Allelopathic Effects of Sandbur Leachate on Switchgrass Germination: Observations

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Abstract
Switchgrass (Panicum virgatum L.) establishment from seed was limited by current-year''s growth of sandbur [Cenchrus longispinus (Hack.) Fern.] in the Nebraska [USA] Sandhills. Stand reduction was greater than other warm-season grasses seeded at the same time, indicating possible allelopathy. Germination studies were conducted to evaluate potential sandbur allelopathy with switchgrass. Fresh sandbur plant material was extracted with distilled water for 24 hours. Root, shoot, and whole plant leachate (2% w/v) from sandbur plants collected between the vegetative and culm elongation stage and whole plant leachate (2, 4% w/v) from vegetative or mature plants was used. Switchgrass germination was not influenced by root, shoot, or whole plant leachate from sandbur plants composited over phenological stages. However, leachate reduced the length of the primary root and increased shoot length measured at 11 days. Generally, the response was greater with vegetative sandbur compared to mature and with the higher leachate concentration. Whole plant leachate (4% w/v) from vegetative sandbur reduced switchgrass germination compared to mature plant leachate. The relatively rapid development of a sandbur cover prior to switchgrass seed germination on sandy sites may affect switchgrass germination and early root development through an allelopathic interaction. Since tillage promotes rapid sandbur development, no-till seedings should be considered for switchgrass on sandy spoils.