Submitted to: Weed Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/1/2005
Publication Date: 9/1/2005
Citation: Estorninos, L.E., Gealy, D.R., Talbert, R.E., Gbur, E.E. 2005. Rice and red rice (Oryza sativa) interference: I. Response of red rice to sowing rates of tropical japonica and indica rice cultivars. Weed Science. 53:676-682. Interpretive Summary: Red rice is an aggressive competitor in the southern U.S. against commercial rice varieties such as Kaybonnet. Natural weed suppressive activity has recently been demonstrated in certain Asian indica semidwarf rice varieties including PI 312777 and Guichao. Field experiments were conducted at Stuttgart, AR to evaluate the growth response of red rice to different planting rates of Kaybonnet, PI 312777, and Guichao. The planting rates were zero (red rice only), half the normal rate, the normal rate, and double the normal rate. PI 312777 produced greater leaf area, more stems and panicles, and yielded more than Kaybonnet when grown with red rice. Likewise, Guichao and PI 312777 reduced red rice seed yields at least 10 and 20% more, respectively, than did Kaybonnet. Averaged over all rice varieties, even the half rate of planting reduced red rice seed yield by 71 and 36%, respectively in 1997 and 1998 when compared to red rice growing alone. The normal and double planting rates of rice reduced red rice yields even further. These results demonstrate that red rice was more competitive against the tropical japonica Kaybonnet, than the indica PI 312777. Despite a short stature, prolific stem production by PI 312777 apparently contributed greatly to its reduction of growth and productivity of red rice. Thus, high stem production capacity may be a useful trait for weed-suppressive rice varieties suitable in-low input cropping systems.
Technical Abstract: Field experiments were conducted at Stuttgart, AR, to evaluate the growth response of a local strawhull red rice to sowing densities of 0, 50, 100, and 150 kg ha-1 of Kaybonnet, Guichao, and PI 312777 rice cultivars. In both 1997 and 1998, PI 312777 produced greater leaf area, more tillers and panicles, and yielded more than Kaybonnet when grown with red rice. Likewise, red rice seed yields were 21 to 23% lower in PI 312777 plots and 12 to 14% lower in Guichao plots, than they were in Kaybonnet plots. Rice sowing rates of 50 kg ha-1 reduced red rice seed yield by 71 and 36%, respectively in 1997 and 1998 when compared to red rice in monoculture, and increased rice sowing rates further reduced red rice seed yields. These results demonstrate that red rice was more competitive against the tropical japonica Kaybonnet, than the indica PI 312777. Despite its semidwarf stature, PI 312777 manifested its naturally suppressive characteristic by producing more tillers. This attribute could be an important characteristic to consider in attempting to reduce herbicide inputs for weed control.