Thesis Abstract of AGS Students

Pornpun Suttireangwong (1988)

The study aimed to verify "improved" technology at farm level in the Chiang Mai Valley. A case of chemical technology for weed control in soybean after rice system was chosen to be verified at three districts. The preliminary study indicated that farmers prefered chemical weed control to conventional hand weeding. However the weed control techniques such as dosage and time of application were inappropriate.

The field experiment was conducted in 1986 to compare the different methods of weed control in soybean. The design of experiment was randomized completed block with 5 treatments. The experimental sites were located within the boundary of the lateral canal No.6 in the Mae Taeng Irrigation Project.

All the weed control treatments showed significant reduction in weed population especially family Gramineae. The application of alachlor followed by fluazifob butyl gave the most satisfactory results. Hand weeding was effective at the early stage of soybean growth but recovery of weeds was evident at later stages.

The combined application of alachlor with fluazifob butyl and hand weeding gave the similar results of dry matter yields in soybean throughout the growing season. Dry matter yields were higher in these treatments than those of paraquat and glyphosate treatments. However, there were no statistically significant differences between the weed control treatments, giving an average in seed yield of 217 kg/rai. When weed control was absent, yield of soybean declined to 189 kg/rai.

The benefit cost ratio (B/C) was also computed to make a comparison between different weed control methods. The highest value of 2.39 was found in the paraquat treatment. In contrast, alachlor followed by fluazifob butyl and hand weeding gave negative return with the B/C ratio of 0.86, 0.97 respectively.

The study of farmers' attitude towards chemical weed control indicated that all respondants prefered chemicals to hand weeding. Reduction in labour utilization was the dominant factor in deciding to use chemicals. In the study village, it was also observed that, there would be a strong tendency to use chemical weed control. The farmers obtained information on chemical weed control mainly from the sub-district agricultural extension officer (Kaset Tambon), sale representatives and their neighbours.

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