The oil content of sunflower hybrids is influenced by the complex effect of several factors. Crop year has a significant role mainly in terms of the weather circumstances at the time of sowing, flowering, fertilisation and oil incorporation (precipitation, weather, humidity). Agrotechnical factors have a significant impact on oil content. The examined sowing technological factors have a major role and they contribute to the increase or decrease of oil incorporation indirectly or directly.

Based on the experimental results, it was observed that fungicide control can also significantly alter the oil content of sunflower. Yield has a major impact on oil yield, while oil content is less determinant.

Averaged over the various treatments, the change of sunflower oil content was examined against sowing technological elements in the case of three plant protection models. Oil content increase was observed in all three crop years during the plant protection performed at the eight leaf pair stage. This increase was the highest in the wet crop years.

During the second phase of plant protection at the flowering stage, a significant reduction of oil content was observed. The extent of this reduction was high even in the drought year (2009: 0.9%), but it was higher than 1% in the strongly wet year of 2010. In all three years, oil yields were the highest in the population which was treated twice, but the increase of oil yield was more intense as a result of the first treatment – the efficiency of the second treatment was also higher in the wet crop year. Increasing the population density resulted in the parabolically decreasing growth of oil content in 2008 and 2009. In contrast, oil content stagnated in 2010 and there was no major change. Oil content had a similar trend as yield. In the drier crop year, higher oil yield was obtained by means of higher population density (55 000–65 000 plants per hectare), while the optimal population density was lower (45 000–55 000 plants per hectare) in the more rainy year of 2008. In addition to population density, the volume of oil incorporation was also affected by sowing date. In 2008 and 2009, the oil content of plants sown in mid-April (average) was lower than in the case of early and late sowing date which is probably the result of the weather anomalies occurring during the sowing and flowering stage of the sunflower population with average sowing date. In 2010, average sowing date was proved to be the best, since the average oil content was 0.4% higher than in the case of early sowing date and 0.5% higher than populations with late sowing date. In wet crop years, the oil contents of early sowing date were higher, while the highest yield and oil yield of the dry crop year of 2009 were obtained in the case of average sowing date.

Keywords: sunflower, oil content, population density, sowing date, fungicide control