• KOREAN JOURNAL OF CROP SCIENCE
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• v.26 no.1
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• pp.1-31
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• 1981

Experiments were conducted to investigate rice varietal response to low water and air temperatures at different growth stages from 1975 to 1980 in a phytotron in Suweon and in a cold water nursery in Chooncheon. Germination ability, seedling growth, sterility of laspikelets, panicle exertion, discoloration of leaves, and delay of heading of recently developed indica/japonica cross(I/J), japonica, and indica varieties at low air temperature or cold water were compared to those at normal temperature or natural conditions. The results are summarized as follows: 1. Practically acceptable germination rate of 70% was obtained in 10 days after initiation of germination test at 15\circ_C for japonica varieties, but 15 days for IxJ varieties. Varietal differences in germination ability at suboptimal temperature was greatest at 16\circ_C for 6 days. 2. Cold injury of rice seedlings was most severe at the 3.0-and 3.5-leaf stage and it was reduced as growth stage advanced. A significant positive correlation was observed between cold injury at 3-leaf stage and 6-leaf stage. 3. At day/night temperatures of 15/10\circ_C seedlings of both japonica and I/J varieties were dead in 42 days. At 20/15\circ_C japonica varieties produced tillers actively, but tillering of I/J varieties was retarded a little. At 25/15\circ_C, both japonica and I/J varieties produced tillers most actively. Increase in plant height was proportional to the increase in all varieties. 4. In I/J varieties the number of differentiated panicle rachis branches and spikelets was reduced at a day-night temperature of 20-15\circ_C compared to 25-20 or 30-25\circ_C, but not in japonica varieties although panicle exertion was retarded at 20-15\circ_C. The number of spikelets was not correlated with the number of primary rachis branches, but positively correlated with that of secondary rachis branches. 5. Heading of rice varieties treated with 15\circ_C air temperature at meiotic stage was delayed compared to that at tillering stage by 1-3 days and heading was delayed as duration of low temperature treatment increased. 6. At cold water treatment of 17\circ_C from tillering to heading stage, heading of japonica, I/J, and cold tolerant indica varieties was delayed 2-6, 3-9, and 4-5 days, respectively, Growth stage sensitive to delay of heading delay at water treatment were tillering stage, meiotic stage, and booting tage in that order, delay of heading was greater in indica corssed japonica(Suweon 264), japonica(Suweon 235), and cold tolerant indica(Lengkwang) varieties in that order. Delay of heading due to cold water treatment was positively correlated with culm length reduction and spikelet sterility. 7. Elongation of culms and exertion of panicles of rice varieties treated with low air temperature 17\circ_C. Culm length reduction rate of tall varieties was lower than that of short statured varieties at low temperature. Panicle exertion was most severaly retarded with low temperature treatment at heading stage. Generally, retardation of panicle exertion of 1/1 varieties was more severe than that of japonica varieties at low temperature. There was a positive correlation between panicle exertion and culm length at low temperature. 8. The number of panicles was increased with cold water treatment at tillering stage, but reduced at meiotic stage. As time of cold water treatment was conducted at earlier growth stage, culm length was shorter and panicle exertion poorer. 9. Sterility of all rice varieties was negligible at 17\circ_C for three days but 30.3-85.2% of strility was observed for nine-day treatment at 17\circ_C. Among the tested varieties, sterility of Suweon 264 and Milyang 42 was highest and that of Suweon 290 and Suweon 287 was lowest. The most sensitive growth stage to low temperature induced sterility was from 15 to 5 days before heading. There was positive correlation between sterility of rice plants treated with low temperature at meiotic and heading stage. 10. Percentage of spikelet sterility was greatest at cold water treatment at meiotic stage (auricle distance -15～-10cm) and it was higher in 1/1 (Suweon 264, Joseng tongil), japonica (Nongbaek, Towada), and cold tolerance indica(Lengkwang) varieties in the order. Level of cold water and position of young-ear affected on the sterility of varieties at meiotic stage; percentage of spikelet sterility of variety, Lengkwang, of which young-ear was located above the cold water level was high, but that of short statured variety, Suweon 264, of which young-ear was located in the cold water was lower. 11. Percentage of ripened grains was not reducted at 15\circ_C air temperature for three days at full heading stage in all varieties. However, at six-day low temperature treatment Suweon 287, Suweon 264 showed percentage of ripended grains lower than 60%, but at nine-day low temperature treatment all varieties showed percentage of ripened grains lower than 60%. Low temperature treatment of 17\circ_C from 10 days after heading for 20 days did not affect on the ripening of all varieties. 12. Uptake of nitrogen, phosphorous, potassium, calcium, and magnesium in whole plants was higher at average air temperature of 25\circ_C, but concentration of the elements was lower compared to those at 19\circ_C. However, both total uptake and concentration of manganese were higher at 19\circ_C compared to 25\circ_C. 13. Higher application of nitrogen, phosphorus, silicate, and compost increased yield of rice due to increased number of panicles and spike let fertility in cold water irrigated paddy.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.53 no.spc
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• pp.31-36
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• 2008

