Rajan Katoch, Anita Singh, Neelam Thakur/ International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue 5, September- October 2012, pp.828-834 828 | P a g e Effect Of Weed Residues On The Physiology Of Common Cereal Crops Rajan Katoch, Anita Singh and Neelam Thakur a Department of Crop Improvement, College of Agriculture, CSK Himachal Pradesh Krishi Vishvavidyalaya, Palampur (H.P.) – 176 062 (India) a Department of Biosciences, Punjab Agricultural University, Ludhiana, India, 141004 * Corresponding author: Dr. Rajan Katoch Department of Crop Improvement, College of Agriculture CSKHPKVV, Palampur (H.P.) – 176062, India Abstract The allelopathic influence of plant residues of three dominant weeds of North- Western Himalayan region, namely, Eupatorium adenophorum, Ageratum conyzoides and Lantana camara was observed on the germination and early growth of three common cereal crops viz., Triticum aestivum cv. HPW-42, Oryza sativa cv. Hasanshrai Basmati and Zea mays cv. Girija. The effect of soil amended with weed residues at two concentrations (5 g/100 g soil and 10 g/100 g soil) was compared with control. Among the test crops, maize with larger seeds was least sensitive to the exposure to various treatments while wheat and paddy with small seeds were comparatively susceptible. The incorporation of weed residue in soil had inhibitory effect on the per cent germination and shoot length of seedlings of test crops. The results of the study indicated the allelopathic influence of weed residue on the physiology of the crop plants. Therefore, the intensive studies on allelochemicals released from decaying weed residues in the natural environment where additive or synergistic effects become significant even at low concentrations are desirable to provide detail information on the influence of the weeds on crops of economic interest. Abbreviations: Key words: weeds, weed residue, germination, shoot length, Triticum aestivum, Oryza sativa, Zea mays Introduction Weed infestation is one of the major causes of yield reduction in crops. The incidence of allelopathic effect of weeds on growth of crops has become increasingly widespread. When the two plant species grow together, they interact with each other either inhibiting or stimulating their growth or yield through direct or indirect allelopathic interaction (Kumar et al. 2006). Several reports have documented the deleterious effect of decaying weed residues on the growth and yield of subsequent crops in the field (Guenzi and McCalla 1966, Shaukat et al. 1985, 2003, Burhan and Shaukat 1999, Singh et al. 1988, Angiras et al. 1987, 1988, Das and Choudhury 1996). The effects of decaying weed residues depend upon the release of allelochemicals from them into the soil. These chemicals may be washed directly from the residues, or may result from microbial activity during decomposition (Putnum and Duke 1978, Lynch and Cannell 1980, Kumar et al. 2006). The effect of allelopathic chemicals tends to be highly species-specific (Stowe 1979, Melkania 1983). Normally, the effect is harmful, but beneficial effect is also possible (Newman 1978). Ageratum conyzoides, Lantana camara and Eupatorium adenophorum are three exotic rapidly spreading weed species which have successfully invaded a large portion of North-Western Himalayan region in India. They are a major problem for the environmentalists, ecologists and agriculturists. The present investigation was carried out to assess the allelopathic potential of the plant residues of these common weeds of North-Western Himalayan region on the important cereal crops viz., Triticum aestivum cv. HPW-42, Oryza sativa cv. Hasanshrai Basmati and Zea mays cv. Girija. Materials and Methods Collection and mechanical processing of plant material Fresh plant material (whole plant) of E. adenophorum, A. conyzoides and L. camara was collected from the vicinity of CSKHPKV, Palampur, India. The collected plant samples were allowed to shade dry. The dried material was crushed into fine powder using grinder and sieved through mesh of 2mm pore size. Procurement of seeds Seeds of the cereal crops studied were procured from the Department of Crop Improvement, CSKHPKV, Palampur. The seeds were surface- sterilized with sodium hypochlorite and used for further bioassay studies. Pot experiment To study the effect of decaying weed residue on germination and seedling growth of test crops, dried powdered material of E. adenophorum, A. conyzoides and L. camara was mixed thoroughly