Submitted to: International Society of Root Research Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 7/17/1996
Publication Date: N/A
Technical Abstract: Nearly four million hectares of soil in central-eastern Missouri and southern Illinois have claypans. These claypans restrict root growth into deeper soil layers so moisture and nutrients during droughty periods are less available to plants. Eastern gamagrass (EG) [Tripsacum dactyloides (L.) L.] remained green during droughty summer months, while other plants turned brown. Questions arose whether roots of EG plants could penetrate claypans to obtain needed moisture. Pits were dug (2-m deep) under EG plants that had been growing for several years at two sites. Roots of EG were noted as deep as 180 cm. Total root length and root weights decreased from the surface with soil depth, yet roots were fairly extensive even at 180 cm. Roots of EG were aerenchymous (cellular compartments allowing air to move) at all depths, were mycorrhizal to at least 150 cm depth, and had high tolerance to toxic levels of Al. Clay contents were 30 to 50% in soil layers below 30 cm, and moisture was not limiting in the deep soil layers. Soil pH in the lower soil layers, except at 180 cm, was below 5.0, and in some cases close to 4.0. Exchangeable Al was especially high in soil layers where pH was low. Exchangeable Ca, Mg, and K increased with soil depth. Roots of soybean [Glycine max (L.) Merr.] grown at a site where EG had been grown two years previously had deeper roots than those grown at other sites under conventional and no-till conditions. The EG roots effectively penetrated claypans providing moisture through droughty periods. The EG roots also provided macropores through claypans for which new EG or other plant species roots could grow to deeper soil layers.