Effect of Sowing Date and Preceding Crop, on Growth and Productivity of the Sunflower Hybrid Sirena, Under Varying Nitrogen Fertilization Levels

SUNFLOWER is an important oil crop that has received great attention by the Egyptian agricultural sector in the early nineties, when a boom in oil extraction from the crop was observed. Since then and for more than two decades now, sunflower for oil purpose was neglected, hybrids are no longer on the market and confectionery sunflower became more profitable for Egyptian farmers. Recently, the registration of the single hybrid Sirena and its promotion based on contract basis with farmers, may present a new comeback to oil sunflower in Egypt. The aim of this study was to evaluate effect of sowing date (April vs. August) and preceding crop (maize vs. sunflower) in a double cropping system, under varying nitrogen fertilization levels (36, 72, 108 and 144kg N/ha), on growth and productivity of the newly introduced sunflower hybrid Sirena. Results from the two-year experiments, indicated that April sowing, at a prevailing average temperature of 20-24oC later rising to about 28oC at harvest time, was suitable to secure maximum seed yield of 4.39ton/ha. In a double cropping system, where sowing was performed in August, the hybrid yielded an average of 3.4 ton/ha, whether preceded by maize or sunflower. Seed oil percentage amounted to an average of 42.8% and was affected by the year, rather than sowing date or preceding crop. Effects of the nitrogen fertilization rates were masked by the soil available nitrogen, however, based on the regression analysis and equations for estimating the nitrogen requirements based on the hybrid seed yield, 72-108kg N/ha were necessary to achieve the maximum seed yield while sustaining an oil percentage above the 42%.