Study on the allelopathy effect and allelochemicals content of extracts from different ages of alfalfa on cotton

The allelopathy of alfalfa was studied by the method of bioassay of culture plate and filter paper in order to explore how the treatments with three extract concentrations (0.100,0.050,0.025 g/mL) of alfalfa affected the growth and germination of cotton. The results showed that the extract concentrations of alfalfa apparently inhibited the growth of seedling and root of cotton, and the inhibition was stronger with the increase of extract concentrations. Treating cotton seeds with extracts from leaves and stem of 2yearold, 3yearsold and 4yearsold alfalfa, the cottons seed germination were lower than the comparison, and the difference was significant (P＜0.05). The strongest inhibition occurred in extract from 3yearold alfalfa leaves and stem. Four phenolic acids content of the alfalfa aqueous extracts were analyzed with high performance liquid chromatography (HPLC). The four phenolic acids content was the highest in 3yearold alfalfa leaves and stem extract, followed by 4yearold alfalfa leaves and stem extract, 2yearold alfalfa leaves and stem extract, 2yearold alfalfa root, 4yearold alfalfa root, and 3yearold alfalfa root extract, sequentially.