effect of biological and chemical nitrogen fertilizers and plant density on quan-titative and qualitative yield of silage corn

in order to study the effect of chemical and biological fertilizers on silage corn under different plant densities, a split plot experiment was carried out in a randomized completely block design with three replicates in south western iran. the main plot included nitrogen fertilizer treatment at three levels (n1: with out chemical and organic fertilizers, n2: 75% chemical fertilizer + 100% organic fertilizer, n3: 100% chemical fertilizer+ 100% organic fertilizer) and the sub plot was density in three levels (d1: 70000 plant.ha-1, d2: 90000 plant.ha-1, d3: 110000 plant.ha-1). the results showed that the highest fresh and dry weight of forage, stem, and leaf of the corn was related to the treatment with 75% urea and 100% nitroxin. d1 (70000 plant.ha-1) and d2 (90000 plant.ha-1) had higher yields than the other densities in terms of stem, leaf and forage dry weights, but it was not possible to identify appropriate density in terms of fresh weight of stem, leaf, corn and forage because the effects of different densities on these traits were not significant. n2 treatment had the highest rate of plant height, number of leaves per plant, and corn/plant ratio. n1 treatment without chemical or organic fertilizer had the lowest rate of mentioned features. moreover, n3 treatment had highest rate of protein and phosphor. interaction effect of fertilizer and density was not significant on all studied traits. generally, combined fertilizer treatment with 75% urea and 100% nitroxin had a significant effect on the increase of forage yield in comparison to control treatment (without chemical and organic fertilizer). the optimum plant density (90000 plant.ha-1) increased yield and more importantly due to competition and shadowing reduced the dry matter and yield in this experiment.