James H. Houx

Effects of shade on growth and nodulation on three native legumes with potential for use in agroforestry

In the Midwest US, native legume species adapted to savanna environments may grow well under varying shade conditions. These species may be ideal for use within tree rows in alley-cropping practices and on tree plantations by providing biologically fixed nitrogen, ground cover, and wildlife food and habitat. A greenhouse experiment was conducted to evaluate the effect of 3 different light levels (100%, 45%, 20%) on the growth and nodulation of 3 Desmodium (Fabaceae) species: Hoary ticktrefoil (D. canescens (L.) DC.), Showy ticktrefoil (D. canadense (L.) DC.), and Illinois ticktrefoil (D. illinoense A. Gray). All species produced equal amounts of dry matter at 45% and 100% light, but significantly less dry matter at 20% light. All species had greater or equal concentrations of nitrogen (N) at 20% light compared with 45% or 100% light. The number of nodules per gram of plant dry weight and nodule dry weight was similar at all light levels within each species. A significant species x light interaction was found for the number of nodules per plant because nodule number decreased in both D. canescens and D. canadense but not in D. illinoense for plants grown at 20% in comparison with 45% light. The number of nodules per plant and the number of nodules per gram of plant dry weight were lower under all light conditions for D. illinoense compared with the other species. Results indicate that these native legumes grow as well at 45% light as they do at 100% light, and shade does not reduce N concentration.Houx JH III, McGraw RL, Fritschi FB, Navarrete-Tindall NE. 2009. Effects of shade on growth and nodulation of three native legumes with potential for use in agroforestry. Native Plants Journal 10(3): 232–238.