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Title: Allelopathic, Autotoxic, and Hormetic Effects of Post-harvest Sugarcane Residue

item Viator, Ryan
item Johnson, Richard
item Grimm, Casey
item Richard Jr, Edward

Submitted to: American Society of Sugar Cane Technologists
Publication Type: Abstract Only
Publication Acceptance Date: 5/9/2007
Publication Date: 6/11/2007
Citation: Viator, R.P., Johnson, R.M., Grimm, C.C., Richard Jr, E.P. 2007. Allelopathic, Autotoxic, and Hormetic Effects of Post-harvest Sugarcane Residue [abstract]. Journal of the American Society of Sugar Cane Technologists. 27:69.

Interpretive Summary:

Technical Abstract: With green sugarcane (interspecific hybrids of Saccharum spp.) harvesting, 6 to 24 tonne/ha of post-harvest residue is deposited on the field surface covering the sugarcane stubble that must reemerge for several ratoon crops. The objectives of this research were to: 1) determine if post-harvest residue possesses allelopathic, autotoxic, and hormetic properties, 2) determine the interaction of soil type with possible autotoxic effects, and 3) identify a reliable indicator species. In order to determine the effects of post harvest residue on the growth of sugarcane and other species, a leachates were extracted from residue using water. Extract concentrations consisted of 0, 0.1, 10, 25, and 100% of the original solution of a 1:28 tissue to water extract. The higher concentrations of residue extracts exhibited autotoxicity by delaying early leaf development. The lower extract concentration of 10% increased sugarcane bud germination by 45% compared to the control indicating hormetic effects. Allelopathic activity on tall morninglory (Ipomoea hederacea) was more pronounced on a light soil; germination and radical length were reduced by all concentrations by an average of 42% and 8mm, respectively, compared to the control. Seedling dry weights were reduced by an average of 10 mg by the 10, 25, and 100 % extract concentrations relative to the control. On the heavy soil, only the 100% concentration reduced radical length and weight by 5 mm and 4 mg, respectively, relative to the control. Allelopathic effects on oat (Avena nuda), rye (Secale cereale), and tomato (Lycopersicon esculentum) showed poor correlation with the autotoxic effects on sugarcane. Chemical analysis by GC/MS indicated the extract contained benzoic acid. Further studies are needed to establish the impact of benzoic acid in natural settings. The presence of both hormetic and autotoxic effects of post-harvest residue may explain why yield effects are sometimes inconsistent. Environmental conditions will influence the level of residue decomposition and therefore the level of benzoic acid present in the germinating bud zone. Moreover, autotoxicity may explain why sometimes mechanical removal of the residue from the row-top into the wheel furrow produces lower yields than a field burn.