Anticipation of sunflower harvest through desiccation with herbicides

Abstract

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