Effect of Glyphosate Herbicide Spraying Period on Growth and Yield of Cassava Variety Rayong 11

Abstract

The effect of glyphosate herbicide spraying period on growth and yield cassava variety Rayong 11.was studied at Ubon Ratchathani Field Craps Research Centre (UBFCRC) during 2008-2010. The experiment was designed as RCB with 4 replications and 7 treatments namely hand weeding at 1 and 2 months after germination, glyphosate were applied in the rate of 360 g (ai)/rai at 1 month, 1 and 2 months, 1 and 3 months, 2 months, 3 months, and control (non treated). The results showed that 2 times of glyphosate application at 1 and 2 months gave fresh yield (4,298 kg/rai) and dry yield (1,723 kg/rai) similar to hand weeding. Even the 2^nd application showed the higher toxicity level but it was harmless. Moreover, the application of glyphosate had given in an acceptable marginal rate of return (MRR) and twice times of applications (1 and 2 months) had the highest value of investment.