Two field experiments were conducted at the Extension
Field near Nit Ghmr. Dakahija Governorate to evaluate
effects of rates and application treatments of the ferti
lizer N on growth and productivity of sunflower in 1967 and
1968 seasons. Rates were 0, 20, 40 and 60 kg N/fad. Appli
cation treatments were six dose—time combinations. Results
obtained showed that N significantly affected at least six
growth characters out of nine. These were mid—flowering
date, plant height, number of groen leaves/plant, number of
dry leaves/plant, stem diameter and leaf area (LA). N had
unfavourable effects on percentages of lodged and broken
plants, which were both increased by N rates. No signifi
cant differences were detected among rates except for plant
height in favour of 60 kg/fad. and the number of dry
leaves/plant in favor of 20 kg N/fad, in one season only.
LA increased significantly with 60 kg N/fad in both seasons.
Results obtained suggest that the rate equals to 20 kg
N/fad. could be considered sufficient for supporting good
growth of sunflower in that niche. Dose—time combinations
were about equal In their effects. In addition, no signifi
cant interaction of rate dose—time combination was detected
indicating the independence of both factors in effect.