. T-N concentration in rice was high in Jangheung farm but the concentrations of P and K were not significantly different among the three farms at harvest. Plant height was as low as 101 cm in Sunchon farm but high in the dry weight (72 g). Leaf SPAD was higher in Jangheung farm than those of other farms. Okcheon farm, with early cultivar 'Milky queen', produced high head rice of 93%, and high unhulled rice and the brown rice per ha. Therefore, the annual production income was as high as 26.7 million won per ha. However, nutrient (T-N + P + K) balance in Okcheon farm with high amount of fertilizer application were as high as 900 kg per ha. On the other hand, nutrient balance in Jangheung farm resulted in less than 300 kg.

• Current Research on Agriculture and Life Sciences
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• v.5
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• pp.59-67
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• 1987

The pot experiment was conducted using soils with varying contents of available phosphorus to select the reasonable method for determination of the available phosphorus content in soils for Nak-Dong rice cultivation. On a basis of the responses to the phosphorus tertilizer applied, the linear correlation coefficients by Bray No.1, Bray No.2, Lancaster, North Carolina and Olsen methods were 0.887, 0.868, 0.879, 0.952 and 0.911 for Nak-Dong rice yield, respectively. Of the methods tested, North Carolina method was the most suitable for determining, the phosphorus content in soils for Nak-Dong rice. The phosphorus application promoted the growth of Nak-Dong rice in pots for culm, tiller number, available stem and grain number per ear. Based on this experiment it could be presumed that the recommanded quantity of phosphorus fertilizer should attain to 5kg per 10a to promote the growth of Nak-Dong rice in A-soil and 10kg per 10a in B -, C - and D-soil. The results from the pot experiment will be somewhat different from those from the field experiment. Therefore, field experiment should be carried out for further information.