3363 Advances in Environmental Biology, 5(10): 3363-3368, 2011 ISSN 1995-0756 RTICLE A RIGINAL O This is a refereed journal and all articles are professionally screened and reviewed Corresponding Author Seyed Gholam Reza Moosavi, Assistant Professor of Islamic Azad University, Birjand Branch, Birjand, Iran. E-mail: s_reza1350@yahoo.com Effect of Irrigation Intervals and Planting Patterns on Yield and Qualitative Traits of Forage Sorghum 1 Seyed Gholam Reza Moosavi , 2 Mohamad Javad Seghatoleslami, 3 Hamed Javadi and 4 Elham Ansari-nia 1,2 Assistant Professor of Islamic Azad University, Birjand Branch, Birjand, Iran 3,4 Member of Young Researchers Club, Islamic Azad University, Birjand Branch, Birjand, Iran. Seyed Gholam Reza Moosavi , Mohamad Javad Seghatoleslami, Hamed Javadi and Elham Ansari-nia: Effect of Irrigation Intervals and Planting Patterns on Yield and Qualitative Traits of Forage Sorghum ABSTRACT In order to study the effect of irrigation intervals and planting pattern on the yield, yield components and qualitative traits of forage sorghum (Speedfeed variety) was conducted an experiment in Research Field of Islamic Azad University, Birjand, Iran in 2006. The experimental design was split plot in form RCBD with three replications and with 4 levels of irrigation interval (5, 10, 15 and 20 days) as main plots and 2 levels of planting pattern (one row above the furrow and two rows into the furrow) as sub plots. The irrigation intervals had a significant effect on the yield and yield components of forage sorghum but the planting pattern and the interaction of the irrigation intervals × planting pattern had no significant effect on these traits. The increase in irrigation interval from 5 to 20 days decreased the weight of the dry leaf, stem, ear and total fresh weight (sum of two cuttings) by 57.2, 72.1, 69 and 66.9 percent, respectively. The total dry forage in 5 days irrigation interval was 16.9 ton/ha which in comparison to 10, 15 and 20 days irrigation intervals advanced by 19.4, 44.3 and 66 percent, respectively. The irrigation intervals had a significant effect on the leaf to stem ratio and protein yield (sum of two cuttings). The comparison of mentioned traits averages in this experiment showed that with the increase of irrigation intervals, the leaf to stem ratio increased but protein yield decreased, significantly. The yield of crude protein with the increase of irrigation interval from 5 to 20 days decreased by 66.5 percent. The result of this research showed that water stress had negative effect on forage production and qualitative traits but planting pattern had not significant effect on these traits. Key word: forage sorghum, irrigation intervals, planting pattern, yield, qualitative traits. Introduction Drought is a worldwide problem, constraining global crop production seriously and recent global climate change has made this situation more serious [8,10,34,35,36,37,38,39,40,41,42,43,44,45,]. Under dry environmental conditions plants develop different mechanisms to resist and survive. These mechanisms are commonly based on morphological and physiological responsessuch as LAI reduction, that delay the water deficit [13]. Water deficit (commonly known as drought) can be defined as the absence of adequate moisture necessary for a plant to grow normally and complete its life cycle [32]. Water scarcity and drought are the main features of the dry areas. Water is the single most limiting resource for world agriculture and food production, highly exceeding other key limitations. Large amount of water is used in field production of food crops, leading to a deficit of fresh water resources in many arid or semi-arid areas in the world. In regions where water scarcity is the principal limiting factor for cultivation, farmers are interested in growing crops that are able to adapt to drought conditions [4,21]. Sorghum is becoming an increasingly important forage crop in many regions of the world [32]. Its high resistance to drought makes it a suitable crop for semi-arid areas [31]. Sorghum can responsed to additional irrigation by stem elongation and increase of yield [27,29]. [23] were reported that water deficit stress reduced quantitative and qualitative yield included total fresh weight, total dry weight, leaf dry weight, stem dry weight, protein yield and leaf/stem ratio of forage millet " nutrifeed " [14] were reported that significant difference between irrigation intervals of 8, 12, 16 and 20 days for fresh- feed yield and dry- feed yield were obtained in forage sorghum. In this study, highest fresh and dry-feed yield (52.4 and 15.5 ton/ha, respectively) obtained when 8 days irrigation interval was applied. [25] were reported adverse