Allelopathic Activity of the Residues of Herbaceous Weed Species Common in Orchards

Cleome viscose L, Andrographis paniculata (Burm. f.) Nees, Ocimum sanctum L. and Celosia argentea L are common herbaceous weed species in orchards with allelopathic activity. This study was conducted to examine the allelopathic effect of residues on seed germination (SG) and growth of indicator plant radish, selected field crops (Eleusine coracana, Vigna radiata, Vigna mungo, Oryza sativa and Vigna unguiculata), and potential autotoxicity. The residue mixtures (1%, 2.5%, 5%, 10% and 15%) were prepared by mixing air-dried ground residues of weeds and sand. The seeds of radish, field crops and the same weed species were planted in different residue mixtures. Complete randomized design with 3 replicates was used for all experiments. The quantitative analysis for allelochemicals was also performed. Except for 1% of A. paniculata, other treatments significantly (p≤0.05) inhibited SG of radish and C. argentea showed the highest. A varied allelopathic effect on other field crops was observed but 5% and 10% of C. argentea residues exhibited 100% inhibition of SG of all field crops excluding paddy. All weed species also showed significant autotoxicity. The presence of the different amounts of total phenolic and flavonoid contents further verified the allelopathic effect of these weed species. These results indicated frequent adding of the residue of the weed species tested in this study would be able to inhibit seed germination and seedling growth of crops tested in this study and the prevalence of the same weed species in the field.