Research on differences of component and quantity of organic acids in the root exudates among the three green manures

A hydroponic experiment was conducted to compare the differences in composition and amount of organic acids released from roots among three green manure species, including Lolium perenne, Vicia villosa and Astragalus sinicus. Oxalic, citric, malic, succinic and acetic acids were found in root exudates of Lolium perenne; Oxalic, citric, tartaric, malic, succinic, lactic and acetic acids were found in root exudates of Vicia villosa; Oxalic, citric, malic, lactic and acetic acids were found in root exudates of astragalus sinicus. The results further showed, 30 days after transplanting, the oxalic acid was the dominant organic acid in Lolium perenne while the citric acid and oxalic acid were main ones in Vicia villosa and astragalus sinicus; 50 days after transplanting, oxalic acid and citric acid were dominant organic acids in the three green manures. In addition, the components of each of root exuded organic acids among three kinds of green manures all increased with the growth stage to advance. However, the increasing rates were significantly different.The oxalic acid and malic acid exuded by Lolium perenne respectively increased by 2.5 and 10.0 times, and malic acid exuded by Vicia villosa increased by 1.9 times, and oxalic acid and acetic acid exuded by Astragalus sinicus respectively increased by 3.3and 8.0 times.