Sugarcane Field Residue and Root Allelopathic Impact on Weed Seed Germination

Allelopathy, the chemical interaction between plants, may result in the inhibition of plant growth and development, which can include compounds released from a crop that adversely impact weed species. The objective of this research was to determine the allelopathic impact of sugarcane (Saccharum officinarum) field residue and root water extracts on seed germination of three weed species. Red morningglory (Ipomoea coccinea L.), redroot pigweed (Amaranthus retroflexus L.), and spiny amaranth (Amaranthus spinosus L.)] seeds were treated with five extract concentrations (0, 12.5, 25, 50, and 100 g/L) from either sugarcane field residue or sugarcane root extracts. The field residue and roots were from sugarcane variety ‘HoCP 96-540’ plant cane. Germination generally decreased with increasing sugarcane field residue extract concentrations in the three weed species tested. At the highest residue concentration (100 g/L), red morningglory, redroot pigweed, and spiny amaranth germination decreased by 29%, 17.5% and 80.5%, respectively. Germination generally decreased with increasing sugarcane root extract concentrations in red morningglory and redroot pigweed, but not with spiny amaranth. The highest root concentration (100 g/L) decreased red morningglory and redroot pigweed germination by 19.5% and 18.5%, respectively. This research provides the first bioassay demonstrating that sugarcane root extracts have allelopathic activity, and specifically in respect to red morningglory and redroot pigweed germination. Future research should investigate the allelopathic compounds present in the sugarcane field residue and roots, determine if the same allelopathic compounds are present and in similar concentrations among other sugarcane varieties, and further examine which weed species may be susceptible to the allelopathic compounds present in sugarcane roots.