A Preliminary Study On The Allelopathy Of Vetiver And A. Fruticosa To Legume Crops

The previous studies suggested that the effects of Vetiver and A. fruticosa in soil and water conservation were significant. However, the impact of allelochemical yield from Vetiver and A. fruticosa on crops was not clear. Analysis of allelochemical and allelopathy is very important for the generalization of Vetiver and A. fruticosa in red soil region. In this study, the chemical compounds extracted from rhizosphere soil and aerial part of Vetiver and A. fruticosa were analysised by GC-MS method. After that, the allelopathy effects of aqueous extract on soybean and faba bean were revealed through the experiment of germination , seedling growth, and modifications. The main results were listed as follows:1. Main chemical compounds in the aqueous extract from rhizosphere soil of Vetiver were DL-Lactic acid, 2-Methyl-4-pentenoic acid, o-Hydroxypropiophenone, DL-Tartaric acid, Syringic acid. Main chemical compounds in the aqueous extract from aerial part of Vetiver were Formic acid, DL-Lactic acid,Phenol, 2-Methyl-4-pentenoic acid, 2-Methylbenzal dehyde, Benzoic acid, D-Limonene, Salicylic acid, Non-2-en-1-ol, DL-Tartaric acid, vanillic acid, Suberic acid, 7-methoxyxoumarine, p-Methoxycinnamic acid, Benzoic acid, 3,4-dihydroxycinnamic acid, Ferulic acid, Syringic acid, Palm acid. Main chemical compounds in the aqueous extract from rhizosphere soil of A. fruticosa were 2-Methyl-4-pentenoic acid, 3-Methylbenzal dehyde, 1—Naphthalcotanol, o-Hydroxypropiophenone, DL-Tartaric acid, p-Methoxycinnamic acid. Main chemical compounds in the aqueous extract from aerial part of A. fruticosa were Formic acid, Propionic acid, 2-Methylphenol, 2-Methyl-4-pentenoic acid, Succinic acid, 2-Methylbenzal dehyde,Benzoic acid, D-Limonene, Salicylic acid, 4-Hydroxybenzoic acid, Cinnamin acid, 3-Phenylpropionic acid, DL-Tartaric acid, 3,4-Dihydroxybenzoic acid, Vmbelliferone, 4-Coumaric acid, 7-methoxyxoumarine, Syringic acid, Palm acid.2. The germination of soybean and faba bean seeds was all inhibited by the aqueous extract from aerial part of Vetiver and A. fruticosa. Therefore, the inhabitation effect became stronger when the concentrations increase. The germination time of the faba bean seeds were delayed by the aqueous extract from rhizosphere soil and aerial part of A. fruticosa, thus influence the seedling growth.3. There was no significant inhibition on the seedling growth of soybean treated withthe aqueous extract from rhizosphere soil of Vetiver and A. fruticosa and from aerial part of Vetiver. The seedling growth of faba beans were promoted by the aqueous extract from rhizosphere soil of Vetiver and A. fruticosa, especially for the above-ground part. Extract from aerial part of A. fruticosa significantly inhibited the seedling growth of soybean, for both of the growth of above-ground and the root, and stronger with the increasing of concentration. And there was no significant inhibition on the seedling growth of faba beans treated with the aqueous extract from aerial part of Vetiver and A. fruticosa.4. Activated charcoal can absorb organic substances, and is often used to mitigate allelopathy. And it can also increase the microorganism activity which helps to reduce the allelochemical content. As the result shows, activated charcoal reduces the inhibition effect of the seedling growth of soybean which induced by the aqueous extract from aerial part of A. fruticosa. But the seedling growth of faba bean which treated by the aqueous extract from aerial part of Vetiver and A. fruticosa was inhibited after adding the activated charcoal. It may be caused by the allelochemical from the aqueous extract decomposed by microorganism.5. The nitrogen nutrient solution can promote the growth of plant. But there was no promotion in the growth of faba bean treated by the aqueous extract from aerial part of Vetiver and A. fruticosa. It may caused by the allelochemical compounds in the aqueous extract.6. With the residue time increased the allelochemical in the aqueous extract was decreased by the volatilization and decomposition process. With the increasing of the residue time, the seedling growth of soybean treated by the aqueous extract from rhizosphere soil of Vetiver and A. fruticosa was inhibited. And the inhibition to the seedling growth of soybean treated by the aqueous extract from aerial part of Vetiver and A. fruticosa was weakened with the residue time increasing.