Mohmmad Hossein Aminifard - Department of Horticultural Science, Special Plants Regional Research, Faculty of Agriculture, University of Birjand, Iran
Hassan Bayat - Department of Horticultural Science, Faculty of Agriculture, University of Birjand, Iran

Purpose: Vegetables are important sources of carbohydrates, proteins, vitamins and minerals. Bell peppers, the fruit of Capsicum annuum L. is one of the most important commercial crops in the world. This study was conducted to determine the effects of nitrogen (N) doses on growth and yield of sweet pepper under field conditions. Research Method: Treatments consisted of 0, 50, 100 and 150 kg N ha−1. Plant height, Leaf chlorophyll index, flower number, yield, fruit seed number, 1000 seed weight and vitamin C were assessed at immature and mature. Findings: Nitrogen rate increasing affected significantly plant vegetative growth (plant height, lateral stem number, and leaf chlorophyll). The highest length and number of lateral stem and leaf number were obtained in plants treated with100 kg N ha-1.The results indicated that reproductive factors (weight and volume of fruit, plant yield, and 1000 seed weight) were influenced by nitrogen fertilizer. It was observed that fertilization with 150 kg N ha-1 resulted to the highest fruit weight and fruit yield. Although there were no significant differences in vitamin C content among treated plants with different nitrogen levels at a mature stage, it was shown significant differences between treated plants and control. Research limitations: If we could use several sources of nitrogen fertilizer such as ammonium nitrate and ammonium sulphate, then it was compared themو it seemed that we got better results about sweet pepper. Originality/value: Results showed that nitrogen fertilization has a strong impact on the vegetative, flowering and reproductive growth of pepper plants.

fruit quality, fruit yield, nitrogen, pepper