International Journal of Agronomy and Plant Production. Vol., 4 (6), 1148-1157, 2013 Available online at http:// www.ijappjournal.com ISSN 2051-1914 ©2013 VictorQuest Publications The Inhibitory or Stimulatory Effects of chickpea Cultivars Extracts on Germination and Growth of Sunflower and Maize Elham Saeedi Pooya 1 , Somayeh Tokasi 2 , Mohammad Taghi Alebrahim 3 , Ebrahim Kazerooni Monfared 4 1- Msc., Student of Horticultural Sciences, Faculty of Agriculture, Ferdowsi University of Mashhad, Mashhad, Iran. 2- Ph.D Student of Weed Science, Dept. of Agronomy, Faculty of Agriculture, Ferdowsi University of Mashhad, Mashhad, Iran. 3- Assistant Professor of Weed Science, Department of Agronomy and Plant Breeding, Faculty of Agriculture, Mohaghegh Ardabili University-Ardabil, Iran. 4- Assistant Professor of Weed Science, University of Applied Science and Technology, Rasht, Iran. *Corresponding author: Ebrahim Kazerooni Monfared Abstract Cultivating a system with crop rotation can be reduced soil sickness by releasing chemical materials from crops but the residues of preceding crops affect the performance of other crops through the releasing of allelochemicals. Thus, in this study, we investigated the allelopathic effects of straw aqueous extract of four chickpea cultivars on germination and seedling growth of maize and sunflower. Two experiments were conducted as the factorial experiments based on completely randomized design with 3 replications including four chickpea cultivar extracts (Karaj‚ Jam‚ Flip and ILc480) at five concentrations (0, 5‚ 10‚ 20 and 40 %). Results indicated that, the degree of inhibition was depended largely on the tested extract concentrations. In addition to germination, seedling length and weight of two crop plants were reduced with increasing extract concentrations. Application of 40 % concentration decreased seedling weight 52.97% in sunflower and up to 80% in maize compared to the control. The lowest and the highest inhibitory effect were observed in Jam and Ilc480 extracts, respectively. Results could be useful for planning a high benefit rotation system based on crop suppressive effects. Keywords: Germination, Inhibitory, Residues, Rotation, Straw. Introduction Allelopathy is one of the most advanced mechanisms of plant defenses. It could be understood as a process whereby plants provide themselves with a competitive advantage by releasing phytotoxins into the adjacent environment by releasing chemicals, named allelochemicals (Bertin et al.‚ 2003; Scognamiglio et al.‚ 2012). Allelopathic crops play a considerable role in the establishment of sustainable agriculture. Allelopathic crops when used as cover crop, green manures, or grown in rotational sequences are helpful in reducing noxious weeds and plant pathogen, improve soil quality and crop yield (Khanh et al.‚ 2005). Cultivating a system with crop rotation can be reduced soil sickness by releasing chemical materials from crops (De Candolle, 1832). Where crop residues are left on the soil surface to avoid soil erosion, preserve moisture, increase nutrient balance and a number of other benefits. The residues of preceding crops affect the performance of other crops through the release of allelochemicals (Singh et al.‚ 2008). Residues from allelopathic crops can hinder germination and growth of following crops as well as weeds. Numerous crops showed inhibitory effects to other crops when cultivated either subsequently or simultaneously. Kalburtji and Gagianas (1997) reported the poor performance of cotton following the sugar beet crop due to allelochemicals released from the residues of sugar beet. Tesio et al. (2012) investigated the allelopathic effect of Helianthus tuberosus residues on the germination and early growth of crop and weed species. Seyed Sharifi et al. (2007) estimated that application of wheat, barley, safflower and sunflower