Allelopathic Effects of Black Radish (Raphanus sativus L. var. niger J. Kern.) and Garden Cress (Lepidium sativum L.) Plants on Johnsongrass (Sorghum halepense (L.) Pers.) Plant in Tomato Cultivation

Abstract

This study aimed to investigate the effectiveness of black radish and garden cress as pre-plant in field trials and their aqueous extracts under greenhouse conditions to control johnsongrass. In the field experiment, black radish and garden cress were grown as a pre-plant, then mixed with the soil and used with and without mulch against johnsongrass. The effects of these applications on johnsongrass development and tomato yield and quality were evaluated. Different concentrations of pre-plant extracts (2, 5, and 10%) were also investigated on johnsongrass and tomato seedling growth in greenhouse conditions. The lowest johnsongrass density was recorded in black radish and garden cress with mulch (106.7 and 97.2 number m-2). Black radish and garden cress with mulch achieved johnsongrass control efficiency of 80.2 and 84.0% compared to those without mulch 56.8 and 58.2%. The effect of all treatments was positive in increasing the quantity and improving the quality of tomato production. The results of greenhouse experiments showed that high concentrations (10%) of black radish and garden cress extracts achieved high levels in preventing the germination and growth of johnsongrass. In these treatments, johnsongrass seeds and rhizomes germination rates were 17.5 and 7.5%, 20.0 and 12.5% respectively. GC-MS analysis showed that five isothiocyanates (ITCs) were in black radish, and their total percentages were 40.4%. In the garden cress, it was found that there is only one ITC with a percentage of 61.0%. Black radish and garden cress effectively inhibit the germination and growth of Johnsongrass due to their allelopathy effects. Sustainable management of johnsongrass can be achieved by introducing these plants into a crop rotation which may be an alternative or reduce the use of herbicides.