ANTICIPATION OF SUNFLOWER HARVEST THROUGH DESICCATION WITH HERBICIDES

Sunflower desiccation at the stage of physiological maturity allows ha rvesting anticipation. However, correct identification of this period is difficult and rises a question about desiccation effects on agronom ic and physiological characteristics when performed before that stage. To answer this question, a field experiment was conducted during 1990 /91 growing season at Estacao Experimental Agronomica of Universidade Federal do Rio Grande do Sul, RS, Brazil. Treatments tested were diqua t rates of 300, 400, and 800 g/ha; glyphosate at 900 g/ha, and a contr ol without chemical. The herbicides were sprayed 20 and 30 days after anthesis (DAA), corresponding to complete anthesis (R7) and physiologi cal maturity (R9), respectively. Sunflower desiccation with diquat bef ore physiological maturity reduced achene dry matter accumulation and oil content, this way diminishing achene and oil yields. Desiccation w ith diquat at physiological maturity did not affect these variables an d allowed a 7-day anticipation of sunflower harvest. Glyphosate applic ation, in either stage, did not affect achene dry matter accumulation; however, no harvesting anticipation was obtained with use of this pro duct.