Amelioration of Autotoxic Soil Constraints to Lettuce and Mat-rush Growths by Activated Charcoals

Abstract

Phytotoxic effects of root exudates of mat-rush (Lomandra longifolia Labill.), which accumulated in the soil by the continuous mat-rush cultivation were evaluated for the growth of lettuce (Lactuca sativa L.) and mat-rush seedlings. A soil with continuous mat-rush cultivation for over three years was used for this study. A 210 ml of soil was amended with the different fineness of 1.53 g activated charcoals (AC): coarse-AC and fine-AC. The soils without the AC amendment (non-AC) and without previous mat-rush cultivations (control) were also prepared. The stem length, root length, and fresh shoot and root weight of lettuce grown in the non-AC soil were reduced to 67, 24 and 55% of those found in the control, respectively. The soil amended with the coarse and fine AC improved these growth parameters. The growth reduction of plants grown in the non-AC soil may likely appear to be related to allelochemicals exuded from the mat-rush root because there were negligible changes in soil physical and chemical properties between the non-AC and AC amended soils. The detrimental effects of soils used for a continuous mat-rush cultivation on following plant growth can be ameliorated by the addition of AC to the soil.