In lab studies, we compared the weed suppression abilities of 3 rice varieties [cv. Koukishumuchi (allelopathic), cv. Dongjinbyeo (non-allelopathic) and cv. K21 (newly bred potent allelopathic)] on barnyardgrass and thereby to reduce the herbicide rates. Kouketsumochi variety caused maximum weed suppression, while, Dongjinbyeo was least effective. The allelopathic suppression effects of Koukishumuchi, K21 and Dongjinbyeo on barnyardgras height were 45%, 31% and 20%, and on fresh weight 35%, 30% and 20%, respectively. These effects were converted into herbicide rate as per equation of toxicity regression. To inhibit the plant height and fresh weight, the toxicity regression values of Kouketsumochi were 10.6 mg/L and 8.4 mg/L, K21 (6.3 mg/L and 6.9 mg/L) and Dongjinbyeo (3.7 mg/L and 4.0 mg/L) respectively. By comparing the LD50 value with no rice, herbicide rate was reduced by 18–48%; with rice Kouketsumochi and K21, reduced the herbicide rates by 36% and 17%, respectively than Dongjinbyeo. Thus, the rice cultivars with allelopathic potential reduced the herbicide dose for weed management and promoting an eco-friendly rice cropping system.
Barnyardgrass, herbicide rates, rice allelopathy, rice varieties, weed suppression
