Response of two perennial herbaceous Texas legumes to shade

Abstract

Very few perennial herbaceous legumes have been developed for native seed mixes in the southern Great Plains, and none are specifically sold for forest understory reseeding. This study looked at shade tolerance of tropical puff (Neptunia pubescens Benth. var. microcarpa (Rose) Windler [Fabaceae]) and dollar snout-bean (Rhynchosia americana (Houst. ex Mill.) M.C. Metz [Fabaceae]) over 3 growing seasons. Pod production declined (P = 0.001) only at 80% shade and dollar snout-bean branch length and herbage production increased (P < 0.08) at moderate shade levels compared with open sunlight and in contrast to tropical puff that showed no positive responses to shade. Neutral detergent fiber and acid detergent fiber increased (P = 0.001) at 80% shade while acid detergent lignin decreased (P = 0.02) under shade except for dollar snout-bean at high levels of shade. Nitrogen and carbon concentrations increased (P = 0.10) under shade for both species but carbon decreased (P = 0.10) at 80% shade in the snout-bean. Both species should be useful for inclusion in seed mixes under tree and brush canopies because they tolerate and even thrive under moderate shade. Tropical puff shows greater potential for nutritive value for ruminant nutrition due to lower fiber and greater nitrogen concentrations compared with the snout-bean.