Allelopathic Effect of Rice Straw Extract and Its Potential Use as a Bioherbicide
Mai Beauty John
Department of Agronomy, Yezin Agricultural University, Yezin, Nay Pyi Taw, Myanmar.
Ei Han Kyaw *
Department of Agronomy, Yezin Agricultural University, Yezin, Nay Pyi Taw, Myanmar.
Thu Zar
Department of Agronomy, Yezin Agricultural University, Yezin, Nay Pyi Taw, Myanmar.
Aung Win
Advanced Center for Agricultural Research and Education, (YAU), Yezin, Nay Pyi Taw, Myanmar.
Htay Htay Oo
Department of Agronomy, Yezin Agricultural University, Yezin, Nay Pyi Taw, Myanmar.
*Author to whom correspondence should be addressed.
Abstract
Rice straw contains allelochemicals that may contribute to sustainable weed management by suppressing weed growth and development. This study evaluated the allelopathic effect of rice straw extract from the Myanmar rice variety Paw San Yin (Oryza sativa L.) on lettuce (Lactuca sativa L.), four weed species, and two rice varieties under laboratory conditions at the Experiment and Lecture Building (II), Department of Agronomy, Yezin Agricultural University, Nay Pyi Taw, Myanmar, during May–September 2025. Two experiments were conducted in a randomised complete block design (RCBD) with four and five replications, respectively. Experiment I (May–July 2025) involved lettuce treated with aqueous rice straw extracts at 0, 10, 30, 50, and 100 g L⁻¹. Experiment II (July–September 2025) included barnyard grass (Echinochloa crus-galli (L.) P. Beauv.), red sprangletop (Leptochloa chinensis (L.) Nees), long-fruited primrose willow (Ludwigia octovalvis (Jacq.) P.H.Raven), sessile joyweed (Alternanthera sessilis (L.) R.Br. ex-DC.), and two rice varieties (Sin Thu Kha and Paw San Yin), treated with 0, 50, 100, and 150 g L⁻¹ extract concentrations. Germination percentage, shoot length (mm), root length (mm), fresh weight (mg), and dry weight (mg) were recorded. The results showed that rice straw extract significantly inhibited seed germination, seedling growth, fresh and dry weights of seedlings in a concentration-dependent manner. Complete inhibition of lettuce growth was observed at 100 g L⁻¹. In Experiment II, broadleaf weeds were more sensitive than grasses, with complete suppression of L. octovalvis and A. sessilis at higher concentrations. Root growth was more strongly inhibited by the allelochemicals in rice straw than shoot growth across all species. The extract also exhibited noticeable autotoxic effects on both rice varieties. Overall, the findings demonstrated that rice straw extract possesses strong allelopathic activity and has potential as a natural bioherbicide for weed management.
Keywords: Allelopathy, rice straw extract, weed suppression, autotoxicity, sustainable weed management