Studies On Allelopathic Effects Of Alfalfa On Several Weeds

Alfalfa named "the king of grass". It has multiple ecological functions because of its wide range of ecological adaptation.It has huge potential in ecological value and it was hailed eco-grass. Recently scholars are paying more attention to taking advantage of allelopathic characteristics of plants to control weeds. Some researches showed that alfalfa had certain allelopathic potential. It has practical significance to use the allelopathic capability of alfalfa to control weeds and reduce the application of herbicides.The allelopathy of fifteen cultivars of alfalfa was studied in culture plate and sand culture bioassays.. The cultivars of alfalfa are Alfaqeen,Phabulous, Sitel, Longdong, Sanditi, Derby, Ladak, Grandeur, Zhongmu No.1, Algonguin,WL-414,WL525HQ,WL-323HQ, WL-323ML and WL-323The acceptors were speedwell, bristlegass,redroot pigweed and barnyardgrass. The allelopathy of the aqueous extracts of stems and leaves from fefteen cultivars of alfalfa on gemination and seedling growth of the acceptors were investigated in order to study the difference among cultivars and concentration of the aqueous extracts. Nine phenolic acids in the aqueous extracts of stems and leaves from different cultivars of alfalfa were analyzed by high performance liquid chromatography (HPLC), which are Protocatechuic acid, ρ-Hydroxybenzoic acid, Salicylic acid, Caffeic acid, ρ-Coumaric acid, Ferulic acid, Syringic acid, Vanillic acid and Cinnamonic acid.The results showed that the allelopathy of alfalfa was significantly defferent among cultivars. The inhibition effects of Phabulous, Longdong and Zhongmu No.1were stronger than that of other cultivars, and followed by the WL-414, WL-323. The seed germination and seedling growth of speedwell, bristlegass, redroot pigweed and barnyardgrass were obviously inhibited by aqueous extracts of alfalfa. The inhibition effects of the aqueous extracts of alfalfa enhanced with the concentration of the aqueous extracts increasing.The sensitivity of the weeds to the aqueous extracts of alfalfa differed among species and organs of weeds. Speedwell and barnyardgrass were more sensitive to allelopathic suppression of alfalfa than bristlegass and redroot pigweed, and The sensitivity of seedling root is stronger than that of seedling. The results showed that the concentration of each phenolic acid or the total concentration of the nine phenolic acids were significantly different in the aqueous extracts of different alfalfa cultivars by high performance liquid chromatography (HPLC).The contents of protocatechuic acid, salicylic acid and cinnamonic acid were more higher than that of other phenolic acids in the aqueous extracts of fifteen alfalfa cultivars respectively. And content of the three phenolic acids occupies a much high proportion of total phenolic acid in the aqueous extracts of Phabulous, Longdong, Zhongmu No.1and WL-323which were with higher allelopathic inhibitory potential on weeds. Salicylic acid occupies a much high proportion of total phenolic acid in the aqueous extracts of Phabulous, Longdong and WL-323, which was more than64%. Protocatechuic acid occupies a much high proportion of total phenolic acid in the aqueous extracts of the aqueous extracts of Derby, Algonguin and WL-323which was more than58%.The contents of Protocatechuic acid and salicylic acid of the aqueous extracts of stems and leaves from fefteen cultivars of alfalfa were were higher than other phenolic acidsduring the flowering season of alfalfa, and.The contents of two phenolic acids were29.29μg/g～128.33μg/g and62.03μg/g～167.02μg/g relatively.Therefore, in practice when we select appropriate cultivars of alfalfa, we not only consider the yield and quality of cultivars but also consider the allelopathic inhibitory effect of them.so that we are able to reduce the dosage of herbicide and to carry out the sustainable development of agriculture.