Effect of N fertilization and plant density on yield and yield components of grain sorghum under climatic conditions of Sistan, Iran

In order to study the effect of different levels of N fertilization and plant density on yield and yield components of grain sorghum cv. Sistan, an experiment was conducted in agricultural research farm of Zehak, Iran in 2009 as a split-plot experiment based on a Randomized Complete Block Design with three replications in which the main plot was dedicated to N fertilization (at four levels of 0, 75, 150 and 225 kg N ha-1) and the sub-plot to plant density (at four levels of 12, 15, 25 and 50 plants m-2). It was found that N fertilization levels significantly influenced all studied traits except panicle number per m2 and the changes in plant density affected all studied traits significantly. In addition, the interaction between N fertilization and plant density was significant for gain number per panicle, 1000-grain weight, grain yield, biological yield and harvest index. Means comparison of simple effects revealed that the application of N fertilizer up to 150 kg ha-1 increased grain number per panicle, harvest index and grain yield significantly. Furthermore, although the increase in plant density up to 50 plants m-2 resulted in the significant loss of 1000-grain weight, grain number per panicle and harvest index, it significantly improved grain yield owing to the significant increase in panicle number per m2. In total, it was found that if N fertilization sufficed, the increase in plant density would effectively improve economical yield of sorghum so that the highest grain yield of 2388.33 kg ha-1 was obtained from the treatment of 225 kg N ha-1 at the density of 50 plants m-2. Therefore, it is recommended to apply 225 kg N ha-1 and to use the density of 50 plants m-2 to realize optimum yield of grain sorghum cv. Sistan in Zabol region, Iran.