The objective of this study was to investigate the effects of different nitrogen fertilizers
(potassium nitrate and / or urea) on root growth, leaf area ratio, pigments content and
carbohydrate content of leguminous plant Vigna sinensis and non-leguminous plant Helianthus
annuus, throughout two vegetative stages. Root criteria,in general non-significantly affected by
the used source of nitrogen during the two vegetative stages of cowpea and sunflower plans
growth. Concerning the leaf area ratio, except for the observed non-significant increase in
response to treatment with 100% potassium nitrate + 100% urea at second stage, the other
treatments was non-significantly decreased this ratio during the two vegetative stages of the two
plants. Total chlorophyll and total pigments were increased by the used treatments at first stage of
cowpea growth while these parameters were decreased during the second stage and vice versa in
case of sunflower plant. Sucrose content of the two plants, was significantly increased by all used
treatments at first vegetative stage. On the other hand, the different treatments led to a general
increase in the determined carbohydrates (total soluble sugars- sucrose- polysaccharides – total
carbohydrates) as compared to control values during second stage of the two plants. The result of
this investigation demonstrated that, nitrogen fertilizers has an overall positive influence on
growth, photosynthetic pigments and sugars especially in case of using (50% potassium nitrate +
50% urea) and the magnitude of response was more pronounced in case of cowpea plant.