Abstract

The genotype of sunflower (Helianthus annuus L.) affects maturity time but maturity is also influenced by environmental conditions such as temperature, planting date and location. The easiest and most economical method for determining maturity was phenological or visual observation. The best character to define physiological maturity (PM) was head first stage, when the brown color (1 to 10%) was visually observed at back of sunflower heads in visual observations. Determination of PM with phenological observation and seed moisture or seed maximum oil content together was the most accurate method for evaluation of physiological maturity. Hybrids decreased to about 300-400 g/kg moisture and reached maximum oil content at physiological maturity. Correlation results at physiological maturity showed that hybrids usually displayed similar days and heat unit accumulations at flowering and other early stages. Therefore, the earliest stage to accurately predict PM was 50 % blooming stage for most hybrids. Day accumulations were found to be less variable than heat unit accumulations in this study.