Abstract
In order to study the effect of amounts and methods of nitrogen application on quantitative and qualitative characteristics of forage sorghum (Sorghum bicolor (L.) moench var. speed feed) an experiment was conducted as split plot based on compeletely randomized block design with 3 replications. In this study 3 amounts nitrogen fertilizer including (80.5, 161 and 241.5 kg/ha) were used as main plots and 3 methods of nitrogen application including in one stage (total fertilizer applied after planting), two stage (one-half fertilizer applied after planting and one-half after first harvest) and three stage (one-third fertilizer applied after planting, one-third after first harvest and one-third after 6 to 8 leaves regrowth) as sub plot. Results showed that the effect of amounts and methods of nitrogen application in first, second and sum of two harvests on dry matter forage yield and protein yield was significant. Methods of nitrogen application in two and three stage were better than one stage, and nitrogen amounts of 80.5 and 161 kg/ha were better than 241.5 kg/ha, which provide better condition for crop development and growth, because the crop used better of environmental factors than the other treatments. The effect of amounts and methods of nitrogen application were not significant on plant height and number of tiller. Effect of amounts and distribution method of nitrogen fertilizer was significant on percentage fiber and ash at first harvest and protein percentage of second harvest. The highest protein percentage and ash and the lowest fiber percentage were obtained from 80.5 (N) kg/ha and application in three stages. Interaction between amounts and methods of nitrogen was not significant on studied traits, other than on protein percentage at first application and ash percentage at second harvest. The results showed that the maximum yield quantitative and qualitative were obtained by using of nitrogen fertilizer amount of 80.5 kg/ha by two or three stage application.

Keywords: Forage sorghum, Amounts and Methods of nitrogen application, Quantitative and qualitative yield