Sugarcane Crop Residue and Bagasse Allelopathic Impact on Oat (Avena sative L.), Tall Morningglory (Ipomoea purpurea L. Roth), and Redroot Pigweed (Amaranthus retroflexus L.) Germination

Allelopathy, the chemical interaction between plants, may result in the inhibition of plant growth and development, and includes compounds released from a primary crop that adversely impact crop or weed species. The objective of this research was to observe the allelopathic impact of sugarcane (Saccharum sp.) post-harvest crop residue and mill bagasse leachate on seed germination of three other plant species. Oat (Avena sative L.) var. ‘Corral’, tall morningglory (Ipomoea purpurea L. Roth), and redroot pigweed (Amaranthus retroflexus L.) seeds were treated with 5 leachate concentrations (0, 12.5, 25, 50, and 100 g/L) from either sugarcane crop residue or sugarcane bagasse. Each experiment was repeated twice (Experiment 1 & 2) with each plant species, leachate concentrations, and leachate source (sugarcane crop residue and mill bagasse). The impact of leachates from sugarcane variety ‘HoCP 96-540’ crop residue and sugarcane bagasse differed by the species evaluated (oat, morningglory, and redroot pigweed), the leachate source (crop residue vs. bagasse), and leachate concentration (0 to 100 g/L). Oat germination was not affected leachate source or concentration. Germination for both weed species, tall morningglory and redroot pigweed, were adversely affected by leachate source and concentration. In both cases, the sugarcane crop residue leachate had a greater deleterious impact on germination than did the bagasse leachate. The response to the leachates was more consistent and severe for tall morningglory germination than redroot pigweed germination. Averaged across experiments, the 12.5 g/L crop residue concentration decreased the tall morningglory germination to 17% compared to 34% germination for the bagasse leachate, and the 100 g/L residue concentration reduce germination to 6% compared to 19% for bagasse 100 g/L bagasse concentration. The 100 g/L concentration of crop residue reduced redroot pigweed germination by 13% (Experiment 1) and 27% (Experiment 2), while the bagasse leachate reduced germination by 5% (Experiment 1) and 15% (Experiment 2). Future research should investigate the allelopathic compounds present in the sugarcane crop residue and bagasse, determine if the same allelopathic compounds are present and in the same concentration among other sugarcane varieties, and further examine which weed and crop species may be vulnerable to the allelopathic compounds present in sugarcane crop residue and bagasse.