Allelopathic Effects of Leucaena leucocephala and Carica papaya Leaf Extracts on Weed Suppression and Yield of Japanese Cucumber (Cucumis sativus L.)

This study aims to evaluate the efficacy of Leucaena leucocephala and Carica papaya leaf extracts as bioherbicides for controlling weeds and enhancing the growth and yield of Japanese cucumber (Cucumis sativus L. var. Japanese) across different extract types and concentrations.

A randomized complete block design (RCBD) experiment consisting of six treatment groups and one control group was used for a single factor. The experiment was replicated three times and resulted in a total of 21 experimental plots. The treatment groups included the control group as well as extract concentrations of 30%, 45% and 60% obtained from young leaf material of Leucaena leucocephala and mature green leaf material of Carica papaya. The dominant weed species found throughout the cucumber plots and the subject of the weeding treatment groups was Cyperus rotundus. Treatment for weeds in the plots was provided via sprays that were applied to weeds prior to their early vegetative stage. Sprays continued until the total amount of spray volume was 216 mL per plot or until the surface of the soil was uniformly moistened. Care was taken while spraying to prevent direct contact between the extracts and the cucumber plant by directing the sprays toward the weed canopy and the soil surface. Data collection and statistical analysis of data were completed using DMRT at a 95% confidence interval. This study was conducted from March through May of 2025 in Sleman, Indonesia.

The application of 45% leaf extract demonstrated the most effective weed control and promoted optimal growth of Japanese cucumbers, resulting in a yield of approximately 28.36 tons per hectare during the study. Weeds began to emerge at 7 days after planting (DAP). Spraying was conducted at 14 DAP, when weeds were already present and no synthetic herbicides were applied during the experiment. These findings highlight the potential of Leucaena leucocephala and Carica papaya leaf extracts as effective, eco-friendly bioherbicides that suppress weed interference without compromising crop performance. Their ease of preparation and availability as agricultural by-products offer a sustainable weed-management alternative for farmers and further research across diverse conditions and cropping systems is recommended to expand their practical application.