The intensity level of the production of the main Hungarian field crops is different. As opposed to maize which is produced under average or intensive circumstances, the expenditure level of sunflower production is only extensive or average. Nowadays, average sunflower yield is between 2-2.5 t ha-1 in Hungary. In the recent decades, the signs of climate change were becoming increasingly prominent (unevenly distributed precipitation over the growing season, drought periods, low temperature, etc.) which increased the amount of yield fluctuation to more than 50% in the recent period. The aim of this research is to explore the agrotechnical needs of the examined sunflower hybrids under different weather circumstances. The experiment was carried out in the Látókép Crop Production Experiment Site of the University of Debrecen, Centre for Agricultural and Applied Economic Sciences on calcareous chernozem soil in drought (2009), wet (2008) and strongly wet (2010) crop years. The hybrids were sown at early, average, and late sowing dates and four theoretical crop density values were used (35 000 – 65 000 plants per hectare) with steps of 10 000 plants per hectare. As regards fungicide treatment, there were non-treated crop stands, as well as stands treated once and twice in the experiment. The different weather circumstances of the three examined years strongly affected the efficiency of the fungicide treatments, thereby influencing the sowing technological models. The proportion of stem lodging and stem breaking under the head decreased in the case of later sowing dates, lower crop density and with the increase of fungicide treatments and it increased in opposite cases. However, there were significant differences in the proportions of lodged sunflowers and those with broken head within a plot during the three growing seasons. The impact of fungicide treatment could be observed in each growing season and crop density. This impact was expressed in the decreasing level of infection, lodging and stem breaking under the head. In the strongly wet growing season, there was a significant decrease of lodging and stem breaking under the head as a result of fungicide treatments in comparison with the control (higher than 14%). The fungicide treatment played an important role in reducing the impact of improperly selected sowing technological elements. The difference between the level of infection, as well as that of stem lodging and head breaking was lower at the optimal and most disadvantageous sowing dates and crop densities in the case of different fungicide treatments (1x and 2x) in all cases in the experiment years in comparison with the control plots. Based on the examination results, it was concluded that modern sunflower hybrids need at least average or intensive technological intensity. In order to maintain the proper crop health status, at least two fungicide treatments should be performed in wet crop years (at the 8-10 leaf pair stage and at flowering), but even average or drought growing seasons call for the application of one fungicide treatment at the 8-10 leaf pair stage. The optimal sowing date in mid-April and moderate crop density (55 000 plants per hectare) could be the effective tool of maintaining yield stability independently of crop years.

Keywords: sunflower, crop density, sowing date, stem rigidity, disease infection, fungicide crop protection