Effect of Densities of Echinochloa crus-galli and Cyperus difformis in Transplanting Rice Cultivation on Rice Yield and Rice Quality, and Economic Threshold Levels of the Weeds
2007
Kwon, O.D. (Jeonnam Agricultural Research and Extension Service, Naju, Republic of Korea) | Kuk, Y.I. (Chonnam National University, Gwangju, Republic of Korea), E-mail: [email protected] | Cho, S.H. (Jeonbuk Agricultural Research and Extension Services, Iksan, Republic of Korea) | Moon, B.C. (National Institute of Agricultural Science and Technology, RDA, Suwon, Republic of Korea)
This study was conducted to find the levels of reduction in rice yield and rice quality as affected by densities of Echinochloa crus-galli and Cyperus difformis in transplanted rice cultivation of two sites (Naju and Iksan) and to determine economic threshold levels of the weeds. The yield of rice in densities of E. crus-galli (96 per ㎡) and C. difformis (576 per ㎡) was reduced by 51~60 and 18~19%, respectively. Head rice was obviously reduced by increasing occurrence densities of E. crus-galli, and immature rice and damaged kernel were increased with increasing occurrence densities of E. crus-galli, whereas only immature rice was increased with increasing occurrence densities of C. difformis. However, there were no significant differences in other the rice quality such as protein and amylose as affected by densities of E. crus-galli and C. difformis. Regression equations for prediction models of rice yield loss on densities of E. crus-galli and C. difformis were Y=599.3/(1+0.10568X) r²=0.961, and Y=613.1/(1+0.000403), r²=0.857, respectively, in Naju, whereas, Y=544.7/(1+0.017220X) r²=0.953 and Y=556.5/(1+0.000730X) r²=0.854, respectively in Iksan. The competitiveness of E. crus-galli was 23.8~26.2-fold higher than that of C. difformis. Economic threshold densities of E. crus-galli and C. difformis calculated by Cousens' method (1985) were 0.8~1.1 and 27.8~28.8 per ㎡, respectively. This result means that yield of rice in transplanted rice cultivation can be reduced by more than the economic threshold densities of E. crus-galli and C. difformis.
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