Efficacy of Preemergence Propisochlor in Shallot

Abstract

The study of the efficacy of preemergence herbicide propisochlor (2-chloro-N- (isopropoxy methyl-N (2-ethyl-6-methylphenyl)-acetamide) for weed control in shallot was conducted at Chiang Mai University and Banhong, Lumpun Province during August-December 1997. The herbicides were treated as preemergence to weed and shallot with knapsack sprayer, flat fan nozzle, in the spray volume of 80 1/rai. At 1 day after application, rice straw was covered the soil for moisture conservation. It was indicated that annual grass weeds such as Eleusine indica (L.)Gaerth., Digitaria adscendense H.B.K.Henr, Echinochloa colona (L.)Link and annual broadleaf weeds such as Ageratum conyzoides Linn. Cleome viscosa Linn. and Amaranthus spinosus Linn. were controlled very effectively by propisochlor applied at the rates more than 230.4 g ai/rai. The use of propisochlor as preemergence to crop at the rates 115.2 up to 345.6 g ai/rai showed no phytotoxicity symptom in shallot. The application of propisochlor for preemergence weed control could increase shallot yield up to 210-381% compared to non weeding plot.