Two experiments in two different seasons were conducted to study the effects of nitrogen form of nutrient solution on two greenhouse cucumber cultivars. Five nutrient solutions with different ratios of NH4/NH4+NO3, two cucumber cultivars (Soltan, Pardis), three replications and three plants in each plot were used in a split plot design. At the end of each experiment the characteristics of fruit yield, leaf and fruit dry matter percentage, and amount of nitrogen, phosphorus, potassium, calcium and magnesium in leaves were measured. Compound analysis of the two experiments revealed that: Fruit yield gradually decreased when NH4—N (in nutrient solution) increased. Maximum fruit yield was obtained in plants nourished withnon NH4—N containing solution (approximately 5.6 kg), and minimum from plants nourished with high NH4—N containing solution (4.2 kg). Leaf and fruit dry matter decreased for nutrient solutions with a high concentration of NH4—N. Total nitrogen and phosphorus in leaves increased, while potassium, calcium and magnesium decreased with increasing ammonium concentration in solutions, which indicates antagonistic effect of elements. Yield in Pardis cultivar was more than in Soltan with other characteristics being also different between the two cultivars. It was concluded that cucumber cultivars prefer NO3—N to NH4—N.
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