This study was carried out to clarify the effect of silicate application on rice grain quality and storage characteristics in Ilpumbyeo cultivar. In yield and yield components, panicles and spikelet numbers were increased and ripened grain rate was also increased by 2%. Head rice yield was increased by $7.7{\sim}9.5%$ in silicate application. Protein content of milled rice was reduced by $0.2{\sim}0.3%$ and head rice rate was increased by $2.9{\sim}6.7%$ in silicate application due to decrease of chalky and damaged rice rate. In milling characteristics, color separation rate was improved by $4.2{\sim}7.2%$ and colored rice rate was decreased by $5.5{\sim}16.6%$ in silicate application. Acid value of stored brown rice were increased slowly in low temperature and silicate application, but that in room temperature and no silicate application was increased remarkably. The best degree rate of stored brown rice (over than 7.5 of pH) measured by the pH of grain was increased by the silicate application in both low and room temperature. Therefore, it was suggested that the storage characteristics of rice grain was improved by the silicate application.

• Korean Journal of Soil Science and Fertilizer
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• v.7 no.1
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• pp.35-42
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• 1974

From the results of countrywide two year N. P. K simple trial with newly bred IR 667-Suwon 214 and leading local varieties for comparison soil productivity (yield without fertilizer) and fertilization productivity (yield increase with fertilizer) were investigated. 1. IR667 showed higher yield than leading local by 19% in 1971 and by 12% in the year of low temperature stress, 1972. High yielding capacity of IR667 was attributed to greater number of spikelet per panicle. The coefficient of variation in yield was smaller in IR667 but the leading locals showed higher yield in 23(1971) and 30% (1972) of the fields. 2. IR667 required more nitrogen, especially phosphorus and potassium. Fertilization efficiency (yield increment per unit fertilizer) in IR667 was-about 4kg higher in nitrogen but smaller in phosphorus and almost the same in potassium. 3. Soil productivity was higher in IR667 but percent contribution of soil productivity to total productivity (field productivity) was lower. 4. Percent contribution of fertilization productivity to field productivity was 19 to 33, of which 5 was due to phosphorus and potassium. 5. The greater the soil productivity, the greater the field productivity becomes, but the much greater the percentage contribution of soil productivity becomes. 6. Fertility saturation point at which fertilization efficiency is nil, was propoesd as a soil productivity (or field productivity) limit.

• Korean Journal of Soil Science and Fertilizer
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• v.39 no.4
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• pp.209-213
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• 2006

This study was carried out to investigate the changes in soil chemical properties and yields of crops by rice-soybean rotation cropping system at silt loam soil. There were 4 rotation cropping systems; continuous rice cultivation, annual, biennial and triennial rotation of soybean and rice. There were little change in pH, organic matter, $Ca^{2+}$ and $K^+$ contents with decrease in available phosphate content in the continuous rice cropping. The cropping system of soybean-rice caused to increase in available $P_2O_5$, $K^+$ and $Ca^{2+}$ in the soil after harvest. Content of $NH_4-N$ in the soil also increased after the rotation of soybean than the continuous rice cropping in the soil during the rice growth period. These chemical change in the soil caused to increase rice growth in number of the panicles and the spikelet per square meter. The yield of rice was increased by the rotation with soybean, and was gradually increased in the triennial rotation of soybean and rice. But the yield of soybean was decreased in continuous cultivation for two or three years in the paddy field. It was recommended for annual rotation to prevent the yield of soybean from decrease.

