Economic Threshold Levels Based on Rice Yield and Rice Quality as Affected by Densities of Scirpus planiculmis in Transplanting Rice Cultivation
2008
Kwon, O.D. (Jeonnam Agricultural Research and Extension Service, Naju, Republic of Korea) | Kuk, Y.I. (Sunchon National University, Sunchon, Republic of Korea), E-mail: [email protected] | Moon, B.C. (National Institute of Agricultural Science and Technology, RDA, Suwon, Republic of Korea)
This study was conducted to develop predication model systems for reduction in rice yield and rice quality as affected by densities of Echinochloa crus-galli and Scirpus planiculmis in transplanted rice cultivation and to determine economic threshold levels of weeds. Plant height (cm) and number of branch at 15-18 days after transplanting of tuber of S. planiculmis were 38.8-44.1 and 2.7-3.2, respectively. In transplanted rice cultivation, yield of rice in densities of E. crus-galli (96 per ㎡) and S. planiculmis (96 per ㎡) was reduced by 35.7 and 28.6%, respectively. Head rice was obviously reduced by increasing occurrence densities of E. crus-galli and S. planiculmis, whereas cracked rice was increased with increasing occurrence densities of E. crus-galli and S. planiculmis. However, there were no significant differences in other rice quality such as protein and quality value as affected by densities of E. crus-galli and S. planiculmis. Regression equations for prediction models of rice yields loss on densities of E. crus-galli and S. planiculmis were Y=549.4/(1+0.006110x), r²=0.928 and Y=534.6/(1+0.004537x), r²=0.760, respectively. The competitiveness of E. crus-galli was 1.4-fold higher than that of S. planiculmis. Economic threshold densities of E. crus-galli and S. planiculmis were 3.4 and 4.6 per ㎡, respectively.
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