Relative importance for traits of some sunflower varieties under some agricultural practies

Two field experiments were carried out in 2002 and 2003 seasons at ElSheakh Zowid Research Station, Desert Research Center, North Sinai Governorate, to study the effect of three levels of irrigation levels, and three nitrogen fertilizer treatments (30, 45, 60 kg N/ fed.) on yield and yield components, of three varieties of sunflower namely Mayak, Pioneer-6480 and Hytic. The obtained results showed that the average values of number of days to flowering, plant height, stem diameter, head diameter, weight of 1000 seed, plant seed yield, seed yield/fed., seed oil percentage and oil yield/fed- were significantly affected by irrigation systems in both seasons. Also all studied characters were significantly increased by increasing nitrogen level up to 45kgN/fed. Mayak variety markedly exceeded both Pioneer - 6480 and Hytic varieties for all studied characters in both seasons. The interaction effects between different alternative irrigation systems and nitrogen fertilizer were significant for all studied characters in both seasons except for seed oil percentage in the second season. The interaction between irrigation and sunflower varieties had significant effect on number to days to flowering, stem diameter, head diameter and weight of 1000 seed in the first season, whereas, plant height, stem diameter, weight of 1000 seed, plant seed yield, seed yield/fed. and seed oil percentage were significantly affected in second season. Heaviest plant seed yield, seed yield/fed. and oil yield kg/fed. were obtained from planting Mayak cv, fertilized with 45 kg N/ fed. in both seasons. However, these characters gave the lowest values by planting Hytic cv, fertilized with 30 kg NI fed. in both seasons. The interaction of irrigation systems, nitrogen fertilizers and sunflower varieties had signif ant effect on stem diameter, head diameter and weight of 1000 seed in the two seasons. This interaction significantly affected number of days to flowering in i'ic first season and oil yield/fed. in the second season. High ~ st dficant and positive correlation coefficients were found among each of plant seed yield, seed yield/fed. and oil yield/fed. with all characters. Multiple linear regression analysis showed that number of days to flowering, plait height, stem diameter, head diameter, weight of 1000 seed, seed yield/fed. and seed oil percentage were ti;. most effective traits on oil yield/ fed. Stepwise regression analysis detected that number of days to flowering, head diameter, seen yield/fed. and seed oil percentage were the most contributing variables in the total variation of oil yield/fed. The results of path coefficient analysis indicate that, head diameter and weight of 1000 seed were the major and the most consistent sources accounting for 92.61% of plant seed yield variation while number of days to flowering, head diameter, seed yield/fed. and seed oil percentage were the major and the most consistent sources accounting for 97.93 of oil yield variation.