• Korean Journal of Remote Sensing
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• v.33 no.5_2
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• pp.733-740
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• 2017

This review introduces the empirical approach of rice yield forecasting and compares it with remote sensing approach. The empirical approach, was based on the results of the rice growth and yield monitoring experiment in 17 sites, estimated rice yield by recombination of yield components. The number of spikelet per unit area was from results of experiment sites and grain filling rate was estimated from linear regression with sunshine hours. The estimation results were relatively accurate from 2010 to 2016. The smallest error was 1 kg / 10a and the largest error was 19 kg / 10a. The largest error was caused by the typhoon. The empirical approach did not fully reflect the spatial variation caused by disasters such as typhoon or pest. On the other hand, remote sensing could explain spatial variation caused by disasters. Therefore, if there are not any disaster in rice field, both approaches are valid and remote sensing will be more accurate when any local disaster occurs.

• Korean Journal of Agricultural and Forest Meteorology
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• v.20 no.1
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• pp.135-143
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• 2018

The effect of elevated temperature on temperate paddy rice will be significant for dependable food supply in East Asia. Using temperature gradient field chamber (TGFC), which was designed to make the horizontal air temperature gradient by $0^{\circ}C$ to $3^{\circ}C$ higher than outside, we examined the measurement to understand the effects of extremely high temperature on paddy rice. In particular, the data of the year 2016, the worst heat wave in over 22 years, was analyzed in this study. The rice height in the relatively warmed condition was rapidly increased during early growth stage. However, the average grain weight and number of spikelet per panicle in the warmed chamber condition were gradually declined with increasing air temperature averaged for 40 days after first heading in each chamber. In particular, the grain yield was more dramatically decreased by the raising temperature because the percent ripened grain was quickly dropped as getting over the threshold temperature for pollination. Therefore, the surplus photosynthetic product by such lower grain filling rate may disturbed the decreases of the NDVI (Normalized Difference Vegetation Index) and SPAD chlorophyll values after first (normal) heading. In addition, the late-emerging head grain were appeared. However, this yield was too small to recover the normal yields decreased by extremely high temperature condition. Our result represented that the warmed condition in 2016 would be the critical limit for the stable yield of temperate paddy rice.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.40 no.1
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• pp.103-112
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• 1995

Six African rice varieties, two each from three types having the characteristics of partially, irregularly, and completely developed abscission layers, were selected and grown 1） to investi-gate the histological differences during the formation and development of the abscission layers and 2） to evaluate the changes in the breaking tensile strength required to detach a grain from its pedicel dur-ing ripening period in relation with developmental stage of the abscission layers. In African rice, the panicle and spikelet grew rapidly from 15 days before heading and almost completely grown in length at five days before heading. The abscission regions were recognized at 15 days before heading. However, any apparently developed abscission layers were not recognized in the lemma side for partially developed abscission layers. A group of parenchymatous cells could be observed sporadically in the abscission layers of the lemma side for irregularly developed ab-scission layers. At ten days before heading, abscission layers consisting of one or two layers of parenchymatous cells were clearly distinguished from neighboring cells due to thickened and lignified cell walls. There were a number of individual parenchymatous cells scattered sporadically in the lemma side of partially developed abscission layers, and a number of grouped parenchymatous cells scattered randomly in the lemma side of irregularly developed abscission layers. At two weeks after heading, the grains became almost fully filled. The cracking of abscission layers between rachilla and pedicel was observed, and the breaking tensile strength required to detach a grain from its pedicel was as low as that at harvest time.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.48 no.6
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• pp.516-526
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• 2003

