Allelopathy of Ageratum conyzoides Ⅷ. Allelopathic Effects of Residues on Peanut and Related Weeds in the Field
胜红蓟化感作用研究 Ⅷ.植株对花生和相关杂草的田间化感效应

Ageratum conyzoides is one of exotic weeds in South China and Southeast Asia. The allelopathic potential of A. conyzoides is one of the reasons that it becomes a dominant and widespread weed in managed ecosystems. However, in some specific agroecosystems, both the allelopathic potential and fertility of A. conyzoides residue can be beneficial to crops. In order to investigate allelopathic effects of A. conyzoides residue on peanut and related weeds in the field, treatments both mixed the residues of A. conyzoides into soil and covered soil by the residues of A. conyzoides, and 4 periods of seeding, 10d, 20d, 30d and 40d after conducting the two treatments, were designed respectively. The study showed that the two treatments had significant different effects on peanut both in releasing allelochemicals and other physical factors under field conditions. The seedling emergence of peanut sowed immediately after done treatments were inhibited in mixed and promoted in covered residues of A. conyzoides. However, peanut's seedling emergence would be inhibited both in 10 days after mixed A. conyzoides residues into soil and 30 days after covered soil with A. conyzoides residues. It revealed that the residues of mixed treatment released allelochemicals more quickly and accumulated more amounts of allelochemicals in soil than that of covered treatment. Under conditions of seeding immediately after done treatments, the growth of peanut was not inhibited by covered treatment. However, peanut's growth was inhibited significantly by mixed treatment or seeding in 30 days after covered treatment. It demonstrated that the residues of mixed treatment released enough allelochemicals to inhibit the seedling emergence and growth of peanut. In two treatments of the field, it could be observed similar results that some kinds of weeds would be restrained to germinate and grow, and some would be promoted slightly or no influence. Further research results by HPLC revealed that difference of allelopathic inhibitory effect of A. conyzoides residue on peanut and related weeds in different treatments of field resulted from effective concentrations of agerotochromene released by the residues in different period. It also showed that the residues slowly released ageratochromene into soil after 14 days in covered treatment. The effective concentrations of ageratochromene in soil reached maximum value after 30 days and then reduced gradually in covered treatment. The residues of mixed treatment began to release ageratochromene in second day, and the concentration of ageratochromene in soil reached maximum value in 10 days and then reduced gradually. And, content of ageratochromnene in soil increased in 26 days, and then reduced gradually. The results demonstrated that the allelopathic inhibitory effects of A. conyzoides residue on peanut and related weeds significantly correlated with the different treatments and periods of the residues and effective concentration of ageratochromene