If you want published scientific information go to,
Smart, R. M. and Barko, J. W. 1985. Laboratory culture of
submersed freshwater macrophytes on natural sediments. Aquatic Botany 21;
251 to 263.
Barko, J. W. and Smart, R. M. 1986. Sediment-related mechanisms
of growth limitation in submersed macrophytes. Ecology 67; 1328 to 1340.
As I mentioned recently, laterite is by definition a highly weathered red
clay which contains primarily iron and aluminum. However, having no first
hand experience with laterite (textbooks and lectures only) I cant really
say for certain that this is ALL that it contains ... Im sure K. Schoeler
can fill you in with more detail.