Thirty-six barley varieties including Korean modern and local varieties were tested for drought-tolerance in the field of plastic rain shelter, Drought treatment was initiated at initial tillering stage (March 27, 2002) by withholding irrigation and lasted until harvest. Soil water potential maintained at around -0.05㎫ in the control plot and varied from -0.05㎫ (at the initial stage of drought treatment) to -0.29㎫ in the drought treatment plot. At forty days after drought treatment, relative water content (RWC), osmotic potential (OP), osmotic adjustment (OA), and $^{13}\textrm{C}$ discrimination ($\Delta$) were measured and then plants were sampled for leaf area index (LAI) and dry weight (DW). Barley was harvested at maturity for determining DW, grain yield, 1000 grains weight and number of spikelet. The tested varieties revealed wide spectrum of drought tolerance. Dongbori-1, Chalbori, Changyeongjaerae, Samdobori and Weolseong 87-31 showed strong drought-tolerance while Songhagbori and Suwonmaeg360 showed weak drought-tolerance. The drought injury indexes (drought/control ratio) of DW and yield revealed significant positive correlation with leaf RWC in drought treatment plot and $\Delta$ in the control plot, but obvious negative correlation with leaf OP and OA under drought condition. In addition, all the drought indexes of OP, $\Delta$ and RWC showed obvious positive correlation with the drought injury indexes of DW, 1000 grain weight and yield. Thus, OP and RWC under drought condition and $\Delta$ under well-watered condition would be used as the evaluation criteria for drought- tolerance of barley genotypes. However, further investigation is needed for the relationship between $\Delta$ and drought-tolerance as the other reports were not consistent with our result.

• Korean Journal of Environmental Agriculture
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• v.20 no.4
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• pp.232-237
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• 2001

This study was conducted to clarify the effects of physical stimulation to the rice plant by free-ranging ducks (Chinese native ducks) on growth, lodging resistance and yield of the rice plants in a rice-duck farming system. Two paddy fields were used for this experiment, one exposed to physical stimulation (PS) and the other with no physical stimulation (NPS). Fifteen days after ducks were introduced into the paddy plot, rice plants in the PS field were significantly (P<0.05) shorter than those in the NPS field. Measurements of lodging characteristics showed that, the 3rd internode was significantly (P<0.05) shorter in the PS treatment than in the NPS treatment, but neither the 4th internode length nor the center of gravity of the rice plants differed between treatments. The breaking strength of $N_4$ in PS rice was significantly (P<0.05) higher than in NPS rice, however the bending moment and the lodging index of $N_3$ (distance between fulcra - 5 cm) was significantly (P<0.05) lower in PS than in NPS. The number of panicles per $m^2$ was significantly (P<0.05) greater in PS rice than in NPS, but there was no such difference in spikelet number per panicle, percentage of ripened grain or weight per 1000 kernels. Paddy rice yield per $m^2$ in the PS treatment was significantly (P<0.05) higher than that in the NPS treatment.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.35 no.3
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• pp.239-247
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• 1990

In order to investigate the degree of grain shedding of red rices collected in Korea, breaking tensile and breaking bending strengths of 269 varieties; 82 Korean and 100 foreign red rices and 87 Korean cultivars including 26 native varieties, 30 Japonica-Indica hybrids and 31 Japonica type varieties, were measured at harvest time. Also, histological characteristics of abscission region between spikelet and pedicel were observed. The breaking tensile and breaking bending strengths of both Korean and foreign red rices were weaker than those of Japonica-Indica hybrids which were known as easily shedding varieties in Korea. Abscission layers were observed in the majority of Korean red rices except for 5 varieties, and those of all varieties belonging to both long grain types and 'Sare's were cracked completely at harvest time, while those of round grain types were not cracked except one variety. The breaking tensile and breaking bending strengths of the tested varieties having cracked abscission layer were weaker than those of non-cracked ones. Both strengths of breaking tensile and breaking bending were positively correlated with diameter of supporting zone and thickness of sclerenchyma tissue surrounding central vascular tissue of suporting zone at 0.1% significant level, respectively.