Study On Allelopathic Effect Of Alfalfa

Alfalfa (Medicago sativa L.) is one of the most excellent leguminous grasses in the world. It has characteristics with high yield and high quality, and strong adaptive capacity. It has also an important effect on grass arable system and improving soil fertility because of their nitrogen-fixing properites. With adjusting agricultural structure, the plant areas of alfalfa have been increased rapidly during the recent years. There were manifold planting patterns of companion cropping and crop rotation such as alfalfa with cereal crops or with commercial crop. However, it was found that alfalfa had strong allelopthic effects on other crops and autotoxicity in practice. It was very important to study allelopthic trait of alfalfa on establishing ternary agriculture-economy-forage structure, and develop some alfalfa cultivars with strong allelopthic effects, which can restrict weeds growth. They could be used to empolder biological herbicide, bactericide and insecticide.The ten cultivars of alfalfa introduced from abroad were used in the experiments. The allelopthic effect of alfalfa on germination, root and seedling of radish was studied with bioassay methods. The ten cultivars of alfalfa are Derby, Defi, Sitel, Sanditi, Northstar, Eureka, Alize, Alfaqeen, Alegro and Jindery. The phenolic acid contents of the aqueous extracts of aerial part and root of alfalfa were determined during the different stage of growth such as the seedling stage, the branching stage, the blooming stage, the fruiting stage and the regrowth stage by high performance liquid chromatography (HPLC), respectively. The content and mechanism between cultivars, growing stages and organs were compared. In addition, the effect of phenolic acids was studied on germination and seedling growth of radish and Italian ryegrass.The results showed that the aqueous extracts of aerial part inhibited germination, root and seedling growth of radish and Italian ryegrass. The inhibition varied with cultivars; Alegro, Alize, Sanditi and Defi were stronger than other cultivars and Alegro and Alize had a significant (p<0.05) autotoxicity.The allelopthy of alfalfa also varied with growing stages. The blooming stage and the fruiting stage showed significantly stronger allelopthy than the seedling stage, the branching stage and the regrowth stage of winter season.Comparing the allelopthic effect of the aqueous extracts of aerial part with that of the...