Effect of different levels of nitrogen fertilizer and plant density on quantitative and qualitative yield of silage maize (cv. SC 704) in Varamin

An experiment was conducted to evaluate the effect of different levels of nitrogen and plant density on quantitative and qualitative characteristics of silage maize (cv. SC704) in Varamin experimental field station in three consecutive growing seasons (2000-2002). The experiment was arranged in split plot, using randomizd compble block design (RCBD) with three replications. Four levels of nitrogen induding; No nitrogen fertilizer (N0), nitrogen fertilizer equal to the recommended rate based on soil test (N180), nitrogen fertilizer 30% more than recommended rate and nitrogen fertilizer 30% less than recommended rate (N230 and N130, respectively) assigned to main plots and plant density at four levels; 70 thousand plant/ha (D70), 90 thousand plants/ha (D90), 110 thousand plants/ha (D110) and 130 thousand plants/ha (D130) randomized in sub-plots. Combined analysis of variance showed that different nitrogen levels did not significantly affect total dry matter yield, stem, leaf, cobb, protein yield, diameter and plant height. Plant density significantly affected ear and leaf dry matter yield at 5% probability level, and interaction of nitrogen and plant density was significant on ear dry matter yield at 1% probability level. The highest dry matter 10.2 T/ha was produced in D130, treatment. Total dry matter 11.4, 11.3 and 10.2 T/ha, leaf dry matter yield of 2.2, 1.2 and 1.3 T/ha, cobb dry matter yield 3.3, 3.4 and 3.4 T/ha and protein yield 0.9, 0.8 and 0.7 Kg/ha were recorded in N230D110, N230D130, N180D130, respectively. Hence, it can be concluded that by increasing plant density to more than 50% of recommended and using of nitrogen fertilizer equal to the recommended rates based on soil test, can increase yield of silage maize and its quality.