Eastern gamagrass (Tripsacum dactyloides) root penetration into and chemical properties of claypan soils

Abstract

Claypans restrict rooting depth and availability of moisture and nutrients to plants during periods of drought. Eastern gamagrass [Tripsacum dactyloides var. dactyloides (L.) L] often remains green during summer droughts, while other plants turn brown. Questions arose whether eastern gamagrass roots could penetrate claypans to obtain needed moisture. Pits were dug (2m deep) under eastern gamagrass plants that had been growing 50+ and 5+ years at two sites in Missouri. Clay contents were 30 to 50% in soil layers below 30 cm, and moisture was not limiting in these deep soil layers. Soil pHCa, in the lower soil layers, except at 180 cm, was below 5.0, and in some cases near 4.0. Extractable Al was especially high in the 90 and 120 cm deep soil layers where pH was low. Extractable Ca, Mg, and K increased with soil depth. The eastern gamagrass roots effectively penetrated claypan soils. Root lengths and root weights were extensive to 180 cm depth, and decreased from the surface with soil depth. Roots of eastern gamagrass were aerenchymous (having cellular compartments which allow air movement) at all depths, were mycorrhizal to at least 150 cm depth, and had relatively high tolerance to acidic Al toxic Tatum subsoil (Typic Hapludult) and toxic levels of Al in nutrient solution. The eastern gamagrass roots also provided root channels through claypans, which could enable new eastern gamagrass or other plant roots to grow into deeper soil layers.