Legumes increase growth and alter foliar nutrient levels of black walnut saplings

Van Sambeek, J.W., Ponder, F., Jr. and Rietveld, W.J., 1986. Legumes increase growth and alter foliar nutrient levels of black walnut. For. Ecol. Manage., 17: 159-167. Differences in herbaceous competition, growth, soil, and foliar nutrient levels were compared for black walnut (Juglans nigra L.) saplings growing on an upland and a bottomland site in southern Illinois, with covers of five different herbaceous legumes or naturally occurring forbs. Hairy vetch ( Vicia viUosa Roth. ) increased walnut height and diameter growth on both sites when compared to walnut growing in the naturally revegetated plots. Growth trends in the other four covers were mixed. All five legumes suppressed growth of other herbaceous vegetation for one or more summers. Only hairy vetch increased soil nitrate nitrogen after one growing season on both sites. After three growing seasons, crownvetch (CoroniUa varia L.) and sericsa lespedeza (Lespedeza cuneata (Dumont) G. Dons.) have increased soil nitrate nitrogen on the upland plantation. Walnut foliar nitrogen concentration was the highest for trees growing in hairy vetch and crownvetch covers after three growingssasons.