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Abstract
Field experiment was carried out at the Experimental Station Farm in Giza, Agricultural Research Center, Egypt, during the two successive summer seasons of 2012 and 2013 to study the effect of varying sources and rates of nitrogen fertilizers on fresh and dry forage yield of sudangrass, chemical constituents, nitrate and nitrite accumulation in plant. The experiment was carried out in a split-plot design with three replications. The main plots were assigned to nitrogen fertilizers sources (Ammonium nitrate ”NH4 NO3” 33.5 % N and ammonium sulphate ”(NH4)2 SO4” 20.6 % N). While, the sup-plots were occupied with rates of nitrogen fertilizer (50, 75, 100 and 125 kg N/fed). The results indicated that fresh and dry forage yield, nitrogen, crude protein, phosphorus, potassium, nitrite and nitrate contents were significantly decreases in the second cutting as compared with the first cutting over both seasons. Using ammonium sulphate ”(NH4)2 SO4” as a source of nitrogen was better than using of ammonium nitrate ”NH4 NO3” as a source of nitrogen over both cuttings and seasons. Fresh and dry forage yields of sudangrass were significantly increased as nitrogen rates were increased from 50 to 75 and 100 kg N/fed, and significantly decreased due to increasing nitrogen rate from 100 to 125 kg N/fed over both seasons. By increasing nitrogen fertilizer rates, nitrogen, crude protein, phosphorus, potassium, nitrite and nitrate contents in s udangrass plants were significantly increased in the first and the second cuttings as combined over both seasons