Reduction of Helminthosporium leaf spot iisease by soil amendments in the rice paddy field of Korea

摘要

In general, the contents of K_2O, CaO, Mn_2O_3 and particularly SiO_2 were very low in paddy field infected by Helminthosporium Leaf Spot Disease compared to the normal and the highly productive paddy fields. Especially high content of SiO_2 was noticeable in the highly productive paddy field. This study was carried out to reduce the Helminthosporium leaf spot disease by the soil amendments in rice. Whayeoungbyeo, very susceptible variety, was transplanted and four treatments of soil amendment application, control, lime (LR), Si (SiR) and two-times Si requirement (2SiR) treatments were used in the north area of Gyeongbuk province, Korea from 2002 to 2003. Comparing the contents of soil elements between before and after experiment, it was clarified that the contents of inorganic elements such as K, Ca, Mg and available SiO_2 were significantly increased in LR, SiR and 2SiR. Especially the available SiO_2 contents of rice plants were highly increased as well as that of soil in SiR and 2SiR. From these results of inorganic elements, the infection of the Helminthosporium leaf spot disease was significantly decreased by Si treatments. The rates of damaged leaf area were 16.5, 40.5, 65.8 and 73.2% in 2SiR, SiR, LR and control. The decreased damage by Si treatments increased the rate of ripened grains by 23% and also the grain yield by 21% compared to control. In grain quality, as the damage was severer, the rates of broken and white-belly grains were increased, thus the rate of head rice was decreased. The high rate of head rice and low content of protein in rice grains by Si treatments resulted in high palatability.