Isabgol (Plantago ovata L.) is largely used in pharmaceutical industry, food preparations, ayurvedic medicine, remedies and preparation of crude drugs. In order to study the impact of different nitrogen amounts on quantitative and qualitative yield of isabgol, an experiment was conducted based on randomized completed block design with three replications, at Agricultural Research Station, College of Agriculture, Ferdowsi University of Mashhad, during growing season of 2011-2012. Treatments included four levels of nitrogen fertilizer (zero (N0), 25 (N25), 50 (N50) and 75 (N75) kg.ha-1). Plant height, biological yield, seed yield, and mucilage content of isabgol were measured. The results indicated that the effect of different amounts of nitrogen was significant (p≤0.05) on all studied traits of isabgol. By increasing in nitrogen application improved plant height, biological yield and seed yield and declined mucilage content of isabgol. The highest and the lowest seed yield were observed in N75 and control with 506.0 and 475.8 kg.ha-1, respectively.

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