• KOREAN JOURNAL OF CROP SCIENCE
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• 제26권1호
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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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• 제3권
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• pp.49-82
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• 1965

For the stable and high yields of low-land rice in Korea, the characteristics of rice plant for the vegetative and physiological responses, plant type formation, and yield components have been studied in order to obtain the fundamental data for the improvement of cultural practices, especially for the ideal fertilizer application. Furthermore the environmental conditions in Korea including temperatures, light, precipitation, and soil conditions have been compared in the broad sense with those in Japan, and the application of nitrogen, phosphorus, potassium, silicate and other micro-nutrients were described in relation to the characteristics of environmental conditions for the improvement of fertilizer application. 1. The average yield of polished-rice per 10 are in Korea is about 204 kg and this values are much less than those in Japan and Taiwan where they produce 77% to 13% more than in Korea. The rate of yield increase a year in Korea is 4.2 kg, but in Japan and Taiwan the rates of yield increase a year are 81 % and 62%, respectively. It was also found that the coefficient of variation of yield is 7.7% in Korea, 6.7% in Japan and 2.5% in Taiwan. This means that the stability of producing rice in Korea is very low when compared with those in Japan and Taiwan. 2. It was learned from the results obtained from the 'annual yield estimation experiment' that there are big differences in the respect of plant type formations between rice crops grown in Japan and Korea. The important differences found were as follows: (1) The numbers of spikelets per 3.3 square meters are 891 in Korea and 1, 007 in Japan(13% more than in Korea). (2) The numbers of tillers per 3.3 square meters at the stage of maximum tillering are 1, 150 in Korea, but in Japan they showed 19% more than in Korea. (3) The ratio of effective tillers to total tillers is 77.5% in Korea and 74.7% in Japan, which seems to be higher in Korea than in Japan. But the ratio in Korea is very low when considered the numbers of total tillers in both countries. (4) The ratio of grain to straw is 85.4% in Korea and 96.3% in Japan. 3. The average temperatures during the growing season at the area of Suwon, Kwangjoo and Taegu are almost same as those in the district of Jookokoo(Fookoo yama) in Japan, i.e., the temperatures during the rice-growing season in Korea are similar to those in the southern-warm regions of Japan. 4. Considering the minimum temperatures at the stage of limiting transplanting, 13$^{\circ}C$, the time of transplanting might be 30 to 40 days earlier than presently practicing transplanting time, which comes around June 10. 5. The temperatures during the vegetative growth in Korea were higher than those temperatures that needed in the protein synthesis which ate the main metabolism during this stage. However, the temperatures at the time of reproductive growth was lower than the temperatures that needed in the sugar assimilation which is main metabolism in this stage. In this point of view, it might be considered that the proper time of growing rice plant in Korea would be rather earlier. 6. The temperatures and the day light conditions at the time of first tillering stage of rice plant, when planted as presenting transplanting practices, are very satisfactory, but the poor day light length, high temperatures and too wet conditions in the time of last-tillering stage(mid or last July) might cause the occurrence of disease such as blast. 7. The heading stage of rice plants at each region through nations when planted as presently practicing method comes when the day light length is short. 8. It was shown that the accumulated average air-temperature at the time of maturing stage was not enough and the heading time was too late, when considered the annual deviations of mean temperatures and low minimum temperatures. 9. The nitrogen content of each plant part at the each growing stage was very high at the stage of vegetative growth when compared with the nitrogen content at the stage of reproductive growth after heading. In this respect it was believed to be important to prevent the nutrient shortages at the reproductive stages, especially after the heading. 10. The area of unsatisfactory irrigation paddy fields and natural rain-fed paddy fields are getting reduced in Korea. The correlation between the rate of reducing unsatisfactory irrigation and natural rain-fed paddy fields and the rate of yield increase were computed. The correlation coefficients(r) between the area of unsatisfactory irrigation paddy fields and yield increase were +0.525, and between the natural rain-fed paddy fields and yield increase, +0.832 and between the unsatisfactory irrigation plus natural rain-fed paddy fields and yield increase, +0.84. And there were. highly significant positive correlations between natural rain-fed paddy fields and yield increases indicating that the less the area of natural rain-fed paddy fields, the greater the yields per unit area. 11. The results obtained from the fertilizer experiments (yield performance trials) conducted in both Korea and Japan showed that the yield of non-fertilized plots per 10 are was 231 kg in Korea and 360 kg in Japan. On the basis of this it might be concluded that the fertility of soil in Korea is lower than that in Japan. Furthermore it was. also found that the yields of non-nitrogen applied plots per 10 are were 236 kg in Korea and 383 kg in Japan. This also indicates that the yields of rice in Korea are largely depending on the nitrogen content in the soil. 12. The followings were obtained when the chemical natures of soils in both Korea and Japan were compared. (1) The content of organic matter, total nitrogen, exchangeable calcium, and magnesium in Korea were no more than the half those in Japan. (2) The content of N/2 chloride and soluble silicate in low-land soil were on the average lower in Korea. (3) The exchange capacity of bases in Korea was no more than half that in Japan. 13. It was also observed by comparing the soil nature of the soil with high yielding capacity with the soil with low yielding capacity that the exchange capacity of bases, exchangeable calcium and magnesium, potassium, phosphorus, manganese, silicate and iron were low in the soil with low yielding capacity. 14. The depth of furrow slice was always deeper in the soil with high yielding capacity, and the depth of furrow slice in Korea was also shallower than that in Japan. 15. Summarizing the various conditions mentioned previously and considering the effects of silicate and trace elements such as manganese and iron besides three elements on the physiological and plant type formation of rice crops, more realistic and more ideal fertilizing practices were proposed. proposed.