Allelopathic Effect of Nutsedge Weeds (Cyperus esculentus L.) and Redroot Pigweed (Amaranthus retroflexus L.) Plants Extracts on Germination and Seedling Growth of Rapeseed (Brassica napus)

Given the abundance of nutsedge weeds (Cyperus esculentus L.) and redroot pigweed (Amaranthus retroflexus L. ) in fields and also the importance of rapeseed (Brassica napus L.) as oil plant, this study was performed to evaluate the allelopathic effects of extracts from the aerial and underground organs of two kind of weeds including Cyperus (Cyperus esculentus L.) and redroot pigweed (Amaranthus retroflexus L.) with three levels of weed extract (5, 10 and 20 percent) with control on rapeseed germination and growth with a factorial experiment based on completely randomized design with four replications in 2010-2011at Vali-e-Asr University of Rafsanjan. The results showed that the extract of redroot pigweed significantly more reduced the above properties compared with nutsedge. The extract of organ type had a significant effect on the measured properties, as the extract of aerial organ significantly reduced germination rate, vigor index, root and shoot length of rapeseed, but it had no significant effect on germination percent. With increasing concentration of extract, germination rate, germination percent, vigor index, root and shoot length significantly reduced. Redroot pigweed organ extract had more inhibitory effect on vigor index and shoot length of nutsedge than the rapeseed organ extract. With increasing the concentration of extract, aerial organ of both weed species, germination rate and root length significantly decreased. Furthermore, the results showed that increasing concentration of redroot pigweed extract had more inhibitory effect on vigor index and shoot length of rapeseed than nutsedge. According to these results it can be deduced that redroot pigweed extract, aerial organ and increasing concentration of extract had maximum inhibitory effect on growth of rapeseed.