• KOREAN JOURNAL OF CROP SCIENCE
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• v.36 no.5
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• pp.407-428
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• 1991

The eastern coastal area having variability of climate is located within Taebaek mountain range and the east coast of Korea. It is therefore ease to cause the wind damages in paddy field during rice growing season. The wind damages to rice plant in this area were mainly caused by the Fohn wind (dry and hot wind) blowing over the Taebaek mountain range and the cold humid wind from the coast. The dry wind cause such as the white head, broken leaves, cut-leaves, dried leaves, shattering of grain, glume discolouration and lodging, On the other hand the cold humid wind derived from Ootsuku air mass in summer cause such symptom as the poor rice growth, degeneration of rachis brenches and poor ripening. To minimize the wind damages and utilize as a preparatory data for wind injury of rice in future, several experiments such as the selection of wind resistant variety to wind damage, determination of optimum transplanting date, improvement of fertilizer application methods, improvement of soils and effect of wind break net were carried out for 8 years from 1982 to 1989 in the eastern coastal area. The results obtained are summarized as follows. 1. According to available statisical data from Korean meteorological services (1954-1989) it is apperent that cold humid winds frequently cause damage to rice fields from August 10th to September 10th, it is therefore advisable to plan rice cultivation in such a way that the heading date should not be later than August 10th. 2. During the rice production season, two winds cause severe damage to the rice fields in eastern coastal area of Korea. One is the Fohn winds blowing over the Taebaek mountain range and the other is the cold humid wind form the coast. The frequency of occurrence of each wind was 25%. 3. To avoid damage caused by typhoon winds three different varieties of rice were planted at various areas. 4. In the eastern coastal area of Korea, the optimum ripening temperature for rice was about 22.2$^{\circ}C$ and the optimum heading date wad August 10th. The optimum transplanting time for the earily maturity variety was June 10th., medium maturity variety was May 20th and that of late maturity was May 10th by means of growing days degree (GDD) from transplanting date to heading date. 5.38% of this coastal area is sandy loamy soil while 28% is high humus soil. These soil types are very poor for rice cultivation. In this coastal area, the water table is high, the drainage is poor and the water temperature is low. The low water temperature makes it difficult for urea to dissolve, as a result rice growth was delayed, and the rice plant became sterile. But over application of urea resulted in blast disease in rice plants. It is therefore advise that Ammonium sulphate is used in this area instead of urea. 6. The low temperature of the soil inhibits activities of microorganism for phosphorus utilization so the rice plant could not easily absorb the phosphorus in the soil. Therefore phosphorus should be applied in splits from transplanting to panicle initiation rather than based application. 7. Wind damage was severe in the sandy loamy soil as compared to clay soils. With the application of silicate. compost and soil from mointain area. the sand loamy soil was improved for rice grain colour and ripening. 8. The use of wind break nets created a mocro-climate such as increased air. soil and water temperature as well as the reduction of wind velocity by 30%. This hastened rice growth, reduced white head and glume discolouration. improved rice quality and increased yield. 9. Two meter high wind break net was used around the rice experimental fields and the top of it. The material was polyethylene sheets. The optimum spacing was 0.5Cm x 0.5Cm. and that of setting up the wind break net was before panicle initiation. With this set up, the field was avoided off th cold humid wind and the Fohn. The yield in the treatment was 20% higher than the control. 10. After typhoon, paddy field was irrigated deeply and water was sprayed to reduce white head, glume discolouration, so rice yield was increased because of increasing ripening ratio and 1, 000 grain weight.

• Korean Journal of Soil Science and Fertilizer
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• v.9 no.4
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• pp.235-244
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• 1976

Following results are obtained by re-evaluating N. P. K. and soil improvement trials conducted from 1964 to 1969 in valley paddy soils in rolling lands (Jisan-series, imperfectly drained and Yongji-series, moderately well drained). 1. Average grain yield of rice in no fertilizer plots and the highest yield plots for Yongji-series (31 experiments) were 319 and 507kg/10a respectively, and that of Jisan-series (15 experiments) were 396 and 567kg/10a respectively. The fertility difference between two series may have been a result of the cultivation history. Jisan-series is a mature soil which has a long cultivation history and Yongji-series is sub-mature soil 2. Soil chemical characteristics for Jisan-series are charaterized by 12.8meq/100g in CEC, 6.5meq/100g in exchangeable Ca, 3.9% in OM, and 64 ppm in available $P_2O_5$ For Yongji-series they were 10.4meq/100g in CEC, 4.7meq/100g in exchangeable Ca, 3.2% in OM and 103ppm in available $P_2O_5$. 3. Deep plowing and application of organic matter and lime are expected to be effective in increasing fertility level of soils of Yongji-series. The same will be effective in some soils of Jisan series where the fertility level is low. 4. Jisan-series shows high response to nitrogen, while Yongji series shows sharp decrease in rice yield at the high levels of nitrogen. Both series, however, showed high response to nitrogen only when the OM level was higher than 3%. 5. The optimum level of nitrogen was 8~9kg for Jisan-series, and 10~11kg/10a for Yongji-series. The yield increase per kg of applied nitrogen was 12kg for Jisan-series and 13kg for Yongji series. 6. The optimum level of phosphorus at the optimum level of nitrogen was 6kg/10a for Yongji-series and 3kg/10a for Jisan-series. The optimum level of phosphorus, however, was different depending upon the nitrogen level. It was assumed that Yongji-series required more fertilizer (available $P_2O_5$ was 110ppm) than Jisan-series (available $P_2O_5$ was 64ppm) because the availability of P was higher in Jisan-series than Yongji-series due to the severe reduction of Jisan-series. 7. The response of potassium was also depending upon the nitrogen level. In Yongji-series the potassium response at 8kg/10a nitrogen level decreased with increasing levels of potassium, but the higher level of introgen, potassium response was also higher. In Jisan-series potassium response was recognized at all nitrogen levels. The optimum level of potassium at the optimum level of nitrogen was 8kg/10a in both serieses. 8. The reasonable ratio of NPK fertilizer seems to be 1:0.6:0.6:for Yongji-series and 1:0.4:1 for Jisan-series as N:$P_2O_5$:K.