Nitrogen rates and side-dress timing on two sunflower cultivars

Abstract

Three nitrogen rates (40, 80, and 120 kg/ha) applied at three growth stages corresponding to 20, 35 and 50 days after emergence, were tested on two sunflower cultivars (DK 180 and Contisol 711) at Eldorado do Sul, RS, Brazil, during 1987/88. Timing of N side-dressing did not affect grain yield although some variation in yield components were observed. Achenes per capitulum were higher at early N aplications. Achene weight had little change, with some increase at later application (DK 180). Grain yield increased with N rate mainly due to achene number (both cultivars) and achene weight (DK 180). Oil yield was affected by grain yield and by oil content. Oil content decreased as more nitrogen was available (Contisol 711) and by delayed N application.